Commit aeb904f6 authored by Sean Christopherson's avatar Sean Christopherson
Browse files

KVM: x86: Refactor can_emulate_instruction() return to be more expressive 

Refactor and rename can_emulate_instruction() to allow vendor code to
return more than true/false, e.g. to explicitly differentiate between
"retry", "fault", and "unhandleable".  For now, just do the plumbing, a
future patch will expand SVM's implementation to signal outright failure
if KVM attempts EMULTYPE_SKIP on an SEV guest.

No functional change intended (or rather, none that are visible to the
guest or userspace).

Link: https://lore.kernel.org/r/20230825013621.2845700-4-seanjc@google.com


Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
parent bc3d7c55

arch/x86/include/asm/kvm-x86-ops.h

+1 −1
Original line number Diff line number Diff line
@@ -126,7 +126,7 @@ KVM_X86_OP_OPTIONAL(vm_copy_enc_context_from) 
KVM_X86_OP_OPTIONAL(vm_move_enc_context_from)

KVM_X86_OP_OPTIONAL(guest_memory_reclaimed)

KVM_X86_OP(get_msr_feature)

KVM_X86_OP(can_emulate_instruction)

KVM_X86_OP(check_emulate_instruction)

KVM_X86_OP(apic_init_signal_blocked)

KVM_X86_OP_OPTIONAL(enable_l2_tlb_flush)

KVM_X86_OP_OPTIONAL(migrate_timers)

arch/x86/include/asm/kvm_host.h

+2 −2
Original line number Diff line number Diff line
@@ -1734,7 +1734,7 @@ struct kvm_x86_ops { 


	int (*get_msr_feature)(struct kvm_msr_entry *entry);



	bool (*can_emulate_instruction)(struct kvm_vcpu *vcpu, int emul_type,

	int (*check_emulate_instruction)(struct kvm_vcpu *vcpu, int emul_type,

					 void *insn, int insn_len);



	bool (*apic_init_signal_blocked)(struct kvm_vcpu *vcpu);

arch/x86/kvm/svm/svm.c

+17 −14
Original line number Diff line number Diff line
@@ -364,7 +364,7 @@ static void svm_set_interrupt_shadow(struct kvm_vcpu *vcpu, int mask) 
		svm->vmcb->control.int_state |= SVM_INTERRUPT_SHADOW_MASK;



}

static bool svm_can_emulate_instruction(struct kvm_vcpu *vcpu, int emul_type,

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,
@@ -391,7 +391,7 @@ static int __svm_skip_emulated_instruction(struct kvm_vcpu *vcpu, 
		 * right thing and treats "can't emulate" as outright failure

		 * for EMULTYPE_SKIP.

		 */

		if (!svm_can_emulate_instruction(vcpu, EMULTYPE_SKIP, NULL, 0))

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

			return 0;



		if (unlikely(!commit_side_effects))
@@ -4727,7 +4727,7 @@ static void svm_enable_smi_window(struct kvm_vcpu *vcpu) 
}

#endif



static bool svm_can_emulate_instruction(struct kvm_vcpu *vcpu, int emul_type,

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

					 void *insn, int insn_len)

{

	bool smep, smap, is_user;
@@ -4735,7 +4735,7 @@ static bool svm_can_emulate_instruction(struct kvm_vcpu *vcpu, int emul_type, 


	/* Emulation is always possible when KVM has access to all guest state. */

	if (!sev_guest(vcpu->kvm))

		return true;

		return X86EMUL_CONTINUE;



	/* #UD and #GP should never be intercepted for SEV guests. */

	WARN_ON_ONCE(emul_type & (EMULTYPE_TRAP_UD |
@@ -4747,14 +4747,14 @@ static bool svm_can_emulate_instruction(struct kvm_vcpu *vcpu, int emul_type, 
	 * to guest register state.

	 */

	if (sev_es_guest(vcpu->kvm))

		return false;

		return X86EMUL_RETRY_INSTR;



	/*

	 * Emulation is possible if the instruction is already decoded, e.g.

	 * when completing I/O after returning from userspace.

	 */

	if (emul_type & EMULTYPE_NO_DECODE)

		return true;

		return X86EMUL_CONTINUE;



	/*

	 * Emulation is possible for SEV guests if and only if a prefilled
@@ -4780,9 +4780,11 @@ static bool svm_can_emulate_instruction(struct kvm_vcpu *vcpu, int emul_type, 
	 * success (and in practice it will work the vast majority of the time).

	 */

	if (unlikely(!insn)) {

		if (!(emul_type & EMULTYPE_SKIP))

		if (emul_type & EMULTYPE_SKIP)

			return X86EMUL_RETRY_INSTR;



		kvm_queue_exception(vcpu, UD_VECTOR);

		return false;

		return X86EMUL_PROPAGATE_FAULT;

	}



	/*
@@ -4793,7 +4795,7 @@ static bool svm_can_emulate_instruction(struct kvm_vcpu *vcpu, int emul_type, 
	 * table used to translate CS:RIP resides in emulated MMIO.

