diff mbox series

[v3,4/5] KVM: selftests: Add an interface to read the data of named vcpu stat

Message ID 20240528041926.3989-5-manali.shukla@amd.com (mailing list archive)
State New
Headers show
Series Add support for the Idle HLT intercept feature | expand

Commit Message

Manali Shukla May 28, 2024, 4:19 a.m. UTC 
From: Manali Shukla <Manali.Shukla@amd.com>

The interface is used to read the data values of a specified vcpu stat
from the currenly available binary stats interface.

Signed-off-by: Manali Shukla <Manali.Shukla@amd.com>
---
 .../kvm/include/kvm_arch_vcpu_states.h        | 49 +++++++++++++++++++
 .../testing/selftests/kvm/include/kvm_util.h  | 34 +++++++++++++
 tools/testing/selftests/kvm/lib/kvm_util.c    | 32 ++++++++++++
 3 files changed, 115 insertions(+)
 create mode 100644 tools/testing/selftests/kvm/include/kvm_arch_vcpu_states.h

Comments

Sean Christopherson Aug. 13, 2024, 4:37 p.m. UTC | #1 
On Tue, May 28, 2024, Manali Shukla wrote:
> From: Manali Shukla <Manali.Shukla@amd.com>
> 
> The interface is used to read the data values of a specified vcpu stat
> from the currenly available binary stats interface.
> 
> Signed-off-by: Manali Shukla <Manali.Shukla@amd.com>
> ---
>  .../kvm/include/kvm_arch_vcpu_states.h        | 49 +++++++++++++++++++
>  .../testing/selftests/kvm/include/kvm_util.h  | 34 +++++++++++++
>  tools/testing/selftests/kvm/lib/kvm_util.c    | 32 ++++++++++++
>  3 files changed, 115 insertions(+)
>  create mode 100644 tools/testing/selftests/kvm/include/kvm_arch_vcpu_states.h
> 
> diff --git a/tools/testing/selftests/kvm/include/kvm_arch_vcpu_states.h b/tools/testing/selftests/kvm/include/kvm_arch_vcpu_states.h
> new file mode 100644
> index 000000000000..755ff7de53d9
> --- /dev/null
> +++ b/tools/testing/selftests/kvm/include/kvm_arch_vcpu_states.h
> @@ -0,0 +1,49 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +
> +/*
> + * Arch-specific stats are added to the kvm_arch_vcpu_states.h. Sequence
> + * of arch-specific vcpu_stat_type should be same as they are declared in
> + * arch-specific kvm_vcpu_stat.
> + */
> +#ifdef __x86_64__

This is backwards.  If you want arch specific stats, put it them in an arch specific
header.

> +#define KVM_X86_VCPU_STATE(x) KVM_VCPU_STATE(x)
> +
> +KVM_X86_VCPU_STATE(PF_TAKEN)

I'm pretty sure you want KVM_VCPU_STAT, KVM_X86_VCPU_STAT, kvm_arch_vcpu_states.h,
etc.

> +KVM_X86_VCPU_STATE(PF_FIXED)

...

> +/*
> + * Ensure that the sequence of the enum vcpu_stat_types matches the order of
> + * kvm_vcpu_stats_desc[].  Otherwise, vcpu_get_stat() may return incorrect data
> + * because __vcpu_get_stat() uses the enum type as an index to get the
> + * descriptor for a given stat and then uses read_stat_data() to get the stats
> + * from the descriptor.

This isn't maintainable.  Unless I'm missing something, the _order_ of KVM's stats
isn't ABI, and blindly reading an entry and hoping its the right one is doomed to
fail.

I don't see any reason whatsoever to diverge from the core functionality of
__vm_get_stat().  The only difference should be the origin of the stats file and
header.

I do see a lot of room for improvement, but that can and should be done for both
VM and vCPU stats.  E.g. provide an API (and a container/struct?) to get a direct
pointer to stat so that selftests don't have to walk all descriptors when they're
reading the same stat over and over.

