releases/3.10.34/kvm-svm-fix-cr8-intercept-window.patch

   1 From 596f3142d2b7be307a1652d59e7b93adab918437 Mon Sep 17 00:00:00 2001
   2 From: Radim Krčmář <rkrcmar@redhat.com>
   3 Date: Tue, 11 Mar 2014 19:11:18 +0100
   4 Subject: KVM: SVM: fix cr8 intercept window
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   8
   9 From: Radim Krčmář <rkrcmar@redhat.com>
  10
  11 commit 596f3142d2b7be307a1652d59e7b93adab918437 upstream.
  12
  13 We always disable cr8 intercept in its handler, but only re-enable it
  14 if handling KVM_REQ_EVENT, so there can be a window where we do not
  15 intercept cr8 writes, which allows an interrupt to disrupt a higher
  16 priority task.
  17
  18 Fix this by disabling intercepts in the same function that re-enables
  19 them when needed. This fixes BSOD in Windows 2008.
  20
  21 Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
  22 Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
  23 Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
  24 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  25
  26 ---
  27  arch/x86/kvm/svm.c |    6 +++---
  28  1 file changed, 3 insertions(+), 3 deletions(-)
  29
  30 --- a/arch/x86/kvm/svm.c
  31 +++ b/arch/x86/kvm/svm.c
  32 @@ -2985,10 +2985,8 @@ static int cr8_write_interception(struct
  33         u8 cr8_prev = kvm_get_cr8(&svm->vcpu);
  34         /* instruction emulation calls kvm_set_cr8() */
  35         r = cr_interception(svm);
  36 -       if (irqchip_in_kernel(svm->vcpu.kvm)) {
  37 -               clr_cr_intercept(svm, INTERCEPT_CR8_WRITE);
  38 +       if (irqchip_in_kernel(svm->vcpu.kvm))
  39                 return r;
  40 -       }
  41         if (cr8_prev <= kvm_get_cr8(&svm->vcpu))
  42                 return r;
  43         kvm_run->exit_reason = KVM_EXIT_SET_TPR;
  44 @@ -3550,6 +3548,8 @@ static void update_cr8_intercept(struct
  45         if (is_guest_mode(vcpu) && (vcpu->arch.hflags & HF_VINTR_MASK))
  46                 return;
  47
  48 +       clr_cr_intercept(svm, INTERCEPT_CR8_WRITE);
  49 +
  50         if (irr == -1)
  51                 return;
  52