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    SubjectRe: [PATCH AUTOSEL for 4.14 12/67] KVM: x86: add support for emulating UMIP
    Date
    On Thu, Mar 08, 2018 at 01:46:39AM -0500, Paolo Bonzini wrote:
    >
    >
    >----- Original Message -----
    >> From: "Sasha Levin" <Alexander.Levin@microsoft.com>
    >> To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
    >> Cc: "Paolo Bonzini" <pbonzini@redhat.com>, "Sasha Levin" <Alexander.Levin@microsoft.com>
    >> Sent: Thursday, March 8, 2018 5:57:36 AM
    >> Subject: [PATCH AUTOSEL for 4.14 12/67] KVM: x86: add support for emulating UMIP
    >>
    >> From: Paolo Bonzini <pbonzini@redhat.com>
    >>
    >> [ Upstream commit 66336cab3531d3325ebde36a04725dddd0c42cb5 ]
    >>
    >> The User-Mode Instruction Prevention feature present in recent Intel
    >> processor prevents a group of instructions (sgdt, sidt, sldt, smsw, and
    >> str) from being executed with CPL > 0. Otherwise, a general protection
    >> fault is issued.
    >>
    >> UMIP instructions in general are also able to trigger vmexits, so we can
    >> actually emulate UMIP on older processors. This commit sets up the
    >> infrastructure so that kvm-intel.ko and kvm-amd.ko can set the UMIP
    >> feature bit for CPUID even if the feature is not actually available
    >> in hardware.
    >>
    >> Reviewed-by: Wanpeng Li <wanpeng.li@hotmail.com>
    >> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
    >> Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
    >
    >This is not enough (there were a couple bugs, plus you have not
    >added the changes needed to the handle SLDT, STR, etc. in the
    >emulator). But since this is a feature, why is it being backported
    >to 4.14, especially without any testing??

    Hi Paolo,

    They were proposed for stable as part of the automatic patch selection
    process. I'll drop this patch.

    --

    Thanks,
    Sasha
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