The current name does not explain the meaning well. So give it a better
name "retry_walk" to show that we are trying the walk again.
This was suggested by Ingo Molnar.
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Avoid two step jump to the error handling part. This eliminates the use
of the variables present and rsvd_fault.
We also use the const type qualifier to show that write/user/fetch_fault
do not change in the function.
Both of these were suggested by Ingo Molnar.
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
On 3.0-rc1 I get
In file included from arch/x86/kvm/mmu.c:2856:
arch/x86/kvm/paging_tmpl.h: In function ‘paging32_walk_addr_generic’:
arch/x86/kvm/paging_tmpl.h:124: warning: ‘ptep_user’ may be used uninitialized in this function
In file included from arch/x86/kvm/mmu.c:2852:
arch/x86/kvm/paging_tmpl.h: In function ‘paging64_walk_addr_generic’:
arch/x86/kvm/paging_tmpl.h:124: warning: ‘ptep_user’ may be used uninitialized in this function
caused by 6e2ca7d180. According to Takuya
Yoshikawa, ptep_user won't be used uninitialized so shut up gcc.
Cc: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Link: http://lkml.kernel.org/r/20110530094604.GC21833@liondog.tnic
Signed-off-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Avi Kivity <avi@redhat.com>
The address of the gpte was already calculated and stored in ptep_user
before entering cmpxchg_gpte().
This patch makes cmpxchg_gpte() to use that to make it clear that we
are using the same address during walk_addr_generic().
Note that the unlikely annotations are used to show that the conditions
are something unusual rather than for performance.
Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
This way, we can avoid checking the user space address many times when
we read the guest memory.
Although we can do the same for write if we check which slots are
writable, we do not care write now: reading the guest memory happens
more often than writing.
[avi: change VERIFY_READ to VERIFY_WRITE]
Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Avi Kivity <avi@redhat.com>
When we optimized walk_addr_generic() by not using the generic guest
memory reader, we replaced copy_from_user() with get_user():
commit e30d2a170506830d5eef5e9d7990c5aedf1b0a51
KVM: MMU: Optimize guest page table walk
commit 15e2ac9a43d4d7d08088e404fddf2533a8e7d52e
KVM: MMU: Fix 64-bit paging breakage on x86_32
But as Andi pointed out later, copy_from_user() does the same as
get_user() as long as we give a constant size to it.
So we use copy_from_user() to clean up the code.
The only, noticeable, regression introduced by this is 64-bit gpte
reading on x86_32 hosts needed for PAE guests.
But this can be mitigated by implementing 8-byte get_user() for x86_32,
if needed.
Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Avi Kivity <avi@redhat.com>
Fix regression introduced by
commit e30d2a170506830d5eef5e9d7990c5aedf1b0a51
KVM: MMU: Optimize guest page table walk
On x86_32, get_user() does not support 64-bit values and we fail to
build KVM at the point of 64-bit paging.
This patch fixes this by using get_user() twice for that condition.
Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Reported-by: Jan Kiszka <jan.kiszka@web.de>
Signed-off-by: Avi Kivity <avi@redhat.com>
walk_addr_generic() is a hot path and is also hard for the cpu to predict -
some of the parameters (fetch_fault in particular) vary wildly from
invocation to invocation.
Add unlikely() annotations where appropriate; all walk failures are
considered unlikely, as are cases where we have to mark the accessed or
dirty bit, as they are slow paths both in kvm and on real processors.
Signed-off-by: Avi Kivity <avi@redhat.com>
This patch optimizes the guest page table walk by using get_user()
instead of copy_from_user().
With this patch applied, paging64_walk_addr_generic() has become
about 0.5us to 1.0us faster on my Phenom II machine with NPT on.
Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Avi Kivity <avi@redhat.com>
This patch makes the cmpxchg_gpte() function aware of the
difference between l1-gfns and l2-gfns when nested
virtualization is in use. This fixes a potential
data-corruption problem in the l1-guest and makes the code
work correct (at least as correct as the hardware which is
emulated in this code) again.
