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authorWanpeng Li <wanpengli@tencent.com>2019-07-22 07:26:20 +0300
committerPaolo Bonzini <pbonzini@redhat.com>2019-07-22 14:55:47 +0300
commite751732486eb3f159089a64d1901992b1357e7cc (patch)
treedcb8475c68ea9480fa76872b6c0ad07bd854b621 /arch
parentec269475cba7bcdd1eb8fdf8e87f4c6c81a376fe (diff)
downloadlinux-e751732486eb3f159089a64d1901992b1357e7cc.tar.xz
KVM: X86: Fix fpu state crash in kvm guest
The idea before commit 240c35a37 (which has just been reverted) was that we have the following FPU states: userspace (QEMU) guest --------------------------------------------------------------------------- processor vcpu->arch.guest_fpu >>> KVM_RUN: kvm_load_guest_fpu vcpu->arch.user_fpu processor >>> preempt out vcpu->arch.user_fpu current->thread.fpu >>> preempt in vcpu->arch.user_fpu processor >>> back to userspace >>> kvm_put_guest_fpu processor vcpu->arch.guest_fpu --------------------------------------------------------------------------- With the new lazy model we want to get the state back to the processor when schedule in from current->thread.fpu. Reported-by: Thomas Lambertz <mail@thomaslambertz.de> Reported-by: anthony <antdev66@gmail.com> Tested-by: anthony <antdev66@gmail.com> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Radim Krčmář <rkrcmar@redhat.com> Cc: Thomas Lambertz <mail@thomaslambertz.de> Cc: anthony <antdev66@gmail.com> Cc: stable@vger.kernel.org Fixes: 5f409e20b (x86/fpu: Defer FPU state load until return to userspace) Signed-off-by: Wanpeng Li <wanpengli@tencent.com> [Add a comment in front of the warning. - Paolo] Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/kvm/x86.c9
1 files changed, 6 insertions, 3 deletions
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index cf2afdf8facf..7eb56f8e2ea8 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3306,6 +3306,10 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
kvm_x86_ops->vcpu_load(vcpu, cpu);
+ fpregs_assert_state_consistent();
+ if (test_thread_flag(TIF_NEED_FPU_LOAD))
+ switch_fpu_return();
+
/* Apply any externally detected TSC adjustments (due to suspend) */
if (unlikely(vcpu->arch.tsc_offset_adjustment)) {
adjust_tsc_offset_host(vcpu, vcpu->arch.tsc_offset_adjustment);
@@ -7990,9 +7994,8 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
trace_kvm_entry(vcpu->vcpu_id);
guest_enter_irqoff();
- fpregs_assert_state_consistent();
- if (test_thread_flag(TIF_NEED_FPU_LOAD))
- switch_fpu_return();
+ /* The preempt notifier should have taken care of the FPU already. */
+ WARN_ON_ONCE(test_thread_flag(TIF_NEED_FPU_LOAD));
if (unlikely(vcpu->arch.switch_db_regs)) {
set_debugreg(0, 7);