AMD and Intel both have serializing lfence (X86_FEATURE_LFENCE_RDTSC).
They've both had it for a long time, and AMD has had it enabled in Linux
since Spectre v1 was announced.
Back then, there was a proposal to remove the serializing mfence feature
bit (X86_FEATURE_MFENCE_RDTSC), since both AMD and Intel have
serializing lfence. At the time, it was (ahem) speculated that some
hypervisors might not yet support its removal, so it remained for the
time being.
Now a year-and-a-half later, it should be safe to remove.
I asked Andrew Cooper about whether it's still needed:
So if you're virtualised, you've got no choice in the matter. lfence
is either dispatch-serialising or not on AMD, and you won't be able to
change it.
Furthermore, you can't accurately tell what state the bit is in, because
the MSR might not be virtualised at all, or may not reflect the true
state in hardware. Worse still, attempting to set the bit may not be
successful even if there isn't a fault for doing so.
Xen sets the DE_CFG bit unconditionally, as does Linux by the looks of
things (see MSR_F10H_DECFG_LFENCE_SERIALIZE_BIT). ISTR other hypervisor
vendors saying the same, but I don't have any information to hand.
If you are running under a hypervisor which has been updated, then
lfence will almost certainly be dispatch-serialising in practice, and
you'll almost certainly see the bit already set in DE_CFG. If you're
running under a hypervisor which hasn't been patched since Spectre,
you've already lost in many more ways.
I'd argue that X86_FEATURE_MFENCE_RDTSC is not worth keeping.
So remove it. This will reduce some code rot, and also make it easier
to hook barrier_nospec() up to a cmdline disable for performance
raisins, without having to need an alternative_3() macro.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/d990aa51e40063acb9888e8c1b688e41355a9588.1562255067.git.jpoimboe@redhat.com
The Hygon family 18h multi-die processor platform supports 1, 2 or
4-Dies per socket. The topology looks like this:
System View (with 1-Die 2-Socket):
|------------|
------ -----
SOCKET0 | D0 | | D1 | SOCKET1
------ -----
System View (with 2-Die 2-socket):
--------------------
| -------------|------
| | | |
------------ ------------
SOCKET0 | D1 -- D0 | | D3 -- D2 | SOCKET1
------------ ------------
System View (with 4-Die 2-Socket) :
--------------------
| -------------|------
| | | |
------------ ------------
| D1 -- D0 | | D7 -- D6 |
| | \/ | | | | \/ | |
SOCKET0 | | /\ | | | | /\ | | SOCKET1
| D2 -- D3 | | D4 -- D5 |
------------ ------------
| | | |
------|------------| |
--------------------
Currently
phys_proc_id = initial_apicid >> bits
calculates the physical processor ID from the initial_apicid by shifting
*bits*.
However, this does not work for 1-Die and 2-Die 2-socket systems.
According to document [1] section 2.1.11.1, the bits is the value of
CPUID_Fn80000008_ECX[12:15]. The possible values are 4, 5 or 6 which
mean:
4 - 1 die
5 - 2 dies
6 - 3/4 dies.
Hygon programs the initial ApicId the same way as AMD. The ApicId is
read from CPUID_Fn00000001_EBX (see section 2.1.11.1 of referrence [1])
and the definition is as below (see section 2.1.10.2.1.3 of [1]):
-------------------------------------------------
Bit | 6 | 5 4 | 3 | 2 1 0 |
|-----------|---------|--------|----------------|
IDs | Socket ID | Node ID | CCX ID | Core/Thread ID |
-------------------------------------------------
So for 3/4-Die configurations, the bits variable is 6, which is the same
as the ApicID definition field.
For 1-Die and 2-Die configurations, bits is 4 or 5, which will cause the
right shifted result to not be exactly the value of socket ID.
However, the socket ID should be obtained from ApicId[6]. To fix the
problem and match the ApicID field definition, set the shift bits to 6
for all Hygon family 18h multi-die CPUs.
Because AMD doesn't have 2-Socket systems with 1-Die/2-Die processors
(see reference [2]), this doesn't need to be changed on the AMD side but
only for Hygon.
References:
[1] https://www.amd.com/system/files/TechDocs/54945_PPR_Family_17h_Models_00h-0Fh.pdf
[2] https://www.amd.com/en/products/specifications/processors
[bp: heavily massage commit message. ]
Signed-off-by: Pu Wen <puwen@hygon.cn>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Thomas Lendacky <Thomas.Lendacky@amd.com>
Cc: Yazen Ghannam <yazen.ghannam@amd.com>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/1553355740-19999-1-git-send-email-puwen@hygon.cn
The Hygon Dhyana CPU has a topology extensions bit in CPUID. With
this bit, the kernel can get the cache information. So add support in
cpuid4_cache_lookup_regs() to get the correct cache size.
The Hygon Dhyana CPU also discovers num_cache_leaves via CPUID leaf
0x8000001d, so add support to it in find_num_cache_leaves().
Also add cacheinfo_hygon_init_llc_id() and init_hygon_cacheinfo()
functions to initialize Dhyana cache info. Setup cache cpumap in the
same way as AMD does.
Signed-off-by: Pu Wen <puwen@hygon.cn>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Cc: bp@alien8.de
Cc: tglx@linutronix.de
Cc: mingo@redhat.com
Cc: hpa@zytor.com
Cc: x86@kernel.org
Cc: thomas.lendacky@amd.com
Link: https://lkml.kernel.org/r/2a686b2ac0e2f5a1f2f5f101124d9dd44f949731.1537533369.git.puwen@hygon.cn
Add x86 architecture support for a new processor: Hygon Dhyana Family
18h. Carve out initialization code needed by Dhyana into a separate
compilation unit.
To identify Hygon Dhyana CPU, add a new vendor type X86_VENDOR_HYGON.
Since Dhyana uses AMD functionality to a large degree, select
CPU_SUP_AMD which provides that functionality.
[ bp: drop explicit license statement as it has an SPDX tag already. ]
Signed-off-by: Pu Wen <puwen@hygon.cn>
Reviewed-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: tglx@linutronix.de
Cc: mingo@redhat.com
Cc: hpa@zytor.com
Cc: x86@kernel.org
Cc: thomas.lendacky@amd.com
Link: https://lkml.kernel.org/r/1a882065223bacbde5726f3beaa70cebd8dcd814.1537533369.git.puwen@hygon.cn
