2021-07-29 13:49:16

by David Edmondson

[permalink] [raw]
Subject: [PATCH v3 1/3] KVM: x86: kvm_x86_ops.get_exit_info should include the exit reason

Extend the get_exit_info static call to provide the reason for the VM
exit. Modify relevant trace points to use this rather than extracting
the reason in the caller.

Signed-off-by: David Edmondson <[email protected]>
---
arch/x86/include/asm/kvm_host.h | 7 ++++---
arch/x86/kvm/svm/svm.c | 8 +++++---
arch/x86/kvm/trace.h | 11 ++++++-----
arch/x86/kvm/vmx/nested.c | 2 +-
arch/x86/kvm/vmx/vmx.c | 6 ++++--
5 files changed, 20 insertions(+), 14 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 974cbfb1eefe..dfb902930cdc 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1377,10 +1377,11 @@ struct kvm_x86_ops {
void (*write_tsc_multiplier)(struct kvm_vcpu *vcpu, u64 multiplier);

/*
- * Retrieve somewhat arbitrary exit information. Intended to be used
- * only from within tracepoints to avoid VMREADs when tracing is off.
+ * Retrieve somewhat arbitrary exit information. Intended to
+ * be used only from within tracepoints or error paths.
*/
- void (*get_exit_info)(struct kvm_vcpu *vcpu, u64 *info1, u64 *info2,
+ void (*get_exit_info)(struct kvm_vcpu *vcpu, u64 *reason,
+ u64 *info1, u64 *info2,
u32 *exit_int_info, u32 *exit_int_info_err_code);

int (*check_intercept)(struct kvm_vcpu *vcpu,
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 664d20f0689c..e5c4354dcc6f 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -3301,11 +3301,13 @@ int svm_invoke_exit_handler(struct kvm_vcpu *vcpu, u64 exit_code)
return svm_exit_handlers[exit_code](vcpu);
}

-static void svm_get_exit_info(struct kvm_vcpu *vcpu, u64 *info1, u64 *info2,
+static void svm_get_exit_info(struct kvm_vcpu *vcpu, u64 *reason,
+ u64 *info1, u64 *info2,
u32 *intr_info, u32 *error_code)
{
struct vmcb_control_area *control = &to_svm(vcpu)->vmcb->control;

+ *reason = control->exit_code;
*info1 = control->exit_info_1;
*info2 = control->exit_info_2;
*intr_info = control->exit_int_info;
@@ -3322,7 +3324,7 @@ static int handle_exit(struct kvm_vcpu *vcpu, fastpath_t exit_fastpath)
struct kvm_run *kvm_run = vcpu->run;
u32 exit_code = svm->vmcb->control.exit_code;

- trace_kvm_exit(exit_code, vcpu, KVM_ISA_SVM);
+ trace_kvm_exit(vcpu, KVM_ISA_SVM);

/* SEV-ES guests must use the CR write traps to track CR registers. */
if (!sev_es_guest(vcpu->kvm)) {
@@ -3335,7 +3337,7 @@ static int handle_exit(struct kvm_vcpu *vcpu, fastpath_t exit_fastpath)
if (is_guest_mode(vcpu)) {
int vmexit;

- trace_kvm_nested_vmexit(exit_code, vcpu, KVM_ISA_SVM);
+ trace_kvm_nested_vmexit(vcpu, KVM_ISA_SVM);

vmexit = nested_svm_exit_special(svm);

diff --git a/arch/x86/kvm/trace.h b/arch/x86/kvm/trace.h
index b484141ea15b..2228565beda2 100644
--- a/arch/x86/kvm/trace.h
+++ b/arch/x86/kvm/trace.h
@@ -273,11 +273,11 @@ TRACE_EVENT(kvm_apic,

