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Commit 6a10f818 authored by Paolo Bonzini's avatar Paolo Bonzini Committed by Greg Kroah-Hartman
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KVM: x86: fix presentation of TSX feature in ARCH_CAPABILITIES 



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: default avatarJim Mattson <jmattson@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 5efbd9a9

arch/x86/kvm/x86.c

+7 −2
Original line number Diff line number Diff line
@@ -1174,10 +1174,15 @@ 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;

}