From: Sean Christopherson sean.j.christopherson@intel.com
commit c9aef3b85f425d1f6635382ec210ee5a7ef55d7d upstream.
Handle TIF_NEED_FPU_LOAD similar to how fpu__copy() handles the flag when duplicating FPU state to a new task struct. TIF_NEED_FPU_LOAD can be set any time control is transferred out of KVM, be it voluntarily, e.g. if I/O is triggered during a KVM call to get_user_pages, or involuntarily, e.g. if softirq runs after an IRQ occurs. Therefore, KVM must account for TIF_NEED_FPU_LOAD whenever it is (potentially) accessing CPU FPU state.
Fixes: 5f409e20b7945 ("x86/fpu: Defer FPU state load until return to userspace") Cc: stable@vger.kernel.org Signed-off-by: Sean Christopherson sean.j.christopherson@intel.com Signed-off-by: Paolo Bonzini pbonzini@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/x86/kvm/x86.c | 19 +++++++++++++++++-- 1 file changed, 17 insertions(+), 2 deletions(-)
--- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -8493,12 +8493,26 @@ static int complete_emulated_mmio(struct return 0; }
+static void kvm_save_current_fpu(struct fpu *fpu) +{ + /* + * If the target FPU state is not resident in the CPU registers, just + * memcpy() from current, else save CPU state directly to the target. + */ + if (test_thread_flag(TIF_NEED_FPU_LOAD)) + memcpy(&fpu->state, ¤t->thread.fpu.state, + fpu_kernel_xstate_size); + else + copy_fpregs_to_fpstate(fpu); +} + /* Swap (qemu) user FPU context for the guest FPU context. */ static void kvm_load_guest_fpu(struct kvm_vcpu *vcpu) { fpregs_lock();
- copy_fpregs_to_fpstate(vcpu->arch.user_fpu); + kvm_save_current_fpu(vcpu->arch.user_fpu); + /* PKRU is separately restored in kvm_x86_ops->run. */ __copy_kernel_to_fpregs(&vcpu->arch.guest_fpu->state, ~XFEATURE_MASK_PKRU); @@ -8514,7 +8528,8 @@ static void kvm_put_guest_fpu(struct kvm { fpregs_lock();
- copy_fpregs_to_fpstate(vcpu->arch.guest_fpu); + kvm_save_current_fpu(vcpu->arch.guest_fpu); + copy_kernel_to_fpregs(&vcpu->arch.user_fpu->state);
fpregs_mark_activate();