#define TRACE_EVENT_KVM_EXIT(name) \
TRACE_EVENT(name, \
- TP_PROTO(unsigned int exit_reason, struct kvm_vcpu *vcpu, u32 isa), \
- TP_ARGS(exit_reason, vcpu, isa), \
+ TP_PROTO(struct kvm_vcpu *vcpu, u32 isa), \
+ TP_ARGS(vcpu, isa), \
\
TP_STRUCT__entry( \
- __field( unsigned int, exit_reason ) \
+ __field( u64, exit_reason ) \
__field( unsigned long, guest_rip ) \
__field( u32, isa ) \
__field( u64, info1 ) \
@@ -288,11 +288,12 @@ TRACE_EVENT(name, \
), \
\
TP_fast_assign( \
- __entry->exit_reason = exit_reason; \
__entry->guest_rip = kvm_rip_read(vcpu); \
__entry->isa = isa; \
__entry->vcpu_id = vcpu->vcpu_id; \
- static_call(kvm_x86_get_exit_info)(vcpu, &__entry->info1, \
+ static_call(kvm_x86_get_exit_info)(vcpu, \
+ &__entry->exit_reason, \
+ &__entry->info1, \
&__entry->info2, \
&__entry->intr_info, \
&__entry->error_code); \
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 1a52134b0c42..fbbc01e9570b 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -6025,7 +6025,7 @@ bool nested_vmx_reflect_vmexit(struct kvm_vcpu *vcpu)
goto reflect_vmexit;
}

- trace_kvm_nested_vmexit(exit_reason.full, vcpu, KVM_ISA_VMX);
+ trace_kvm_nested_vmexit(vcpu, KVM_ISA_VMX);

/* If L0 (KVM) wants the exit, it trumps L1's desires. */
if (nested_vmx_l0_wants_exit(vcpu, exit_reason))
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 927a552393b9..fefdecb0ff3d 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -5617,11 +5617,13 @@ static int (*kvm_vmx_exit_handlers[])(struct kvm_vcpu *vcpu) = {
static const int kvm_vmx_max_exit_handlers =
ARRAY_SIZE(kvm_vmx_exit_handlers);

-static void vmx_get_exit_info(struct kvm_vcpu *vcpu, u64 *info1, u64 *info2,
+static void vmx_get_exit_info(struct kvm_vcpu *vcpu, u64 *reason,
+ u64 *info1, u64 *info2,
u32 *intr_info, u32 *error_code)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);

+ *reason = vmx->exit_reason.full;
*info1 = vmx_get_exit_qual(vcpu);
if (!(vmx->exit_reason.failed_vmentry)) {
*info2 = vmx->idt_vectoring_info;
@@ -6748,7 +6750,7 @@ static fastpath_t vmx_vcpu_run(struct kvm_vcpu *vcpu)
if (likely(!vmx->exit_reason.failed_vmentry))
vmx->idt_vectoring_info = vmcs_read32(IDT_VECTORING_INFO_FIELD);

- trace_kvm_exit(vmx->exit_reason.full, vcpu, KVM_ISA_VMX);
+ trace_kvm_exit(vcpu, KVM_ISA_VMX);

if (unlikely(vmx->exit_reason.failed_vmentry))
return EXIT_FASTPATH_NONE;
--
2.30.2



2021-07-29 22:28:47

by Sean Christopherson

[permalink] [raw]
Subject: Re: [PATCH v3 1/3] KVM: x86: kvm_x86_ops.get_exit_info should include the exit reason

Shortlog is a bit odd, "should" is subjective and makes this sound like a bug fix.

KVM: x86: Get exit_reason as part of kvm_x86_ops.get_exit_info

On Thu, Jul 29, 2021, David Edmondson wrote:
> Extend the get_exit_info static call to provide the reason for the VM
> exit. Modify relevant trace points to use this rather than extracting
> the reason in the caller.
>
> Signed-off-by: David Edmondson <[email protected]>
> ---
> -static void svm_get_exit_info(struct kvm_vcpu *vcpu, u64 *info1, u64 *info2,
> +static void svm_get_exit_info(struct kvm_vcpu *vcpu, u64 *reason,
> + u64 *info1, u64 *info2,
> u32 *intr_info, u32 *error_code)
> {
> struct vmcb_control_area *control = &to_svm(vcpu)->vmcb->control;
>
> + *reason = control->exit_code;
> *info1 = control->exit_info_1;
> *info2 = control->exit_info_2;
> *intr_info = control->exit_int_info;

...