Cc: stable@kernel.org
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
The mmu_seq verification can be removed since we get the pfn in the
protection of mmu_lock.
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
* 'x86-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
x86: Flush TLB if PGD entry is changed in i386 PAE mode
x86, dumpstack: Correct stack dump info when frame pointer is available
x86: Clean up csum-copy_64.S a bit
x86: Fix common misspellings
x86: Fix misspelling and align params
x86: Use PentiumPro-optimized partial_csum() on VIA C7
They were generated by 'codespell' and then manually reviewed.
Signed-off-by: Lucas De Marchi <lucas.demarchi@profusion.mobi>
Cc: trivial@kernel.org
LKML-Reference: <1300389856-1099-3-git-send-email-lucas.demarchi@profusion.mobi>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This patch does:
- call vcpu->arch.mmu.update_pte directly
- use gfn_to_pfn_atomic in update_pte path
The suggestion is from Avi.
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
No need to record the gfn to verifier the pte has the same mode as
current vcpu, it's because we only speculatively update the pte only
if the pte and vcpu have the same mode
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
This should work for both hugetlbfs and transparent hugepages.
[akpm@linux-foundation.org: bring forward PageTransCompound() addition for bisectability]
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: Avi Kivity <avi@redhat.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Move the operation of 'writable' to set_spte() to clean up code
[avi: remove unneeded booleanification]
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
If KVM sees a read-only host page, it will map it as read-only to prevent
breaking a COW. However, if the page was part of a large guest page, KVM
incorrectly extends the write protection to the entire large page frame
instead of limiting it to the normal host page.
This results in the instantiation of a new shadow page with read-only access.
If this happens for a MOVS instruction that moves memory between two normal
pages, within a single large page frame, and mapped within the guest as a
large page, and if, in addition, the source operand is not writeable in the
host (perhaps due to KSM), then KVM will instantiate a read-only direct
shadow page, instantiate an spte for the source operand, then instantiate
a new read/write direct shadow page and instantiate an spte for the
destination operand. Since these two sptes are in different shadow pages,
MOVS will never see them at the same time and the guest will not make
progress.
Fix by mapping the direct shadow page read/write, and only marking the
host page read-only.
Signed-off-by: Avi Kivity <avi@redhat.com>
Retry #PF for softmmu only when the current vcpu has the same cr3 as the time
when #PF occurs
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
It's the speculative path if 'no_apf = 1' and we will specially handle this
speculative path in the later patch, so 'prefault' is better to fit the sense.
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Currently page fault cr2 and nesting infomation are carried outside
the fault data structure. Instead they are placed in the vcpu struct,
which results in confusion as global variables are manipulated instead
of passing parameters.
Fix this issue by adding address and nested fields to struct x86_exception,
so this struct can carry all information associated with a fault.
Signed-off-by: Avi Kivity <avi@redhat.com>
Tested-by: Joerg Roedel <joerg.roedel@amd.com>
Tested-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Quote from Avi:
| I don't think we need to flush immediately; set a "tlb dirty" bit somewhere
| that is cleareded when we flush the tlb. kvm_mmu_notifier_invalidate_page()
| can consult the bit and force a flush if set.
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Introduce a common function to map invalid gpte
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Remove it since we can judge it by using sp->unsync
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Rename it to fit its sense better
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
We should flush all tlbs after drop spte on sync_page path since
Quote from Avi:
| sync_page
| drop_spte
| kvm_mmu_notifier_invalidate_page
| kvm_unmap_rmapp
| spte doesn't exist -> no flush
| page is freed
| guest can write into freed page?
KVM-Stable-Tag.
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
If reserved bit is set, we need inject the #PF with PFEC.RSVD=1,
but shadow_notrap_nonpresent_pte injects #PF with PFEC.RSVD=0 only
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
As suggested by Andrea, pass r/w error code to gup(), upgrading read fault
to writable if host pte allows it.
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
When page is swapped in it is mapped into guest memory only after guest
tries to access it again and generate another fault. To save this fault
we can map it immediately since we know that guest is going to access
the page. Do it only when tdp is enabled for now. Shadow paging case is
more complicated. CR[034] and EFER registers should be switched before
doing mapping and then switched back.
