diff options
| author | Sean Christopherson <sean.j.christopherson@intel.com> | 2019-12-09 12:05:17 -0800 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2020-01-08 18:16:02 +0100 |
| commit | 95145c25a78cc0a9d3cbc75708abde432310c5a1 (patch) | |
| tree | 5bdfd34337bfb6a0ef955f78d8d667cead2d4061 | |
| parent | f958bd2314d117f8c29f4821401bc1925bc2e5ef (diff) | |
KVM: x86: Add a WARN on TIF_NEED_FPU_LOAD in kvm_load_guest_fpu()
WARN once in kvm_load_guest_fpu() if TIF_NEED_FPU_LOAD is observed, as
that would mean that KVM is corrupting userspace's FPU by saving
unknown register state into arch.user_fpu. Add a comment to explain
why KVM WARNs on TIF_NEED_FPU_LOAD instead of implementing logic
similar to fpu__copy().
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
| -rw-r--r-- | arch/x86/kvm/x86.c | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 0af5cb637bea..25aac4c81b12 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -8476,6 +8476,13 @@ static void kvm_load_guest_fpu(struct kvm_vcpu *vcpu) { fpregs_lock(); + /* + * Reloading userspace's FPU is handled by kvm_arch_vcpu_load(), both + * for direct calls from userspace (via vcpu_load()) and if this task + * is preempted (via kvm_sched_in()) between vcpu_load() and now. + */ + WARN_ON_ONCE(test_thread_flag(TIF_NEED_FPU_LOAD)); + copy_fpregs_to_fpstate(vcpu->arch.user_fpu); /* PKRU is separately restored in kvm_x86_ops->run. */ __copy_kernel_to_fpregs(&vcpu->arch.guest_fpu->state, |