Re: [PATCH v2 8/9] KVM: selftests: Add infrastructure for getting vCPU binary stats

[Manali Shukla <manali.shukla@amd.com>]

On 1/11/2025 6:20 AM, Sean Christopherson wrote:
> Now that the binary stats cache infrastructure is largely scope agnostic,
> add support for vCPU-scoped stats.  Like VM stats, open and cache the
> stats FD when the vCPU is created so that it's guaranteed to be valid when
> vcpu_get_stats() is invoked.
> 
> Account for the extra per-vCPU file descriptor in kvm_set_files_rlimit(),
> so that tests that create large VMs don't run afoul of resource limits.
> 
> To sanity check that the infrastructure actually works, and to get a bit
> of bonus coverage, add an assert in x86's xapic_ipi_test to verify that
> the number of HLTs executed by the test matches the number of HLT exits
> observed by KVM.
> 
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> ---
>  .../testing/selftests/kvm/include/kvm_util.h  | 20 +++++++-----
>  tools/testing/selftests/kvm/lib/kvm_util.c    | 32 ++++++++-----------
>  .../selftests/kvm/x86/xapic_ipi_test.c        |  2 ++
>  3 files changed, 27 insertions(+), 27 deletions(-)
> 
> diff --git a/tools/testing/selftests/kvm/include/kvm_util.h b/tools/testing/selftests/kvm/include/kvm_util.h
> index d4670b5962ab..373912464fb4 100644
> --- a/tools/testing/selftests/kvm/include/kvm_util.h
> +++ b/tools/testing/selftests/kvm/include/kvm_util.h
> @@ -61,6 +61,7 @@ struct kvm_vcpu {
>  #ifdef __x86_64__
>  	struct kvm_cpuid2 *cpuid;
>  #endif
> +	struct kvm_binary_stats stats;
>  	struct kvm_dirty_gfn *dirty_gfns;
>  	uint32_t fetch_index;
>  	uint32_t dirty_gfns_count;
> @@ -534,17 +535,20 @@ void read_stat_data(int stats_fd, struct kvm_stats_header *header,
>  		    struct kvm_stats_desc *desc, uint64_t *data,
>  		    size_t max_elements);
>  
> -void __vm_get_stat(struct kvm_vm *vm, const char *stat_name, uint64_t *data,
> -		   size_t max_elements);
> +void kvm_get_stat(struct kvm_binary_stats *stats, const char *name,
> +		  uint64_t *data, size_t max_elements);
>  
> -#define vm_get_stat(vm, stat)				\
> -({							\
> -	uint64_t data;					\
> -							\
> -	__vm_get_stat(vm, #stat, &data, 1);		\
> -	data;						\
> +#define __get_stat(stats, stat)							\
> +({										\
> +	uint64_t data;								\
> +										\
> +	kvm_get_stat(stats, #stat, &data, 1);					\
> +	data;									\
>  })
>  
> +#define vm_get_stat(vm, stat) __get_stat(&(vm)->stats, stat)
> +#define vcpu_get_stat(vcpu, stat) __get_stat(&(vcpu)->stats, stat)
> +
>  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 f49bb504fa72..b1c3c7260902 100644
> --- a/tools/testing/selftests/kvm/lib/kvm_util.c
> +++ b/tools/testing/selftests/kvm/lib/kvm_util.c
> @@ -415,10 +415,11 @@ static uint64_t vm_nr_pages_required(enum vm_guest_mode mode,
>  void kvm_set_files_rlimit(uint32_t nr_vcpus)
>  {
>  	/*
> -	 * Number of file descriptors required, nr_vpucs vCPU fds + an arbitrary
> -	 * number for everything else.
> +	 * Each vCPU will open two file descriptors: the vCPU itself and the
> +	 * vCPU's binary stats file descriptor.  Add an arbitrary amount of
> +	 * buffer for all other files a test may open.
>  	 */
> -	int nr_fds_wanted = nr_vcpus + 100;
> +	int nr_fds_wanted = nr_vcpus * 2 + 100;
>  	struct rlimit rl;
>  
>  	/*
> @@ -746,6 +747,8 @@ static void vm_vcpu_rm(struct kvm_vm *vm, struct kvm_vcpu *vcpu)
>  	ret = close(vcpu->fd);
>  	TEST_ASSERT(!ret,  __KVM_SYSCALL_ERROR("close()", ret));
>  
> +	kvm_stats_release(&vcpu->stats);
> +
>  	list_del(&vcpu->list);
>  
>  	vcpu_arch_free(vcpu);
> @@ -1339,6 +1342,11 @@ struct kvm_vcpu *__vm_vcpu_add(struct kvm_vm *vm, uint32_t vcpu_id)
>  	TEST_ASSERT(vcpu->run != MAP_FAILED,
>  		    __KVM_SYSCALL_ERROR("mmap()", (int)(unsigned long)MAP_FAILED));
>  
> +	if (kvm_has_cap(KVM_CAP_BINARY_STATS_FD))
> +		vcpu->stats.fd = vcpu_get_stats_fd(vcpu);
> +	else
> +		vcpu->stats.fd = -1;
> +
>  	/* Add to linked-list of VCPUs. */
>  	list_add(&vcpu->list, &vm->vcpus);
>  
> @@ -2251,23 +2259,9 @@ void read_stat_data(int stats_fd, struct kvm_stats_header *header,
>  		    desc->name, size, ret);
>  }
>  
> -/*
> - * Read the data of the named stat
> - *
> - * Input Args:
> - *   vm - the VM 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 __vm_get_stat(struct kvm_vm *vm, const char *name, uint64_t *data,
> -		   size_t max_elements)
> +void kvm_get_stat(struct kvm_binary_stats *stats, const char *name,
> +		  uint64_t *data, size_t max_elements)
>  {
> -	struct kvm_binary_stats *stats = &vm->stats;
>  	struct kvm_stats_desc *desc;
>  	size_t size_desc;
>  	int i;
> diff --git a/tools/testing/selftests/kvm/x86/xapic_ipi_test.c b/tools/testing/selftests/kvm/x86/xapic_ipi_test.c
> index a76078a08ff8..574a944763b7 100644
> --- a/tools/testing/selftests/kvm/x86/xapic_ipi_test.c
> +++ b/tools/testing/selftests/kvm/x86/xapic_ipi_test.c
> @@ -465,6 +465,8 @@ int main(int argc, char *argv[])
>  	cancel_join_vcpu_thread(threads[0], params[0].vcpu);
>  	cancel_join_vcpu_thread(threads[1], params[1].vcpu);
>  
> +	TEST_ASSERT_EQ(data->hlt_count, vcpu_get_stat(params[0].vcpu, halt_exits));
> +
>  	fprintf(stderr,
>  		"Test successful after running for %d seconds.\n"
>  		"Sending vCPU sent %lu IPIs to halting vCPU\n"

I have tested this infrastructure with xapic_ipi_test and ipi hlt test [1] on AMD system.

Tested-by: Manali Shukla <Manali.Shukla@amd.com>

[1]: https://lore.kernel.org/kvm/20250103081828.7060-1-manali.shukla@amd.com/T/#mda361fc0892e6949d98de2a4a79f68fc362a2893


-Manali