Acked-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
If a guest accesses swapped out memory do not swap it in from vcpu thread
context. Schedule work to do swapping and put vcpu into halted state
instead.
Interrupts will still be delivered to the guest and if interrupt will
cause reschedule guest will continue to run another task.
[avi: remove call to get_user_pages_noio(), nacked by Linus; this
makes everything synchrnous again]
Acked-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Move access code parsing from caller site to FNAME(walk_addr) function
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
With Nested Paging emulation the NX state between the two
MMU contexts may differ. To make sure that always the right
fault error code is recorded this patch moves the NX state
into struct kvm_mmu so that the code can distinguish between
L1 and L2 NX state.
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
This function is implemented to load the pdptr pointers of
the currently running guest (l1 or l2 guest). Therefore it
takes care about the current paging mode and can read pdptrs
out of l2 guest physical memory.
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
This patch uses kvm_read_guest_page_tdp to make the
walk_addr_generic functions suitable for two-level page
table walking.
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
This patch adds the functions to do a nested l2_gva to
l1_gpa page table walk.
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
This is the first patch in the series towards a generic
walk_addr implementation which could walk two-dimensional
page tables in the end. In this first step the walk_addr
function is renamed into walk_addr_generic which takes a
mmu context as an additional parameter.
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
This patch introduces a struct with two new fields in
vcpu_arch for x86:
* fault.address
* fault.error_code
This will be used to correctly propagate page faults back
into the guest when we could have either an ordinary page
fault or a nested page fault. In the case of a nested page
fault the fault-address is different from the original
address that should be walked. So we need to keep track
about the real fault-address.
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
This patch changes is_rsvd_bits_set() function prototype to
take only a kvm_mmu context instead of a full vcpu.
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
This function pointer in the MMU context is required to
implement Nested Nested Paging.
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
The walk_addr function checks for !is_long_mode in its 64
bit version. But what is meant here is a check for pae
paging. Change the condition to really check for pae paging
so that it also works with nested nested paging.
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Add a r/w module parameter named 'mmu_audit', it can control audit
enable/disable:
enable:
echo 1 > /sys/module/kvm/parameters/mmu_audit
disable:
echo 0 > /sys/module/kvm/parameters/mmu_audit
This patch not change the logic
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
The audit code reports some sp not write protected in current code, it's just the
bug in audit_write_protection(), since:
- the invalid sp not need write protected
- using uninitialize local variable('gfn')
- call kvm_mmu_audit() out of mmu_lock's protection
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Support prefetch ptes when intercept guest #PF, avoid to #PF by later
access
If we meet any failure in the prefetch path, we will exit it and
not try other ptes to avoid become heavy path
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
In the speculative path, we should check guest pte's reserved bits just as
the real processor does
Reported-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
'level' and 'sptep' are aliases for 'interator.level' and 'iterator.sptep', no
need for them.
Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Currently, when we fetch an spte, we only verify that gptes match those that
the walker saw if we build new shadow pages for them.
However, this misses the following race:
vcpu1 vcpu2
walk
change gpte
walk
instantiate sp
fetch existing sp
Fix by validating every gpte, regardless of whether it is used for building
a new sp or not.
Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Partition the function into three sections:
- fetching indirect shadow pages (host_level > guest_level)
- fetching direct shadow pages (page_level < host_level <= guest_level)
- the final spte (page_level == host_level)
Instead of the current spaghetti.
A slight change from the original code is that we call validate_direct_spte()
more often: previously we called it only for gw->level, now we also call it for
lower levels. The change should have no effect.
[xiao: fix regression caused by validate_direct_spte() called too late]
Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Move the code to check whether a gpte has changed since we fetched it into
a helper.
Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Add a helper to verify that a direct shadow page is valid wrt the required
access permissions; drop the page if it is not valid.
Reviewed-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
To clarify spte fetching code, move large spte handling into a helper.
Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
To simplify the process of fetching an spte, add a helper that links
a shadow page to an spte.
Reviewed-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Real hardware disregards permission errors when computing page fault error
code bit 0 (page present). Do the same.
Reviewed-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Bit 4 of the page fault error code is set only if EFER.NX is set.
Reviewed-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
When we call rmap_remove(), we (almost) always immediately follow it by
an __set_spte() to a nonpresent pte. Since we need to perform the two
operations atomically, to avoid losing the dirty and accessed bits, introduce
a helper drop_spte() and convert all call sites.
The operation is still nonatomic at this point.
Signed-off-by: Avi Kivity <avi@redhat.com>
Cleanup this function that we are already get the direct sp's access
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
If the mapping is writable but the dirty flag is not set, we will find
the read-only direct sp and setup the mapping, then if the write #PF
occur, we will mark this mapping writable in the read-only direct sp,
now, other real read-only mapping will happily write it without #PF.
It may hurt guest's COW
Fixed by re-install the mapping when write #PF occur.
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
In no-direct mapping, we mark sp is 'direct' when we mapping the
guest's larger page, but its access is encoded form upper page-struct
entire not include the last mapping, it will cause access conflict.
For example, have this mapping:
[W]
/ PDE1 -> |---|
P[W] | | LPA
\ PDE2 -> |---|
[R]
P have two children, PDE1 and PDE2, both PDE1 and PDE2 mapping the
same lage page(LPA). The P's access is WR, PDE1's access is WR,
PDE2's access is RO(just consider read-write permissions here)
When guest access PDE1, we will create a direct sp for LPA, the sp's
access is from P, is W, then we will mark the ptes is W in this sp.
Then, guest access PDE2, we will find LPA's shadow page, is the same as
PDE's, and mark the ptes is RO.
So, if guest access PDE1, the incorrect #PF is occured.
Fixed by encode the last mapping access into direct shadow page
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
As advertised in feature-removal-schedule.txt. Equivalent support is provided
by overlapping memory regions.
Signed-off-by: Avi Kivity <avi@redhat.com>
If the sync-sp just sync transient, don't mark its pte notrap
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Rename 'page' and 'shadow_page' to 'sp' to better fit the context
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
In Documentation/kvm/mmu.txt:
gfn:
Either the guest page table containing the translations shadowed by this
page, or the base page frame for linear translations. See role.direct.
But in function FNAME(fetch)(), sp->gfn is incorrect when one of following
situations occurred:
1) guest is 32bit paging and the guest PDE maps a 4-MByte page
(backed by 4k host pages), FNAME(fetch)() miss handling the quadrant.
And if guest use pse-36, "table_gfn = gpte_to_gfn(gw->ptes[level - delta]);"
is incorrect.
2) guest is long mode paging and the guest PDPTE maps a 1-GByte page
(backed by 4k or 2M host pages).
So we fix it to suit to the document and suit to the code which
requires sp->gfn correct when sp->role.direct=1.
We use the goal mapping gfn(gw->gfn) to calculate the base page frame
for linear translations, it is simple and easy to be understood.
Reported-by: Marcelo Tosatti <mtosatti@redhat.com>
Reported-by: Gui Jianfeng <guijianfeng@cn.fujitsu.com>
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
When sp->role.direct is set, sp->gfns does not contain any essential
information, leaf sptes reachable from this sp are for a continuous
guest physical memory range (a linear range).
So sp->gfns[i] (if it was set) equals to sp->gfn + i. (PT_PAGE_TABLE_LEVEL)
Obviously, it is not essential information, we can calculate it when need.
It means we don't need sp->gfns when sp->role.direct=1,
Thus we can save one page usage for every kvm_mmu_page.
Note:
Access to sp->gfns must be wrapped by kvm_mmu_page_get_gfn()
or kvm_mmu_page_set_gfn().
It is only exposed in FNAME(sync_page).
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Only unsync pages need updated at invlpg time since other shadow
pages are write-protected
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Sometime cmpxchg_gpte doesn't modify gpte, in such case, don't mark
page table page as dirty.
