Commit 27f70eaa authored by Yosry Ahmed's avatar Yosry Ahmed Committed by Sean Christopherson
Browse files

KVM: SVM: Refactor SVM instruction handling on #GP intercept 



Instead of returning an opcode from svm_instr_opcode() and then passing
it to emulate_svm_instr(), which uses it to find the corresponding exit
code and intercept handler, return the exit code directly from
svm_instr_opcode(), and rename it to svm_get_decoded_instr_exit_code().

emulate_svm_instr() boils down to synthesizing a #VMEXIT or calling the
intercept handler, so open-code it in gp_interception(), and use
svm_invoke_exit_handler() to call the intercept handler based on
the exit code. This allows for dropping the SVM_INSTR_* enum, and the
const array mapping its values to exit codes and intercept handlers.

In gp_intercept(), handle SVM instructions and first with an early return,
and invert is_guest_mode() checks, un-indenting the rest of the code.

No functional change intended.

Signed-off-by: default avatarYosry Ahmed <yosry@kernel.org>
Link: https://patch.msgid.link/20260316202732.3164936-3-yosry@kernel.org


[sean: add BUILD_BUG_ON(), tweak formatting/naming]
Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
parent c85aaff2

arch/x86/kvm/svm/svm.c

+26 −51
Original line number Diff line number Diff line
@@ -2236,54 +2236,28 @@ static int vmrun_interception(struct kvm_vcpu *vcpu) 
	return nested_svm_vmrun(vcpu);

}



enum {

	NONE_SVM_INSTR,

	SVM_INSTR_VMRUN,

	SVM_INSTR_VMLOAD,

	SVM_INSTR_VMSAVE,

};



/* Return NONE_SVM_INSTR if not SVM instrs, otherwise return decode result */

static int svm_instr_opcode(struct kvm_vcpu *vcpu)

/* Return 0 if not SVM instr, otherwise return associated exit_code */

static u64 svm_get_decoded_instr_exit_code(struct kvm_vcpu *vcpu)

{

	struct x86_emulate_ctxt *ctxt = vcpu->arch.emulate_ctxt;



	if (ctxt->b != 0x1 || ctxt->opcode_len != 2)

		return NONE_SVM_INSTR;

		return 0;



	BUILD_BUG_ON(!SVM_EXIT_VMRUN || !SVM_EXIT_VMLOAD || !SVM_EXIT_VMSAVE);



	switch (ctxt->modrm) {

	case 0xd8: /* VMRUN */

		return SVM_INSTR_VMRUN;

		return SVM_EXIT_VMRUN;

	case 0xda: /* VMLOAD */

		return SVM_INSTR_VMLOAD;

		return SVM_EXIT_VMLOAD;

	case 0xdb: /* VMSAVE */

		return SVM_INSTR_VMSAVE;

		return SVM_EXIT_VMSAVE;

	default:

		break;

	}



	return NONE_SVM_INSTR;

}



static int emulate_svm_instr(struct kvm_vcpu *vcpu, int opcode)

{

	const int guest_mode_exit_codes[] = {

		[SVM_INSTR_VMRUN] = SVM_EXIT_VMRUN,

		[SVM_INSTR_VMLOAD] = SVM_EXIT_VMLOAD,

		[SVM_INSTR_VMSAVE] = SVM_EXIT_VMSAVE,

	};

	int (*const svm_instr_handlers[])(struct kvm_vcpu *vcpu) = {

		[SVM_INSTR_VMRUN] = vmrun_interception,

		[SVM_INSTR_VMLOAD] = vmload_interception,

		[SVM_INSTR_VMSAVE] = vmsave_interception,

	};

	struct vcpu_svm *svm = to_svm(vcpu);



	if (is_guest_mode(vcpu)) {

		nested_svm_simple_vmexit(svm, guest_mode_exit_codes[opcode]);

		return 1;

	}

	return svm_instr_handlers[opcode](vcpu);

	return 0;

}



/*
@@ -2298,7 +2272,7 @@ static int gp_interception(struct kvm_vcpu *vcpu) 
{

	struct vcpu_svm *svm = to_svm(vcpu);

	u32 error_code = svm->vmcb->control.exit_info_1;

	int opcode;

	u64 svm_exit_code;



	/* Both #GP cases have zero error_code */

	if (error_code)
@@ -2308,26 +2282,27 @@ static int gp_interception(struct kvm_vcpu *vcpu) 
	if (x86_decode_emulated_instruction(vcpu, 0, NULL, 0) != EMULATION_OK)

		goto reinject;



	opcode = svm_instr_opcode(vcpu);



	if (opcode == NONE_SVM_INSTR) {

		if (!enable_vmware_backdoor)

	svm_exit_code = svm_get_decoded_instr_exit_code(vcpu);

	if (svm_exit_code) {

		/* All SVM instructions expect page aligned RAX */

		if (svm->vmcb->save.rax & ~PAGE_MASK)

			goto reinject;



		if (!is_guest_mode(vcpu))

			return svm_invoke_exit_handler(vcpu, svm_exit_code);



		nested_svm_simple_vmexit(svm, svm_exit_code);

		return 1;

	}



	/*

	 * VMware backdoor emulation on #GP interception only handles

		 * IN{S}, OUT{S}, and RDPMC.

	 * IN{S}, OUT{S}, and RDPMC, and only for L1.

	 */

		if (!is_guest_mode(vcpu))

			return kvm_emulate_instruction(vcpu,

				EMULTYPE_VMWARE_GP | EMULTYPE_NO_DECODE);

	} else {

		/* All SVM instructions expect page aligned RAX */

		if (svm->vmcb->save.rax & ~PAGE_MASK)

	if (!enable_vmware_backdoor || is_guest_mode(vcpu))

		goto reinject;



		return emulate_svm_instr(vcpu, opcode);

	}

	return kvm_emulate_instruction(vcpu, EMULTYPE_VMWARE_GP | EMULTYPE_NO_DECODE);



reinject:

	kvm_queue_exception_e(vcpu, GP_VECTOR, error_code);