KVM: x86: Handle TIF_NEED_FPU_LOAD in kvm_{load,put}_guest_fpu() (c9aef3b8) · Commits · 戴 / test

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: ("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>

arch/x86/kvm/x86.c

+17 −2

Original line number	Diff line number	Diff line
		@@ -8558,12 +8558,26 @@ static int complete_emulated_mmio(struct kvm_vcpu *vcpu)
		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, &current->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);
		@@ -8579,7 +8593,8 @@ static void kvm_put_guest_fpu(struct kvm_vcpu *vcpu)
		{
		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();

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