Signed-off-by: Gui Jianfeng <guijianfeng@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
In common cases, guest SRAO MCE will cause corresponding poisoned page
be un-mapped and SIGBUS be sent to QEMU-KVM, then QEMU-KVM will relay
the MCE to guest OS.
But it is reported that if the poisoned page is accessed in guest
after unmapping and before MCE is relayed to guest OS, userspace will
be killed.
The reason is as follows. Because poisoned page has been un-mapped,
guest access will cause guest exit and kvm_mmu_page_fault will be
called. kvm_mmu_page_fault can not get the poisoned page for fault
address, so kernel and user space MMIO processing is tried in turn. In
user MMIO processing, poisoned page is accessed again, then userspace
is killed by force_sig_info.
To fix the bug, kvm_mmu_page_fault send HWPOISON signal to QEMU-KVM
and do not try kernel and user space MMIO processing for poisoned
page.
[xiao: fix warning introduced by avi]
Reported-by: Max Asbock <masbock@linux.vnet.ibm.com>
Signed-off-by: Huang Ying <ying.huang@intel.com>
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
In no-direct mapping, we mark sp is 'direct' when we mapping the
guest's larger page, but its access is encoded form upper page-struct
entire not include the last mapping, it will cause access conflict.
For example, have this mapping:
[W]
/ PDE1 -> |---|
P[W] | | LPA
\ PDE2 -> |---|
[R]
P have two children, PDE1 and PDE2, both PDE1 and PDE2 mapping the
same lage page(LPA). The P's access is WR, PDE1's access is WR,
PDE2's access is RO(just consider read-write permissions here)
When guest access PDE1, we will create a direct sp for LPA, the sp's
access is from P, is W, then we will mark the ptes is W in this sp.
Then, guest access PDE2, we will find LPA's shadow page, is the same as
PDE's, and mark the ptes is RO.
So, if guest access PDE1, the incorrect #PF is occured.
Fixed by encode the last mapping access into direct shadow page
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
If the guest is 32-bit, we should use 'quadrant' to adjust gpa
offset
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Make use of is_large_pte() instead of checking PT_PAGE_SIZE_MASK
bit directly.
Signed-off-by: Gui Jianfeng <guijianfeng@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Move first pte address calculation out of loop to save some cycles.
Signed-off-by: Gui Jianfeng <guijianfeng@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
After is_rsvd_bits_set() checks, EFER.NXE must be enabled if NX bit is seted
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Commit fb341f57 removed the pte prefetch on guest invlpg, citing guest races.
However, the SDM is adamant that prefetch is allowed:
"The processor may create entries in paging-structure caches for
translations required for prefetches and for accesses that are a
result of speculative execution that would never actually occur
in the executed code path."
And, in fact, there was a race in the prefetch code: we picked up the pte
without the mmu lock held, so an older invlpg could install the pte over
a newer invlpg.
Reinstate the prefetch logic, but this time note whether another invlpg has
executed using a counter. If a race occured, do not install the pte.
Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
The update_pte() path currently uses a nontrapping spte when a nonpresent
(or nonaccessed) gpte is written. This is fine since at present it is only
used on sync pages. However, on an unsync page this will cause an endless
fault loop as the guest is under no obligation to invlpg a gpte that
transitions from nonpresent to present.
Needed for the next patch which reinstates update_pte() on invlpg.
Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Currently when x86 emulator needs to access memory, page walk is done with
broadest permission possible, so if emulated instruction was executed
by userspace process it can still access kernel memory. Fix that by
providing correct memory access to page walker during emulation.
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Cc: stable@kernel.org
Signed-off-by: Avi Kivity <avi@redhat.com>
There are two spellings of "writable" in
arch/x86/kvm/mmu.c and paging_tmpl.h .
This patch renames is_writeble_pte() to is_writable_pte()
and makes grepping easy.
New name is consistent with the definition of itself:
return pte & PT_WRITABLE_MASK;
Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Avi Kivity <avi@redhat.com>
Exit the guest pagetable walk loop if reading gpte failed. Otherwise its
possible to enter an endless loop processing the previous present pte.