And to detect typos at compile time, {vcpu,vm}_get_stat() could either play macro
games or use enums and array to detect usage of a stat that doesn't exist.  E.g.

static inline uint64_t vm_get_stat(struct kvm_vm *vm, int stat)
{
	uint64_t data;

	__vm_get_stat(vm, kvm_vm_stats[stat], &data, 1);
	return data;
}

or 

#define vm_get_stat(vm, stat)			\
({						\
	uin64_t __data;				\
						\
	<concatenation trickery to trigger compiler error if the stat doesn't exit>
	__vm_get_stat(vm, #stat, &data, 1);	\
	data;					\
})

I'd probably vote for macro games, e.g. so that it's all but impossible to pass
a per-VM stat into vcpu_get_stat(), and vice versa.
Manali Shukla Oct. 22, 2024, 5:49 a.m. UTC | #2 
Hi Sean,

Thank you for reviewing my patches. Sorry for the delay in response.

On 8/13/2024 10:07 PM, Sean Christopherson wrote:
> On Tue, May 28, 2024, Manali Shukla wrote:
>> From: Manali Shukla <Manali.Shukla@amd.com>
>>
>> The interface is used to read the data values of a specified vcpu stat
>> from the currenly available binary stats interface.
>>
>> Signed-off-by: Manali Shukla <Manali.Shukla@amd.com>
>> ---
>>  .../kvm/include/kvm_arch_vcpu_states.h        | 49 +++++++++++++++++++
>>  .../testing/selftests/kvm/include/kvm_util.h  | 34 +++++++++++++
>>  tools/testing/selftests/kvm/lib/kvm_util.c    | 32 ++++++++++++
>>  3 files changed, 115 insertions(+)
>>  create mode 100644 tools/testing/selftests/kvm/include/kvm_arch_vcpu_states.h
>>
>> diff --git a/tools/testing/selftests/kvm/include/kvm_arch_vcpu_states.h b/tools/testing/selftests/kvm/include/kvm_arch_vcpu_states.h
>> new file mode 100644
>> index 000000000000..755ff7de53d9
>> --- /dev/null
>> +++ b/tools/testing/selftests/kvm/include/kvm_arch_vcpu_states.h
>> @@ -0,0 +1,49 @@
>> +/* SPDX-License-Identifier: GPL-2.0 */
>> +
>> +/*
>> + * Arch-specific stats are added to the kvm_arch_vcpu_states.h. Sequence
>> + * of arch-specific vcpu_stat_type should be same as they are declared in
>> + * arch-specific kvm_vcpu_stat.
>> + */
>> +#ifdef __x86_64__
> 
> This is backwards.  If you want arch specific stats, put it them in an arch specific
> header.
> 
>> +#define KVM_X86_VCPU_STATE(x) KVM_VCPU_STATE(x)
>> +
>> +KVM_X86_VCPU_STATE(PF_TAKEN)
> 
> I'm pretty sure you want KVM_VCPU_STAT, KVM_X86_VCPU_STAT, kvm_arch_vcpu_states.h,
> etc.
> 
>> +KVM_X86_VCPU_STATE(PF_FIXED)
> 
> ...
> 
>> +/*
>> + * Ensure that the sequence of the enum vcpu_stat_types matches the order of
>> + * kvm_vcpu_stats_desc[].  Otherwise, vcpu_get_stat() may return incorrect data
>> + * because __vcpu_get_stat() uses the enum type as an index to get the
>> + * descriptor for a given stat and then uses read_stat_data() to get the stats
>> + * from the descriptor.
> 
> This isn't maintainable.  Unless I'm missing something, the _order_ of KVM's stats
> isn't ABI, and blindly reading an entry and hoping its the right one is doomed to
> fail.
> 
> I don't see any reason whatsoever to diverge from the core functionality of
> __vm_get_stat().  The only difference should be the origin of the stats file and
> header.
> 
> I do see a lot of room for improvement, but that can and should be done for both
> VM and vCPU stats.  E.g. provide an API (and a container/struct?) to get a direct
> pointer to stat so that selftests don't have to walk all descriptors when they're
> reading the same stat over and over.
> 
> And to detect typos at compile time, {vcpu,vm}_get_stat() could either play macro
> games or use enums and array to detect usage of a stat that doesn't exist.  E.g.
> 
> static inline uint64_t vm_get_stat(struct kvm_vm *vm, int stat)
> {
> 	uint64_t data;
> 
> 	__vm_get_stat(vm, kvm_vm_stats[stat], &data, 1);
> 	return data;
> }
> 
> or 
> 
> #define vm_get_stat(vm, stat)			\
> ({						\
> 	uin64_t __data;				\
> 						\
> 	<concatenation trickery to trigger compiler error if the stat doesn't exit>
> 	__vm_get_stat(vm, #stat, &data, 1);	\
> 	data;					\
> })
> 
> I'd probably vote for macro games, e.g. so that it's all but impossible to pass
> a per-VM stat into vcpu_get_stat(), and vice versa.

