Commit 6abe9c13 authored by Peter Xu's avatar Peter Xu Committed by Paolo Bonzini
Browse files

KVM: X86: Move ignore_msrs handling upper the stack 



MSR accesses can be one of:

  (1) KVM internal access,
  (2) userspace access (e.g., via KVM_SET_MSRS ioctl),
  (3) guest access.

The ignore_msrs was previously handled by kvm_get_msr_common() and
kvm_set_msr_common(), which is the bottom of the msr access stack.  It's
working in most cases, however it could dump unwanted warning messages to dmesg
even if kvm get/set the msrs internally when calling __kvm_set_msr() or
__kvm_get_msr() (e.g. kvm_cpuid()).  Ideally we only want to trap cases (2)
or (3), but not (1) above.

To achieve this, move the ignore_msrs handling upper until the callers of
__kvm_get_msr() and __kvm_set_msr().  To identify the "msr missing" event, a
new return value (KVM_MSR_RET_INVALID==2) is used for that.

Signed-off-by: default avatarPeter Xu <peterx@redhat.com>
Message-Id: <20200622220442.21998-2-peterx@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 02f5fb2e

arch/x86/kvm/x86.c

+54 −26
Original line number Diff line number Diff line
@@ -243,6 +243,29 @@ static struct kmem_cache *x86_fpu_cache; 


static struct kmem_cache *x86_emulator_cache;



/*

 * When called, it means the previous get/set msr reached an invalid msr.

 * Return 0 if we want to ignore/silent this failed msr access, or 1 if we want

 * to fail the caller.

 */

static int kvm_msr_ignored_check(struct kvm_vcpu *vcpu, u32 msr,

				 u64 data, bool write)

{

	const char *op = write ? "wrmsr" : "rdmsr";



	if (ignore_msrs) {

		if (report_ignored_msrs)

			vcpu_unimpl(vcpu, "ignored %s: 0x%x data 0x%llx\n",

				    op, msr, data);

		/* Mask the error */

		return 0;

	} else {

		vcpu_debug_ratelimited(vcpu, "unhandled %s: 0x%x data 0x%llx\n",

				       op, msr, data);

		return 1;

	}

}



static struct kmem_cache *kvm_alloc_emulator_cache(void)

{

	unsigned int useroffset = offsetof(struct x86_emulate_ctxt, src);
@@ -1516,6 +1539,17 @@ static int __kvm_set_msr(struct kvm_vcpu *vcpu, u32 index, u64 data, 
	return kvm_x86_ops.set_msr(vcpu, &msr);

}



static int kvm_set_msr_ignored_check(struct kvm_vcpu *vcpu,

				     u32 index, u64 data, bool host_initiated)

{

	int ret = __kvm_set_msr(vcpu, index, data, host_initiated);



	if (ret == KVM_MSR_RET_INVALID)

		ret = kvm_msr_ignored_check(vcpu, index, data, true);



	return ret;

}



/*

 * Read the MSR specified by @index into @data.  Select MSR specific fault

 * checks are bypassed if @host_initiated is %true.
@@ -1537,15 +1571,29 @@ int __kvm_get_msr(struct kvm_vcpu *vcpu, u32 index, u64 *data, 
	return ret;

}



static int kvm_get_msr_ignored_check(struct kvm_vcpu *vcpu,

				     u32 index, u64 *data, bool host_initiated)

{

	int ret = __kvm_get_msr(vcpu, index, data, host_initiated);



	if (ret == KVM_MSR_RET_INVALID) {

		/* Unconditionally clear *data for simplicity */

		*data = 0;

		ret = kvm_msr_ignored_check(vcpu, index, 0, false);

	}



	return ret;

}



int kvm_get_msr(struct kvm_vcpu *vcpu, u32 index, u64 *data)

{

	return __kvm_get_msr(vcpu, index, data, false);

	return kvm_get_msr_ignored_check(vcpu, index, data, false);

}

EXPORT_SYMBOL_GPL(kvm_get_msr);



int kvm_set_msr(struct kvm_vcpu *vcpu, u32 index, u64 data)

{

	return __kvm_set_msr(vcpu, index, data, false);

	return kvm_set_msr_ignored_check(vcpu, index, data, false);

}

EXPORT_SYMBOL_GPL(kvm_set_msr);
@@ -1665,12 +1713,12 @@ EXPORT_SYMBOL_GPL(handle_fastpath_set_msr_irqoff); 
 */

static int do_get_msr(struct kvm_vcpu *vcpu, unsigned index, u64 *data)

{

	return __kvm_get_msr(vcpu, index, data, true);

	return kvm_get_msr_ignored_check(vcpu, index, data, true);

}



static int do_set_msr(struct kvm_vcpu *vcpu, unsigned index, u64 *data)

{

	return __kvm_set_msr(vcpu, index, *data, true);

	return kvm_set_msr_ignored_check(vcpu, index, *data, true);

}



#ifdef CONFIG_X86_64
@@ -3066,17 +3114,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info) 
			return xen_hvm_config(vcpu, data);

		if (kvm_pmu_is_valid_msr(vcpu, msr))

			return kvm_pmu_set_msr(vcpu, msr_info);

		if (!ignore_msrs) {

			vcpu_debug_ratelimited(vcpu, "unhandled wrmsr: 0x%x data 0x%llx\n",

				    msr, data);

			return 1;

		} else {

			if (report_ignored_msrs)

				vcpu_unimpl(vcpu,

					"ignored wrmsr: 0x%x data 0x%llx\n",

					msr, data);

			break;

		}

		return KVM_MSR_RET_INVALID;

	}

	return 0;

}
@@ -3331,17 +3369,7 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info) 
	default:

		if (kvm_pmu_is_valid_msr(vcpu, msr_info->index))

			return kvm_pmu_get_msr(vcpu, msr_info);

		if (!ignore_msrs) {

			vcpu_debug_ratelimited(vcpu, "unhandled rdmsr: 0x%x\n",

					       msr_info->index);

			return 1;

		} else {

			if (report_ignored_msrs)

				vcpu_unimpl(vcpu, "ignored rdmsr: 0x%x\n",

					msr_info->index);

			msr_info->data = 0;

		}

		break;

		return KVM_MSR_RET_INVALID;

	}

	return 0;

}

arch/x86/kvm/x86.h

+2 −0
Original line number Diff line number Diff line
@@ -366,4 +366,6 @@ void kvm_load_host_xsave_state(struct kvm_vcpu *vcpu); 
u64 kvm_spec_ctrl_valid_bits(struct kvm_vcpu *vcpu);

bool kvm_vcpu_exit_request(struct kvm_vcpu *vcpu);



#define  KVM_MSR_RET_INVALID  2



#endif

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