patches/kernel/0022-KVM-x86-do-not-report-preemption-if-the-steal-time-c.patch

   1 From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
   2 From: Paolo Bonzini <pbonzini@redhat.com>
   3 Date: Thu, 4 Aug 2022 15:28:32 +0200
   4 Subject: [PATCH] KVM: x86: do not report preemption if the steal time cache is
   5  stale
   6
   7 commit c3c28d24d910a746b02f496d190e0e8c6560224b upstream.
   8
   9 Commit 7e2175ebd695 ("KVM: x86: Fix recording of guest steal time
  10 / preempted status", 2021-11-11) open coded the previous call to
  11 kvm_map_gfn, but in doing so it dropped the comparison between the cached
  12 guest physical address and the one in the MSR.  This cause an incorrect
  13 cache hit if the guest modifies the steal time address while the memslots
  14 remain the same.  This can happen with kexec, in which case the preempted
  15 bit is written at the address used by the old kernel instead of
  16 the old one.
  17
  18 Cc: David Woodhouse <dwmw@amazon.co.uk>
  19 Cc: stable@vger.kernel.org
  20 Fixes: 7e2175ebd695 ("KVM: x86: Fix recording of guest steal time / preempted status")
  21 Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
  22 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  23 Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
  24 ---
  25  arch/x86/kvm/x86.c | 2 ++
  26  1 file changed, 2 insertions(+)
  27
  28 diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
  29 index 12b6dde48d03..d915dc8a964a 100644
  30 --- a/arch/x86/kvm/x86.c
  31 +++ b/arch/x86/kvm/x86.c
  32 @@ -4629,6 +4629,7 @@ static void kvm_steal_time_set_preempted(struct kvm_vcpu *vcpu)
  33         struct kvm_steal_time __user *st;
  34         struct kvm_memslots *slots;
  35         static const u8 preempted = KVM_VCPU_PREEMPTED;
  36 +       gpa_t gpa = vcpu->arch.st.msr_val & KVM_STEAL_VALID_BITS;
  37
  38         /*
  39          * The vCPU can be marked preempted if and only if the VM-Exit was on
  40 @@ -4656,6 +4657,7 @@ static void kvm_steal_time_set_preempted(struct kvm_vcpu *vcpu)
  41         slots = kvm_memslots(vcpu->kvm);
  42
  43         if (unlikely(slots->generation != ghc->generation ||
  44 +                    gpa != ghc->gpa ||
  45                      kvm_is_error_hva(ghc->hva) || !ghc->memslot))
  46                 return;
  47