Cc: stable@kernel.org
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
The invlpg prefault optimization breaks Windows 2008 R2 occasionally.
The visible effect is that the invlpg handler instantiates a pte which
is, microseconds later, written with a different gfn by another vcpu.
The OS could have other mechanisms to prevent a present translation from
being used, which the hypervisor is unaware of.
While the documentation states that the cpu is at liberty to prefetch tlb
entries, it looks like this is not heeded, so remove tlb prefetch from
invlpg.
Cc: stable@kernel.org
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Large page translations are always synchronized (either in level 3
or level 2), so its not necessary to properly deal with them
in the invlpg handler.
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
this flag notify that the host physical page we are pointing to from
the spte is write protected, and therefore we cant change its access
to be write unless we run get_user_pages(write = 1).
(this is needed for change_pte support in kvm)
Signed-off-by: Izik Eidus <ieidus@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
This patch adds support for shadow paging to the 1gb page table code in KVM.
With this code the guest can use 1gb pages even if the host does not support
them.
[ Marcelo: fix shadow page collision on pmd level if a guest 1gb page is mapped
with 4kb ptes on host level ]
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
The page walker may be used with nested paging too when accessing mmio
areas. Make it support the additional page-level too.
[ Marcelo: fix reserved bit check for 1gb pte ]
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
With the new name and the corresponding backend changes this function
can now support multiple hugepage sizes.
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
We use shadow_pte and spte inconsistently, switch to the shorter spelling.
Rename set_shadow_pte() to __set_spte() to avoid a conflict with the
existing set_spte(), and to indicate its lowlevelness.
Signed-off-by: Avi Kivity <avi@redhat.com>
Since the guest and host ptes can have wildly different format, adjust
the pte accessor names to indicate on which type of pte they operate on.
No functional changes.
Signed-off-by: Avi Kivity <avi@redhat.com>
Instead of reloading the pdptrs on every entry and exit (vmcs writes on vmx,
guest memory access on svm) extract them on demand.
Signed-off-by: Avi Kivity <avi@redhat.com>
Dixes compilation warning:
CC arch/x86/kernel/io_delay.o
arch/x86/kvm/paging_tmpl.h: In function ‘paging64_fetch’:
arch/x86/kvm/paging_tmpl.h:279: warning: ‘sptep’ may be used uninitialized in this function
arch/x86/kvm/paging_tmpl.h: In function ‘paging32_fetch’:
arch/x86/kvm/paging_tmpl.h:279: warning: ‘sptep’ may be used uninitialized in this function
warning is bogus (always have a least one level), but need to shut the compiler
up.
Signed-off-by: Jaswinder Singh Rajput <jaswinderrajput@gmail.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Detect, indicate, and propagate page faults where reserved bits are set.
Take care to handle the different paging modes, each of which has different
sets of reserved bits.
[avi: fix pte reserved bits for efer.nxe=0]
Signed-off-by: Eddie Dong <eddie.dong@intel.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
The original one is for the code before refactoring.
Signed-off-by: Yaozu (Eddie) Dong <eddie.dong@intel.com>
Signed-off-by: Sheng Yang <sheng@linux.intel.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
There is no reason to update the shadow pte here because the guest pte
is only changed to dirty state.
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
When kvm emulates an invlpg instruction, it can drop a shadow pte, but
leaves the guest tlbs intact. This can cause memory corruption when
swapping out.
Without this the other cpu can still write to a freed host physical page.
tlb smp flush must happen if rmap_remove is called always before mmu_lock
is released because the VM will take the mmu_lock before it can finally add
the page to the freelist after swapout. mmu notifier makes it safe to flush
the tlb after freeing the page (otherwise it would never be safe) so we can do
a single flush for multiple sptes invalidated.
Cc: stable@kernel.org
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
In the paging_fetch function rmap_remove is called after setting a large
pte to non-present. This causes rmap_remove to not drop the reference to
the large page. The result is a memory leak of that page.