	 */

	if (likely(insn_len))

		return true;

		return X86EMUL_CONTINUE;



	/*

	 * Detect and workaround Errata 1096 Fam_17h_00_0Fh.
@@ -4851,6 +4853,7 @@ static bool svm_can_emulate_instruction(struct kvm_vcpu *vcpu, int emul_type, 
			kvm_inject_gp(vcpu, 0);

		else

			kvm_make_request(KVM_REQ_TRIPLE_FAULT, vcpu);

		return X86EMUL_PROPAGATE_FAULT;

	}



resume_guest:
@@ -4868,7 +4871,7 @@ static bool svm_can_emulate_instruction(struct kvm_vcpu *vcpu, int emul_type, 
	 * doesn't explicitly define "ignored", i.e. doing nothing and letting

	 * the guest spin is technically "ignoring" the access.

	 */

	return false;

	return X86EMUL_RETRY_INSTR;

}



static bool svm_apic_init_signal_blocked(struct kvm_vcpu *vcpu)
@@ -5028,7 +5031,7 @@ static struct kvm_x86_ops svm_x86_ops __initdata = { 
	.vm_copy_enc_context_from = sev_vm_copy_enc_context_from,

	.vm_move_enc_context_from = sev_vm_move_enc_context_from,



	.can_emulate_instruction = svm_can_emulate_instruction,

	.check_emulate_instruction = svm_check_emulate_instruction,



	.apic_init_signal_blocked = svm_apic_init_signal_blocked,

arch/x86/kvm/vmx/vmx.c

+6 −6
Original line number Diff line number Diff line
@@ -1657,7 +1657,7 @@ static int vmx_rtit_ctl_check(struct kvm_vcpu *vcpu, u64 data) 
	return 0;

}



static bool vmx_can_emulate_instruction(struct kvm_vcpu *vcpu, int emul_type,

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

					 void *insn, int insn_len)

{

	/*
@@ -1669,9 +1669,9 @@ static bool vmx_can_emulate_instruction(struct kvm_vcpu *vcpu, int emul_type, 
	 */

	if (to_vmx(vcpu)->exit_reason.enclave_mode) {

		kvm_queue_exception(vcpu, UD_VECTOR);

		return false;

		return X86EMUL_PROPAGATE_FAULT;

	}

	return true;

	return X86EMUL_CONTINUE;

}



static int skip_emulated_instruction(struct kvm_vcpu *vcpu)
@@ -5792,7 +5792,7 @@ static int handle_ept_misconfig(struct kvm_vcpu *vcpu) 
{

	gpa_t gpa;



	if (!vmx_can_emulate_instruction(vcpu, EMULTYPE_PF, NULL, 0))

	if (vmx_check_emulate_instruction(vcpu, EMULTYPE_PF, NULL, 0))

		return 1;



	/*
@@ -8341,7 +8341,7 @@ static struct kvm_x86_ops vmx_x86_ops __initdata = { 
	.enable_smi_window = vmx_enable_smi_window,

#endif



	.can_emulate_instruction = vmx_can_emulate_instruction,

	.check_emulate_instruction = vmx_check_emulate_instruction,

	.apic_init_signal_blocked = vmx_apic_init_signal_blocked,

	.migrate_timers = vmx_migrate_timers,

arch/x86/kvm/x86.c

+9 −6
Original line number Diff line number Diff line
@@ -7474,10 +7474,10 @@ int kvm_write_guest_virt_system(struct kvm_vcpu *vcpu, gva_t addr, void *val, 
}

EXPORT_SYMBOL_GPL(kvm_write_guest_virt_system);



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

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

				  void *insn, int insn_len)

{

	return static_call(kvm_x86_can_emulate_instruction)(vcpu, emul_type,

	return static_call(kvm_x86_check_emulate_instruction)(vcpu, emul_type,

							      insn, insn_len);

}
@@ -7488,8 +7488,10 @@ int handle_ud(struct kvm_vcpu *vcpu) 
	int emul_type = EMULTYPE_TRAP_UD;

	char sig[5]; /* ud2; .ascii "kvm" */

	struct x86_exception e;

	int r;



	if (unlikely(!kvm_can_emulate_insn(vcpu, emul_type, NULL, 0)))

	r = kvm_check_emulate_insn(vcpu, emul_type, NULL, 0);

	if (r != X86EMUL_CONTINUE)

		return 1;



	if (fep_flags &&
@@ -8871,7 +8873,8 @@ int x86_emulate_instruction(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa, 
	struct x86_emulate_ctxt *ctxt = vcpu->arch.emulate_ctxt;

	bool writeback = true;



	if (unlikely(!kvm_can_emulate_insn(vcpu, emulation_type, insn, insn_len)))

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

	if (r != X86EMUL_CONTINUE)

		return 1;



	vcpu->arch.l1tf_flush_l1d = true;