Commit 00682995 authored by Sean Christopherson's avatar Sean Christopherson
Browse files

KVM: SVM: Treat all "skip" emulation for SEV guests as outright failures 

Treat EMULTYPE_SKIP failures on SEV guests as unhandleable emulation
instead of simply resuming the guest, and drop the hack-a-fix which
effects that behavior for the INT3/INTO injection path.  If KVM can't
skip an instruction for which KVM has already done partial emulation,
resuming the guest is undesirable as doing so may corrupt guest state.

Link: https://lore.kernel.org/r/20230825013621.2845700-5-seanjc@google.com


Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
parent aeb904f6

arch/x86/kvm/svm/svm.c

+1 −11
Original line number Diff line number Diff line
@@ -364,8 +364,6 @@ static void svm_set_interrupt_shadow(struct kvm_vcpu *vcpu, int mask) 
		svm->vmcb->control.int_state |= SVM_INTERRUPT_SHADOW_MASK;



}

static int svm_check_emulate_instruction(struct kvm_vcpu *vcpu, int emul_type,

					 void *insn, int insn_len);



static int __svm_skip_emulated_instruction(struct kvm_vcpu *vcpu,

					   bool commit_side_effects)
@@ -386,14 +384,6 @@ static int __svm_skip_emulated_instruction(struct kvm_vcpu *vcpu, 
	}



	if (!svm->next_rip) {

		/*

		 * FIXME: Drop this when kvm_emulate_instruction() does the

		 * right thing and treats "can't emulate" as outright failure

		 * for EMULTYPE_SKIP.

		 */

		if (svm_check_emulate_instruction(vcpu, EMULTYPE_SKIP, NULL, 0) != X86EMUL_CONTINUE)

			return 0;



		if (unlikely(!commit_side_effects))

			old_rflags = svm->vmcb->save.rflags;
@@ -4781,7 +4771,7 @@ static int svm_check_emulate_instruction(struct kvm_vcpu *vcpu, int emul_type, 
	 */

	if (unlikely(!insn)) {

		if (emul_type & EMULTYPE_SKIP)

			return X86EMUL_RETRY_INSTR;

			return X86EMUL_UNHANDLEABLE;



		kvm_queue_exception(vcpu, UD_VECTOR);

		return X86EMUL_PROPAGATE_FAULT;

arch/x86/kvm/x86.c

+7 −2
Original line number Diff line number Diff line
@@ -8874,9 +8874,14 @@ int x86_emulate_instruction(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa, 
	bool writeback = true;



	r = kvm_check_emulate_insn(vcpu, emulation_type, insn, insn_len);

	if (r != X86EMUL_CONTINUE)

	if (r != X86EMUL_CONTINUE) {

		if (r == X86EMUL_RETRY_INSTR || r == X86EMUL_PROPAGATE_FAULT)

			return 1;



		WARN_ON_ONCE(r != X86EMUL_UNHANDLEABLE);

		return handle_emulation_failure(vcpu, emulation_type);

	}



	vcpu->arch.l1tf_flush_l1d = true;



	if (!(emulation_type & EMULTYPE_NO_DECODE)) {