Re: [PATCH 5/7] KVM: selftests: Add common helper to get mask+number of usable memory NUMA nodes

[Garg, Shivank]

On Wed, 2026-09-02 at 17:16 -0700, Sean Christopherson wrote:
> Extract and slightly adopt the xAPIC IPI test's logic for getting the mask
> and number of usable memory NUMA nodes into a common helper.  To allow for
> friendlier behavior when the underlying kernel doesn't support NUMA, or the
> test was run without sufficient permissions, zero out the mask and return
> "zero nodes" if get_mempolicy() fails with ENOSYS or EPERM respectively.
> I.e. allow tests to skip (sub)tests instead of throwing an assert.
> 
> Suggested-by: Shivank Garg <shivankg@xxxxxxx>
> Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
> ---
>  tools/testing/selftests/kvm/include/numaif.h     | 13 +++++++++++++
>  tools/testing/selftests/kvm/x86/xapic_ipi_test.c |  5 +----
>  2 files changed, 14 insertions(+), 4 deletions(-)
> 
> diff --git a/tools/testing/selftests/kvm/include/numaif.h b/tools/testing/selftests/kvm/include/numaif.h
> index 299dddff2729..0945500c6322 100644
> --- a/tools/testing/selftests/kvm/include/numaif.h
> +++ b/tools/testing/selftests/kvm/include/numaif.h
> @@ -41,6 +41,19 @@ KVM_SYSCALL_DEFINE(mbind, 6, void *, addr, unsigned long, size, int, mode,
>   */
>  #define MAXNODE_FOR_MASK(mask) (BITS_PER_TYPE(mask) + 1)
>  
> +static inline int kvm_get_numa_memory_nodes(unsigned long *nodemask)
> +{
> +	int r;
> +
> +	*nodemask = 0;
> +
> +	r = get_mempolicy(NULL, nodemask, MAXNODE_FOR_MASK(*nodemask), 0,
> +			  MPOL_F_MEMS_ALLOWED);
> +	TEST_ASSERT(!r || errno == ENOSYS || errno == EPERM,
> +		    "Unexpected get_mempolicy() failure");
> +	return __builtin_popcountl(*nodemask);
> +}
> +
>  /*
>   * Return the node ID of the next NUMA node in the mask, starting at @from+1.
>   * Guarantees a node is found, and that the found node is not @from.  Pass -1
> diff --git a/tools/testing/selftests/kvm/x86/xapic_ipi_test.c b/tools/testing/selftests/kvm/x86/xapic_ipi_test.c
> index 7144ad833ae0..42c601617f5a 100644
> --- a/tools/testing/selftests/kvm/x86/xapic_ipi_test.c
> +++ b/tools/testing/selftests/kvm/x86/xapic_ipi_test.c
> @@ -244,15 +244,12 @@ void do_migrations(struct test_data_page *data, int run_secs, int delay_usecs,
>  	fprintf(stderr, "Calling migrate_pages every %d microseconds\n",
>  		delay_usecs);
>  
> -	/* Get set of first 64 numa nodes available */
> -	kvm_get_mempolicy(NULL, &nodemask, MAXNODE_FOR_MASK(nodemask),
> -			  0, MPOL_F_MEMS_ALLOWED);
> +	nodes = kvm_get_numa_memory_nodes(&nodemask);
>  
>  	fprintf(stderr, "Numa nodes found amongst first %lu possible nodes "
>  		"(each 1-bit indicates node is present): %#lx\n",
>  		BITS_PER_TYPE(nodemask), nodemask);
>  
> -	nodes = __builtin_popcountl(nodemask);
>  	TEST_ASSERT(nodes > 1,
>  		    "Did not find at least 2 numa nodes. Can't do migration");
>  

Reviewed-by: Shivank Garg <shivankg@xxxxxxx>

Thanks,
Shivank