All the review comments from this patch are taken care in [1].

[1] https://lore.kernel.org/kvm/20241021062226.108657-1-manali.shukla@amd.com/T/#t

- Manali
diff mbox series

Patch

diff --git a/tools/testing/selftests/kvm/include/kvm_arch_vcpu_states.h b/tools/testing/selftests/kvm/include/kvm_arch_vcpu_states.h
new file mode 100644
index 000000000000..755ff7de53d9
--- /dev/null
+++ b/tools/testing/selftests/kvm/include/kvm_arch_vcpu_states.h
@@ -0,0 +1,49 @@ 
+/* SPDX-License-Identifier: GPL-2.0 */
+
+/*
+ * Arch-specific stats are added to the kvm_arch_vcpu_states.h. Sequence
+ * of arch-specific vcpu_stat_type should be same as they are declared in
+ * arch-specific kvm_vcpu_stat.
+ */
+#ifdef __x86_64__
+#define KVM_X86_VCPU_STATE(x) KVM_VCPU_STATE(x)
+
+KVM_X86_VCPU_STATE(PF_TAKEN)
+KVM_X86_VCPU_STATE(PF_FIXED)
+KVM_X86_VCPU_STATE(PF_EMULATE)
+KVM_X86_VCPU_STATE(PF_SPURIOUS)
+KVM_X86_VCPU_STATE(PF_FAST)
+KVM_X86_VCPU_STATE(PF_MMIO_SPTE_CREATED)
+KVM_X86_VCPU_STATE(PF_GUEST)
+KVM_X86_VCPU_STATE(TLB_FLUSH)
+KVM_X86_VCPU_STATE(INVLPG)
+KVM_X86_VCPU_STATE(EXITS)
+KVM_X86_VCPU_STATE(IO_EXITS)
+KVM_X86_VCPU_STATE(MMIO_EXITS)
+KVM_X86_VCPU_STATE(SIGNAL_EXITS)
+KVM_X86_VCPU_STATE(IRQ_WINDOW_EXITS)
+KVM_X86_VCPU_STATE(NMI_WINDOW_EXITS)
+KVM_X86_VCPU_STATE(LD_FLUSH)
+KVM_X86_VCPU_STATE(HALT_EXITS)
+KVM_X86_VCPU_STATE(REQUEST_IRQ_EXITS)
+KVM_X86_VCPU_STATE(IRQ_EXITS)
+KVM_X86_VCPU_STATE(HOST_STATE_RELOAD)
+KVM_X86_VCPU_STATE(FPU_RELOAD)
+KVM_X86_VCPU_STATE(INSN_EMULATION)
+KVM_X86_VCPU_STATE(INSN_EMULATION_FAIL)
+KVM_X86_VCPU_STATE(HYPERCALLS)
+KVM_X86_VCPU_STATE(IRQ_INJECTIONS)
+KVM_X86_VCPU_STATE(NMI_INJECTIONS)
+KVM_X86_VCPU_STATE(REQ_EVENT)
+KVM_X86_VCPU_STATE(NESTED_RUN)
+KVM_X86_VCPU_STATE(DIRECTED_YIELD_ATTEMPTED)
+KVM_X86_VCPU_STATE(DIRECTED_YIELD_SUCCESSFUL)
+KVM_X86_VCPU_STATE(PREEMPTION_REPORTED)
+KVM_X86_VCPU_STATE(PREEMPTION_OTHER)
+KVM_X86_VCPU_STATE(GUEST_MODE)
+KVM_X86_VCPU_STATE(NOTIFY_WINDOW_EXITS)
+
+#undef KVM_X86_VCPU_STATE
+#undef KVM_VCPU_STATE
+#endif
+
diff --git a/tools/testing/selftests/kvm/include/kvm_util.h b/tools/testing/selftests/kvm/include/kvm_util.h
index 63c2aaae51f3..fe66b1736060 100644
--- a/tools/testing/selftests/kvm/include/kvm_util.h
+++ b/tools/testing/selftests/kvm/include/kvm_util.h
@@ -518,6 +518,40 @@  static inline uint64_t vm_get_stat(struct kvm_vm *vm, const char *stat_name)
 	return data;
 }
 
