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    Subject[PATCH 4.4 065/162] KVM: x86: fix presentation of TSX feature in ARCH_CAPABILITIES
    Date
    From: Paolo Bonzini <pbonzini@redhat.com>

    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>

    ---
    arch/x86/kvm/x86.c | 9 +++++++--
    1 file changed, 7 insertions(+), 2 deletions(-)

    --- a/arch/x86/kvm/x86.c
    +++ b/arch/x86/kvm/x86.c
    @@ -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;
    }


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