On Thu, Mar 2, 2023 at 8:34 PM Mingwei Zhang <mizhang@xxxxxxxxxx> wrote:
>
> On Fri, Feb 24, 2023, Aaron Lewis wrote:
> > Check both architectural rules and KVM's own software-defined rules to
> > ensure the supported xfeatures[1] don't violate any of them.
> >
> > The architectural rules[2] and KVM's rules ensure for a given
> > feature, e.g. sse, avx, amx, etc... their associated xfeatures are
> > either all sets or none of them are set, and any dependencies
> > are enabled if needed.
> >
> > [1] EDX:EAX of CPUID.(EAX=0DH,ECX=0)
> > [2] SDM vol 1, 13.3 ENABLING THE XSAVE FEATURE SET AND XSAVE-ENABLED
> > FEATURES
> >
> > Signed-off-by: Aaron Lewis <aaronlewis@xxxxxxxxxx>
>
> Sorry, I did not get the point of this test? I run your test in an old
> (unpatched) kernel on two machines: 1) one with AMX and 2) one without
> it. (SPR and Skylake). Neither of them fails. Do you want to clarify a
> little bit?
The only known issue exists on newer versions of the kernel when run
on SPR. It occurs after the syscall, prctl (to enable XTILEDATA), was
introduced. If you run this test without the fix[1] you will get the
assert below, indicating the XTILECFG is supported by the guest, but
XTILEDATA isn't.
==== Test Assertion Failure ====
x86_64/xcr0_cpuid_test.c:116: false
pid=18124 tid=18124 errno=4 - Interrupted system call
1 0x0000000000401894: main at xcr0_cpuid_test.c:116
2 0x0000000000414263: __libc_start_call_main at libc-start.o:?
3 0x00000000004158af: __libc_start_main_impl at ??:?
4 0x0000000000401660: _start at ??:?
Failed guest assert: !__supported || __supported == ((((((1ULL))) <<
(18)) | ((((1ULL))) << (17)))) at x86_64/xcr0_cpuid_test.c:72
0x20000 0x60000 0x0
[1] KVM: x86: Clear all supported AMX xfeatures if they are not all set
https://lore.kernel.org/kvm/20230224223607.1580880-6-aaronlewis@xxxxxxxxxx/
>
>
> Thanks.
> -Mingwei