+/*
+ * Ensure that the sequence of the enum vcpu_stat_types matches the order of
+ * kvm_vcpu_stats_desc[].  Otherwise, vcpu_get_stat() may return incorrect data
+ * because __vcpu_get_stat() uses the enum type as an index to get the
+ * descriptor for a given stat and then uses read_stat_data() to get the stats
+ * from the descriptor.
+ */
+enum vcpu_stat_types {
+	HALT_SUCCESSFUL_POLL,
+	HALT_ATTEMPTED_POLL,
+	HALT_POLL_INVALID,
+	HALT_WAKEUP,
+	HALT_POLL_SUCCESS_NS,
+	HALT_POLL_FAIL_NS,
+	HALT_WAIT_NS,
+	HALT_POLL_SUCCESS_HIST,
+	HALT_POLL_FAIL_HIST,
+	HALT_WAIT_HIST,
+	BLOCKING,
+#define KVM_VCPU_STATE(x)  x,
+#include "kvm_arch_vcpu_states.h"
+};
+
+void __vcpu_get_stat(struct kvm_vcpu *vcpu, enum vcpu_stat_types type, uint64_t *data,
+		   size_t max_elements);
+
+static inline uint64_t vcpu_get_stat(struct kvm_vcpu *vcpu, enum vcpu_stat_types type)
+{
+	uint64_t data;
+
+	__vcpu_get_stat(vcpu, type, &data, 1);
+	return data;
+}
+
 void vm_create_irqchip(struct kvm_vm *vm);
 
 static inline int __vm_create_guest_memfd(struct kvm_vm *vm, uint64_t size,
diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index ad00e4761886..d4b6a352c1ae 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -2264,6 +2264,38 @@  void read_stat_data(int stats_fd, struct kvm_stats_header *header,
 		    desc->name, size, ret);
 }
 
+/*
+ * Read the data of the named vcpu stat
+ *
+ * Input Args:
+ *   vcpu - the vcpu for which the stat should be read
+ *   stat_name - the name of the stat to read
+ *   max_elements - the maximum number of 8-byte values to read into data
+ *
+ * Output Args:
+ *   data - the buffer into which stat data should be read
+ *
+ * Read the data values of a specified stat from the binary stats interface.
+ */
+void __vcpu_get_stat(struct kvm_vcpu *vcpu, enum vcpu_stat_types type, uint64_t *data,
+		   size_t max_elements)
+{
+	int vcpu_stats_fd;
+	struct kvm_stats_header header;
+	struct kvm_stats_desc *desc, *t_desc;
+	size_t size_desc;
+
+	vcpu_stats_fd = vcpu_get_stats_fd(vcpu);
+	read_stats_header(vcpu_stats_fd, &header);
+
+	desc = read_stats_descriptors(vcpu_stats_fd, &header);
+	size_desc = get_stats_descriptor_size(&header);
+
+	t_desc = (void *)desc + (type * size_desc);
+	read_stat_data(vcpu_stats_fd, &header, t_desc,
+			data, max_elements);
+}
+
 /*
  * Read the data of the named stat
  *