| Message ID | 20191209200517.13382-1-sean.j.christopherson@intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: x86: Add a WARN on TIF_NEED_FPU_LOAD in kvm_load_guest_fpu() | expand |
On 09/12/19 21:05, Sean Christopherson wrote: > + /* > + * 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_arch_sched_in()) between vcpu_load() and now. via kvm_sched_in (not the arch_ function). Applied with that change. Paolo > + */ > + WARN_ON_ONCE(test_thread_flag(TIF_NEED_FPU_LOAD)); > +
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 3ed167e039e5..f2c8a053b017 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -8474,6 +8474,13 @@ 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_arch_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,
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> --- arch/x86/kvm/x86.c | 7 +++++++ 1 file changed, 7 insertions(+)