> diff --git a/arch/x86/kvm/trace.h b/arch/x86/kvm/trace.h
> index b484141ea15b..2228565beda2 100644
> --- a/arch/x86/kvm/trace.h
> +++ b/arch/x86/kvm/trace.h
> @@ -273,11 +273,11 @@ TRACE_EVENT(kvm_apic,
>
> #define TRACE_EVENT_KVM_EXIT(name) \
> TRACE_EVENT(name, \
> - TP_PROTO(unsigned int exit_reason, struct kvm_vcpu *vcpu, u32 isa), \
> - TP_ARGS(exit_reason, vcpu, isa), \
> + TP_PROTO(struct kvm_vcpu *vcpu, u32 isa), \
> + TP_ARGS(vcpu, isa), \
> \
> TP_STRUCT__entry( \
> - __field( unsigned int, exit_reason ) \
> + __field( u64, exit_reason ) \

Converting to a u64 is unnecessary and misleading. vmcs.EXIT_REASON and
vmcb.EXIT_CODE are both u32s, a.k.a. unsigned ints. There is vmcb.EXIT_CODE_HI,
but that's not being included, and AFAICT isn't even sanity checked by KVM.

> __field( unsigned long, guest_rip ) \
> __field( u32, isa ) \
> __field( u64, info1 ) \

2021-07-30 07:31:19

by David Edmondson

[permalink] [raw]
Subject: Re: [PATCH v3 1/3] KVM: x86: kvm_x86_ops.get_exit_info should include the exit reason

On Thursday, 2021-07-29 at 22:27:28 GMT, Sean Christopherson wrote:

> Shortlog is a bit odd, "should" is subjective and makes this sound like a bug fix.
>
> KVM: x86: Get exit_reason as part of kvm_x86_ops.get_exit_info

Okay.

> On Thu, Jul 29, 2021, David Edmondson wrote:
>> Extend the get_exit_info static call to provide the reason for the VM
>> exit. Modify relevant trace points to use this rather than extracting
>> the reason in the caller.
>>
>> Signed-off-by: David Edmondson <[email protected]>
>> ---
>> -static void svm_get_exit_info(struct kvm_vcpu *vcpu, u64 *info1, u64 *info2,
>> +static void svm_get_exit_info(struct kvm_vcpu *vcpu, u64 *reason,
>> + u64 *info1, u64 *info2,
>> u32 *intr_info, u32 *error_code)
>> {
>> struct vmcb_control_area *control = &to_svm(vcpu)->vmcb->control;
>>
>> + *reason = control->exit_code;
>> *info1 = control->exit_info_1;
>> *info2 = control->exit_info_2;
>> *intr_info = control->exit_int_info;
>
> ...
>
>> diff --git a/arch/x86/kvm/trace.h b/arch/x86/kvm/trace.h
>> index b484141ea15b..2228565beda2 100644
>> --- a/arch/x86/kvm/trace.h
>> +++ b/arch/x86/kvm/trace.h
>> @@ -273,11 +273,11 @@ TRACE_EVENT(kvm_apic,
>>
>> #define TRACE_EVENT_KVM_EXIT(name) \
>> TRACE_EVENT(name, \
>> - TP_PROTO(unsigned int exit_reason, struct kvm_vcpu *vcpu, u32 isa), \
>> - TP_ARGS(exit_reason, vcpu, isa), \
>> + TP_PROTO(struct kvm_vcpu *vcpu, u32 isa), \
>> + TP_ARGS(vcpu, isa), \
>> \
>> TP_STRUCT__entry( \
>> - __field( unsigned int, exit_reason ) \
>> + __field( u64, exit_reason ) \
>
> Converting to a u64 is unnecessary and misleading. vmcs.EXIT_REASON and
> vmcb.EXIT_CODE are both u32s, a.k.a. unsigned ints. There is vmcb.EXIT_CODE_HI,
> but that's not being included, and AFAICT isn't even sanity checked by KVM.

Thanks for pointing this out, I can only blame brain fade.

>> __field( unsigned long, guest_rip ) \
>> __field( u32, isa ) \
>> __field( u64, info1 ) \