Cc: stable@kernel.org
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Acked-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
This actually describes what is going on, rather than alerting the reader
that something strange is going on.
Signed-off-by: Avi Kivity <avi@redhat.com>
The invlpg and sync walkers lack knowledge of large host sptes,
descending to non-existant pagetable level.
Stop at directory level in such case.
Fixes SMP Windows XP with hugepages.
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
If the guest executes invlpg, peek into the pagetable and attempt to
prepopulate the shadow entry.
Also stop dirty fault updates from interfering with the fork detector.
2% improvement on RHEL3/AIM7.
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Skip syncing global pages on cr3 switch (but not on cr4/cr0). This is
important for Linux 32-bit guests with PAE, where the kmap page is
marked as global.
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
It is possible for a shadow page to have a parent link
pointing to a freed page. When zapping a high level table,
kvm_mmu_page_unlink_children fails to remove the parent_pte link.
For that to happen, the child must be unreachable via the shadow
tree, which can happen in shadow_walk_entry if the guest pte was
modified in between walk() and fetch(). Remove the parent pte
reference in such case.
Possible cause for oops in bug #2217430.
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Allow guest pagetables to go out of sync. Instead of emulating write
accesses to guest pagetables, or unshadowing them, we un-write-protect
the page table and allow the guest to modify it at will. We rely on
invlpg executions to synchronize individual ptes, and will synchronize
the entire pagetable on tlb flushes.
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
With pages out of sync invlpg needs to be trapped. For now simply nuke
the entry.
Untested on AMD.
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Examine guest pagetable and bring the shadow back in sync. Caller is responsible
for local TLB flush before re-entering guest mode.
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
It is necessary to flush all TLB's when a large spte entry is
overwritten with a normal page directory pointer.
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Convert gfn_to_pfn to use get_user_pages_fast, which can do lockless
pagetable lookups on x86. Kernel compilation on 4-way guest is 3.7%
faster on VMX.
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
EPT is 4 level by default in 32pae(48 bits), but the addr parameter
of kvm_shadow_walk->entry() only accept unsigned long as virtual
address, which is 32bit in 32pae. This result in SHADOW_PT_INDEX()
overflow when try to fetch level 4 index.
Fix it by extend kvm_shadow_walk->entry() to accept 64bit addr in
parameter.
Signed-off-by: Sheng Yang <sheng.yang@intel.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
The shadow code assigns a pte directly in one place, which is nonatomic on
i386 can can cause random memory references. Fix by using an atomic setter.
Signed-off-by: Avi Kivity <avi@qumranet.com>
Synchronize changes to host virtual addresses which are part of
a KVM memory slot to the KVM shadow mmu. This allows pte operations
like swapping, page migration, and madvise() to transparently work
with KVM.
Signed-off-by: Andrea Arcangeli <andrea@qumranet.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
This patch introduces a gfn_to_pfn() function and corresponding functions like
kvm_release_pfn_dirty(). Using these new functions, we can modify the x86
MMU to no longer assume that it can always get a struct page for any given gfn.
We don't want to eliminate gfn_to_page() entirely because a number of places
assume they can do gfn_to_page() and then kmap() the results. When we support
IO memory, gfn_to_page() will fail for IO pages although gfn_to_pfn() will
succeed.
This does not implement support for avoiding reference counting for reserved
RAM or for IO memory. However, it should make those things pretty straight
forward.
Since we're only introducing new common symbols, I don't think it will break
the non-x86 architectures but I haven't tested those. I've tested Intel,
AMD, NPT, and hugetlbfs with Windows and Linux guests.
[avi: fix overflow when shifting left pfns by adding casts]
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
Unify slots_lock acquision around vcpu_run(). This is simpler and less
error-prone.
Also fix some callsites that were not grabbing the lock properly.
[avi: drop slots_lock while in guest mode to avoid holding the lock
for indefinite periods]
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
If we populate a shadow pte due to a fault (and not speculatively due to a
pte write) then we can set the accessed bit on it, as we know it will be
set immediately on the next guest instruction. This saves a read-modify-write
operation.
