lkml.org 
[lkml]   [2021]   [May]   [31]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 5.10 057/252] KVM: X86: Fix vCPU preempted state from guests point of view
    Date
    From: Wanpeng Li <wanpengli@tencent.com>

    commit 1eff0ada88b48e4ac1e3fe26483b3684fedecd27 upstream.

    Commit 66570e966dd9 (kvm: x86: only provide PV features if enabled in guest's
    CPUID) avoids to access pv tlb shootdown host side logic when this pv feature
    is not exposed to guest, however, kvm_steal_time.preempted not only leveraged
    by pv tlb shootdown logic but also mitigate the lock holder preemption issue.
    >From guest's point of view, vCPU is always preempted since we lose the reset
    of kvm_steal_time.preempted before vmentry if pv tlb shootdown feature is not
    exposed. This patch fixes it by clearing kvm_steal_time.preempted before
    vmentry.

    Fixes: 66570e966dd9 (kvm: x86: only provide PV features if enabled in guest's CPUID)
    Reviewed-by: Sean Christopherson <seanjc@google.com>
    Cc: stable@vger.kernel.org
    Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
    Message-Id: <1621339235-11131-3-git-send-email-wanpengli@tencent.com>
    Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    arch/x86/kvm/x86.c | 2 ++
    1 file changed, 2 insertions(+)

    --- a/arch/x86/kvm/x86.c
    +++ b/arch/x86/kvm/x86.c
    @@ -3006,6 +3006,8 @@ static void record_steal_time(struct kvm
    st->preempted & KVM_VCPU_FLUSH_TLB);
    if (xchg(&st->preempted, 0) & KVM_VCPU_FLUSH_TLB)
    kvm_vcpu_flush_tlb_guest(vcpu);
    + } else {
    + st->preempted = 0;
    }

    vcpu->arch.st.preempted = 0;

    \
     
     \ /
      Last update: 2021-05-31 16:24    [W:2.776 / U:0.224 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site