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KVM: x86: fix presentation of TSX feature in ARCH_CAPABILITIES

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commit cbbaa2727aa3ae9e0a844803da7cef7fd3b94f2b upstream.

KVM does not implement MSR_IA32_TSX_CTRL, so it must not be presented
to the guests.  It is also confusing to have !ARCH_CAP_TSX_CTRL_MSR &&
!RTM && ARCH_CAP_TAA_NO: lack of MSR_IA32_TSX_CTRL suggests TSX was not
hidden (it actually was), yet the value says that TSX is not vulnerable
to microarchitectural data sampling.  Fix both.

Cc: stable@vger.kernel.org
Tested-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Paolo Bonzini 2019-11-18 18:58:26 +01:00 committed by Greg Kroah-Hartman
parent cc070fc5f7
commit b8911ed37d
1 changed files with 7 additions and 2 deletions
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9
arch/x86/kvm/x86.c
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@ -1024,10 +1024,15 @@ u64 kvm_get_arch_capabilities(void)
* If TSX is disabled on the system, guests are also mitigated against
* TAA and clear CPU buffer mitigation is not required for guests.
*/
if (boot_cpu_has_bug(X86_BUG_TAA) && boot_cpu_has(X86_FEATURE_RTM) &&
(data & ARCH_CAP_TSX_CTRL_MSR))
if (!boot_cpu_has(X86_FEATURE_RTM))
data &= ~ARCH_CAP_TAA_NO;
else if (!boot_cpu_has_bug(X86_BUG_TAA))
data |= ARCH_CAP_TAA_NO;
else if (data & ARCH_CAP_TSX_CTRL_MSR)
data &= ~ARCH_CAP_MDS_NO;
/* KVM does not emulate MSR_IA32_TSX_CTRL. */
data &= ~ARCH_CAP_TSX_CTRL_MSR;
return data;
}