Re: [PATCH kvm-next V11 7/7] KVM: guest_memfd: selftests: Add tests for mmap and NUMA policy support

[Sean Christopherson <seanjc@google.com>]

On Wed, Aug 27, 2025, Shivank Garg wrote:
> Add tests for NUMA memory policy binding and NUMA aware allocation in
> guest_memfd. This extends the existing selftests by adding proper
> validation for:
> - KVM GMEM set_policy and get_policy() vm_ops functionality using
>   mbind() and get_mempolicy()
> - NUMA policy application before and after memory allocation
> 
> These tests help ensure NUMA support for guest_memfd works correctly.
> 
> Signed-off-by: Shivank Garg <shivankg@amd.com>
> ---
>  tools/testing/selftests/kvm/Makefile.kvm      |   1 +
>  .../testing/selftests/kvm/guest_memfd_test.c  | 121 ++++++++++++++++++
>  2 files changed, 122 insertions(+)
> 
> diff --git a/tools/testing/selftests/kvm/Makefile.kvm b/tools/testing/selftests/kvm/Makefile.kvm
> index 90f03f00cb04..c46cef2a7cd7 100644
> --- a/tools/testing/selftests/kvm/Makefile.kvm
> +++ b/tools/testing/selftests/kvm/Makefile.kvm
> @@ -275,6 +275,7 @@ pgste-option = $(call try-run, echo 'int main(void) { return 0; }' | \
>  	$(CC) -Werror -Wl$(comma)--s390-pgste -x c - -o "$$TMP",-Wl$(comma)--s390-pgste)
>  
>  LDLIBS += -ldl
> +LDLIBS += -lnuma

Hrm, this is going to be very annoying.  I don't have libnuma-dev installed on
any of my <too many> systems, and I doubt I'm alone.  Installing the package is
trivial, but I'm a little wary of foisting that requirement on all KVM developers
and build bots.

I'd be especially curious what ARM and RISC-V think, as NUMA is likely a bit less
prevelant there.

>  LDFLAGS += -pthread $(no-pie-option) $(pgste-option)
>  
>  LIBKVM_C := $(filter %.c,$(LIBKVM))
> diff --git a/tools/testing/selftests/kvm/guest_memfd_test.c b/tools/testing/selftests/kvm/guest_memfd_test.c
> index b3ca6737f304..9640d04ec293 100644
> --- a/tools/testing/selftests/kvm/guest_memfd_test.c
> +++ b/tools/testing/selftests/kvm/guest_memfd_test.c
> @@ -7,6 +7,8 @@
>  #include <stdlib.h>
>  #include <string.h>
>  #include <unistd.h>
> +#include <numa.h>
> +#include <numaif.h>
>  #include <errno.h>
>  #include <stdio.h>
>  #include <fcntl.h>
> @@ -19,6 +21,7 @@
>  #include <sys/mman.h>
>  #include <sys/types.h>
>  #include <sys/stat.h>
> +#include <sys/syscall.h>
>  
>  #include "kvm_util.h"
>  #include "test_util.h"
> @@ -72,6 +75,122 @@ static void test_mmap_supported(int fd, size_t page_size, size_t total_size)
>  	TEST_ASSERT(!ret, "munmap() should succeed.");
>  }
>  
> +#define TEST_REQUIRE_NUMA_MULTIPLE_NODES()	\
> +	TEST_REQUIRE(numa_available() != -1 && numa_max_node() >= 1)

Using TEST_REQUIRE() here will result in skipping the _entire_ test.  Ideally
this test would use fixtures so that each testcase can run in a child process
and thus can use TEST_REQUIRE(), but that's a conversion for another day.

Easiest thing would probably be to turn this into a common helper and then bail
early.

diff --git a/tools/testing/selftests/kvm/guest_memfd_test.c b/tools/testing/selftests/kvm/guest_memfd_test.c
index 9640d04ec293..6acb186e5300 100644
--- a/tools/testing/selftests/kvm/guest_memfd_test.c
+++ b/tools/testing/selftests/kvm/guest_memfd_test.c
@@ -7,7 +7,6 @@
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
-#include <numa.h>
 #include <numaif.h>
 #include <errno.h>
 #include <stdio.h>
@@ -75,9 +74,6 @@ static void test_mmap_supported(int fd, size_t page_size, size_t total_size)
        TEST_ASSERT(!ret, "munmap() should succeed.");
 }
 
-#define TEST_REQUIRE_NUMA_MULTIPLE_NODES()     \
-       TEST_REQUIRE(numa_available() != -1 && numa_max_node() >= 1)
-
 static void test_mbind(int fd, size_t page_size, size_t total_size)
 {
        unsigned long nodemask = 1; /* nid: 0 */
@@ -87,7 +83,8 @@ static void test_mbind(int fd, size_t page_size, size_t total_size)
        char *mem;
        int ret;
 
-       TEST_REQUIRE_NUMA_MULTIPLE_NODES();
+       if (!is_multi_numa_node_system())
+               return;
 
        mem = mmap(NULL, total_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
        TEST_ASSERT(mem != MAP_FAILED, "mmap for mbind test should succeed");
@@ -136,7 +133,8 @@ static void test_numa_allocation(int fd, size_t page_size, size_t total_size)
        char *mem;
        int ret, i;
 
-       TEST_REQUIRE_NUMA_MULTIPLE_NODES();
+       if (!is_multi_numa_node_system())
+               return;
 
        /* Clean slate: deallocate all file space, if any */
        ret = fallocate(fd, FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE, 0, total_size);
diff --git a/tools/testing/selftests/kvm/include/kvm_util.h b/tools/testing/selftests/kvm/include/kvm_util.h
index 23a506d7eca3..d7051607e6bf 100644
--- a/tools/testing/selftests/kvm/include/kvm_util.h
+++ b/tools/testing/selftests/kvm/include/kvm_util.h
@@ -21,6 +21,7 @@
 #include <sys/eventfd.h>
 #include <sys/ioctl.h>
 
+#include <numa.h>
 #include <pthread.h>
 
 #include "kvm_util_arch.h"
@@ -633,6 +634,11 @@ static inline bool is_smt_on(void)
        return false;
 }
 
+static inline bool is_multi_numa_node_system(void)
+{
+       return numa_available() != -1 && numa_max_node() >= 1;
+}
+
 void vm_create_irqchip(struct kvm_vm *vm);
 
 static inline int __vm_create_guest_memfd(struct kvm_vm *vm, uint64_t size,