Commit f8ea7c60 authored by Vitaly Kuznetsov's avatar Vitaly Kuznetsov Committed by Paolo Bonzini
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x86: kvm: svm: propagate errors from skip_emulated_instruction() 



On AMD, kvm_x86_ops->skip_emulated_instruction(vcpu) can, in theory,
fail: in !nrips case we call kvm_emulate_instruction(EMULTYPE_SKIP).
Currently, we only do printk(KERN_DEBUG) when this happens and this
is not ideal. Propagate the error up the stack.

On VMX, skip_emulated_instruction() doesn't fail, we have two call
sites calling it explicitly: handle_exception_nmi() and
handle_task_switch(), we can just ignore the result.

On SVM, we also have two explicit call sites:
svm_queue_exception() and it seems we don't need to do anything there as
we check if RIP was advanced or not. In task_switch_interception(),
however, we are better off not proceeding to kvm_task_switch() in case
skip_emulated_instruction() failed.

Suggested-by: default avatarSean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: default avatarVitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 05402f64

arch/x86/include/asm/kvm_host.h

+1 −1
Original line number Diff line number Diff line
@@ -1070,7 +1070,7 @@ struct kvm_x86_ops { 


	void (*run)(struct kvm_vcpu *vcpu);

	int (*handle_exit)(struct kvm_vcpu *vcpu);

	void (*skip_emulated_instruction)(struct kvm_vcpu *vcpu);

	int (*skip_emulated_instruction)(struct kvm_vcpu *vcpu);

	void (*set_interrupt_shadow)(struct kvm_vcpu *vcpu, int mask);

	u32 (*get_interrupt_shadow)(struct kvm_vcpu *vcpu);

	void (*patch_hypercall)(struct kvm_vcpu *vcpu,

arch/x86/kvm/svm.c

+20 −16
Original line number Diff line number Diff line
@@ -768,7 +768,7 @@ static void svm_set_interrupt_shadow(struct kvm_vcpu *vcpu, int mask) 


}



static void skip_emulated_instruction(struct kvm_vcpu *vcpu)

static int skip_emulated_instruction(struct kvm_vcpu *vcpu)

{

	struct vcpu_svm *svm = to_svm(vcpu);
@@ -777,18 +777,17 @@ static void skip_emulated_instruction(struct kvm_vcpu *vcpu) 
		svm->next_rip = svm->vmcb->control.next_rip;

	}



	if (!svm->next_rip) {

		if (kvm_emulate_instruction(vcpu, EMULTYPE_SKIP) !=

				EMULATE_DONE)

			printk(KERN_DEBUG "%s: NOP\n", __func__);

		return;

	}

	if (!svm->next_rip)

		return kvm_emulate_instruction(vcpu, EMULTYPE_SKIP);



	if (svm->next_rip - kvm_rip_read(vcpu) > MAX_INST_SIZE)

		printk(KERN_ERR "%s: ip 0x%lx next 0x%llx\n",

		       __func__, kvm_rip_read(vcpu), svm->next_rip);



	kvm_rip_write(vcpu, svm->next_rip);

	svm_set_interrupt_shadow(vcpu, 0);



	return EMULATE_DONE;

}



static void svm_queue_exception(struct kvm_vcpu *vcpu)
@@ -819,7 +818,7 @@ static void svm_queue_exception(struct kvm_vcpu *vcpu) 
		 * raises a fault that is not intercepted. Still better than

		 * failing in all cases.

		 */

		skip_emulated_instruction(&svm->vcpu);

		(void)skip_emulated_instruction(&svm->vcpu);

		rip = kvm_rip_read(&svm->vcpu);

		svm->int3_rip = rip + svm->vmcb->save.cs.base;

		svm->int3_injected = rip - old_rip;
@@ -3896,21 +3895,26 @@ static int task_switch_interception(struct vcpu_svm *svm) 
	if (reason != TASK_SWITCH_GATE ||

	    int_type == SVM_EXITINTINFO_TYPE_SOFT ||

	    (int_type == SVM_EXITINTINFO_TYPE_EXEPT &&

	     (int_vec == OF_VECTOR || int_vec == BP_VECTOR)))

		skip_emulated_instruction(&svm->vcpu);

	     (int_vec == OF_VECTOR || int_vec == BP_VECTOR))) {

		if (skip_emulated_instruction(&svm->vcpu) != EMULATE_DONE)

			goto fail;

	}



	if (int_type != SVM_EXITINTINFO_TYPE_SOFT)

		int_vec = -1;



	if (kvm_task_switch(&svm->vcpu, tss_selector, int_vec, reason,

				has_error_code, error_code) == EMULATE_FAIL) {

				has_error_code, error_code) == EMULATE_FAIL)

		goto fail;



	return 1;



fail:

	svm->vcpu.run->exit_reason = KVM_EXIT_INTERNAL_ERROR;

	svm->vcpu.run->internal.suberror = KVM_INTERNAL_ERROR_EMULATION;

	svm->vcpu.run->internal.ndata = 0;

	return 0;

}

	return 1;

}



static int cpuid_interception(struct vcpu_svm *svm)

{

arch/x86/kvm/vmx/vmx.c

+13 −3
Original line number Diff line number Diff line
@@ -1472,8 +1472,11 @@ static int vmx_rtit_ctl_check(struct kvm_vcpu *vcpu, u64 data) 
	return 0;

}





static void skip_emulated_instruction(struct kvm_vcpu *vcpu)

/*

 * Returns an int to be compatible with SVM implementation (which can fail).

 * Do not use directly, use skip_emulated_instruction() instead.

 */

static int __skip_emulated_instruction(struct kvm_vcpu *vcpu)

{

	unsigned long rip;
@@ -1483,6 +1486,13 @@ static void skip_emulated_instruction(struct kvm_vcpu *vcpu) 


	/* skipping an emulated instruction also counts */

	vmx_set_interrupt_shadow(vcpu, 0);



	return EMULATE_DONE;

}



static inline void skip_emulated_instruction(struct kvm_vcpu *vcpu)

{

	(void)__skip_emulated_instruction(vcpu);

}



static void vmx_clear_hlt(struct kvm_vcpu *vcpu)
@@ -7705,7 +7715,7 @@ static struct kvm_x86_ops vmx_x86_ops __ro_after_init = { 


	.run = vmx_vcpu_run,

	.handle_exit = vmx_handle_exit,

	.skip_emulated_instruction = skip_emulated_instruction,

	.skip_emulated_instruction = __skip_emulated_instruction,

	.set_interrupt_shadow = vmx_set_interrupt_shadow,

	.get_interrupt_shadow = vmx_get_interrupt_shadow,

	.patch_hypercall = vmx_patch_hypercall,

arch/x86/kvm/x86.c

+4 −2
Original line number Diff line number Diff line
@@ -6390,9 +6390,11 @@ static void kvm_vcpu_do_singlestep(struct kvm_vcpu *vcpu, int *r) 
int kvm_skip_emulated_instruction(struct kvm_vcpu *vcpu)

{

	unsigned long rflags = kvm_x86_ops->get_rflags(vcpu);

	int r = EMULATE_DONE;

	int r;



	kvm_x86_ops->skip_emulated_instruction(vcpu);

	r = kvm_x86_ops->skip_emulated_instruction(vcpu);

	if (unlikely(r != EMULATE_DONE))

		return 0;



	/*

	 * rflags is the old, "raw" value of the flags.  The new value has

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