The Linux Kernel contains some inline assembly source code which has
wrong asm register constraints in arch/ia64/kvm/vtlb.c.
I observed this on Kernel 3.2.35 but it is also true on the most
recent Kernel 3.9-rc1.
File arch/ia64/kvm/vtlb.c:
u64 guest_vhpt_lookup(u64 iha, u64 *pte)
{
u64 ret;
struct thash_data *data;
data = __vtr_lookup(current_vcpu, iha, D_TLB);
if (data != NULL)
thash_vhpt_insert(current_vcpu, data->page_flags,
data->itir, iha, D_TLB);
asm volatile (
"rsm psr.ic|psr.i;;"
"srlz.d;;"
"ld8.s r9=[%1];;"
"tnat.nz p6,p7=r9;;"
"(p6) mov %0=1;"
"(p6) mov r9=r0;"
"(p7) extr.u r9=r9,0,53;;"
"(p7) mov %0=r0;"
"(p7) st8 [%2]=r9;;"
"ssm psr.ic;;"
"srlz.d;;"
"ssm psr.i;;"
"srlz.d;;"
: "=r"(ret) : "r"(iha), "r"(pte):"memory");
return ret;
}
The list of output registers is
: "=r"(ret) : "r"(iha), "r"(pte):"memory");
The constraint "=r" means that the GCC has to maintain that these vars
are in registers and contain valid info when the program flow leaves
the assembly block (output registers).
But "=r" also means that GCC can put them in registers that are used
as input registers. Input registers are iha, pte on the example.
If the predicate p7 is true, the 8th assembly instruction
"(p7) mov %0=r0;"
is the first one which writes to a register which is maintained by the
register constraints; it sets %0. %0 means the first register operand;
it is ret here.
This instruction might overwrite the %2 register (pte) which is needed
by the next instruction:
"(p7) st8 [%2]=r9;;"
Whether it really happens depends on how GCC decides what registers it
uses and how it optimizes the code.
The attached patch fixes the register operand constraints in
arch/ia64/kvm/vtlb.c.
The register constraints should be
: "=&r"(ret) : "r"(iha), "r"(pte):"memory");
The & means that GCC must not use any of the input registers to place
this output register in.
This is Debian bug#702639
(http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=702639).
The patch is applicable on Kernel 3.9-rc1, 3.2.35 and many other versions.
Signed-off-by: Stephan Schreiber <info@fs-driver.org>
Cc: stable@vger.kernel.org
Signed-off-by: Tony Luck <tony.luck@intel.com>
Len Brown pointed out that allmodconfig is broken for
ia64 because of:
arch/ia64/kvm/vmm.c: In function 'vmm_spin_unlock':
arch/ia64/kvm/vmm.c:70: error: 'spinlock_t' has no member named 'raw_lock'
KVM has it's own spinlock routines. It should not depend on the base kernel
spinlock_t type (which changed when ia64 switched to ticket locks). Define
its own vmm_spinlock_t type.
Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Currently, the interrupt enable bit is cleared when in
the vmm. This patch sets the bit and the external interrupts can
be dealt with when in the vmm. This improves the I/O performance.
Signed-off-by: Yang Zhang <yang.zhang@intel.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
define paravirt_dv_serialize_data() and insert it to suppress
false positive warnings.
Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Simply the logic of hash vTLB, and export kvm_gpa_to_mpa.
Signed-off-by: Xiantao Zhang <xiantao.zhang@intel.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Remove some unnecessary blank lines to accord with Kernel's coding style.
Also remove vcpu_get_itir_on_fault due to no reference to it.
Signed-off-by: Xiantao Zhang <xiantao.zhang@intel.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Using vt-d, kvm guests can be assigned physcial devices, so
this patch introduce a new mmio type (directed mmio)
to handle its mmio access.
Signed-off-by: Xiantao Zhang <xiantao.zhang@intel.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