Signed-off-by: Avi Kivity <avi@qumranet.com>
Create large pages mappings if the guest PTE's are marked as such and
the underlying memory is hugetlbfs backed. If the largepage contains
write-protected pages, a large pte is not used.
Gives a consistent 2% improvement for data copies on ram mounted
filesystem, without NPT/EPT.
Anthony measures a 4% improvement on 4-way kernbench, with NPT.
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
Currently an mmio guest pte is encoded in the shadow pagetable as a
not-present trapping pte, with the SHADOW_IO_MARK bit set. However
nothing is ever done with this information, so maintaining it is a
useless complication.
This patch moves the check for mmio to before shadow ptes are instantiated,
so the shadow code is never invoked for ptes that reference mmio. The code
is simpler, and with future work, can be made to handle mmio concurrently.
Signed-off-by: Avi Kivity <avi@qumranet.com>
A guest partial guest pte write will leave shadow_trap_nonpresent_pte
in spte, which generates a vmexit at the next guest access through that pte.
This patch improves this by reading the full guest pte in advance and thus
being able to update the spte and eliminate the vmexit.
This helps pae guests which use two 32-bit writes to set a single 64-bit pte.
[truncation fix by Eric]
Signed-off-by: Yaozu (Eddie) Dong <eddie.dong@intel.com>
Signed-off-by: Feng (Eric) Liu <eric.e.liu@intel.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
For improved concurrency, the guest walk is performed concurrently with other
vcpus. This means that we need to revalidate the guest ptes once we have
write-protected the guest page tables, at which point they can no longer be
modified.
The current code attempts to avoid this check if the shadow page table is not
new, on the assumption that if it has existed before, the guest could not have
modified the pte without the shadow lock. However the assumption is incorrect,
as the racing vcpu could have modified the pte, then instantiated the shadow
page, before our vcpu regains control:
vcpu0 vcpu1
fault
walk pte
modify pte
fault in same pagetable
instantiate shadow page
lookup shadow page
conclude it is old
instantiate spte based on stale guest pte
We could do something clever with generation counters, but a test run by
Marcelo suggests this is unnecessary and we can just do the revalidation
unconditionally. The pte will be in the processor cache and the check can
be quite fast.
Signed-off-by: Avi Kivity <avi@qumranet.com>
the cr3 variable is now inside the vcpu->arch structure.
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
This patch replaces the mmap_sem lock for the memory slots with a new
kvm private lock, it is needed beacuse untill now there were cases where
kvm accesses user memory while holding the mmap semaphore.
Signed-off-by: Izik Eidus <izike@qumranet.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
If some other cpu steals mmu pages between our check and an attempt to
allocate, we can run out of mmu pages. Fix by moving the check into the
same critical section as the allocation.
Signed-off-by: Avi Kivity <avi@qumranet.com>
Convert the synchronization of the shadow handling to a separate mmu_lock
spinlock.
Also guard fetch() by mmap_sem in read-mode to protect against alias
and memslot changes.
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
Since gfn_to_page() is a sleeping function, and we want to make the core mmu
spinlocked, we need to pass the page from the walker context (which can sleep)
to the shadow context (which cannot).
[marcelo: avoid recursive locking of mmap_sem]
Signed-off-by: Avi Kivity <avi@qumranet.com>
In preparation for a mmu spinlock, add kvm_read_guest_atomic()
and use it in fetch() and prefetch_page().
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
Do not hold kvm->lock mutex across the entire pagefault code,
only acquire it in places where it is necessary, such as mmu
hash list, active list, rmap and parent pte handling.
Allow concurrent guest walkers by switching walk_addr() to use
mmap_sem in read-mode.
And get rid of the lockless __gfn_to_page.
[avi: move kvm_mmu_pte_write() locking inside the function]
[avi: add locking for real mode]
[avi: fix cmpxchg locking]
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
This paves the way for multiple architecture support. Note that while
ioapic.c could potentially be shared with ia64, it is also moved.
Signed-off-by: Avi Kivity <avi@qumranet.com>
