Re: [PATCH 2/6] KVM: selftests: Stash the host page size in a global in the guest_memfd test

Fuad Tabba
2025-09-29T09:13:28Z

On Fri, 26 Sept 2025 at 17:31, Sean Christopherson <seanjc@google.com> wrote:
>
> Use a global variable to track the host page size in the guest_memfd test
> so that the information doesn't need to be constantly passed around. The
> state is purely a reflection of the underlying system, i.e. can't be set
> by the test and is constant for a given invocation of the test, and thus
> explicitly passing the host page size to individual testcases adds no
> value, e.g. doesn't allow testing different combinations.
>
> Making page_size a global will simplify an upcoming change to create a new
> guest_memfd instance per testcase.
>
> No functional change intended.
>
> Signed-off-by: Sean Christopherson <seanjc@google.com>

Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Fuad Tabba <tabba@google.com>

Cheers,
/fuad

> ---
> .../testing/selftests/kvm/guest_memfd_test.c | 37 +++++++++----------
> 1 file changed, 18 insertions(+), 19 deletions(-)
>
> diff --git a/tools/testing/selftests/kvm/guest_memfd_test.c b/tools/testing/selftests/kvm/guest_memfd_test.c
> index 81b11a958c7a..8251d019206a 100644
> --- a/tools/testing/selftests/kvm/guest_memfd_test.c
> +++ b/tools/testing/selftests/kvm/guest_memfd_test.c
> @@ -24,6 +24,8 @@
> #include "test_util.h"
> #include "ucall_common.h"
>
> +static size_t page_size;
> +
> static void test_file_read_write(int fd)
> {
> char buf[64];
> @@ -38,7 +40,7 @@ static void test_file_read_write(int fd)
> "pwrite on a guest_mem fd should fail");
> }
>
> -static void test_mmap_supported(int fd, size_t page_size, size_t total_size)
> +static void test_mmap_supported(int fd, size_t total_size)
> {
> const char val = 0xaa;
> char *mem;
> @@ -78,7 +80,7 @@ void fault_sigbus_handler(int signum)
> siglongjmp(jmpbuf, 1);
> }
>
> -static void test_fault_overflow(int fd, size_t page_size, size_t total_size)
> +static void test_fault_overflow(int fd, size_t total_size)
> {
> struct sigaction sa_old, sa_new = {
> .sa_handler = fault_sigbus_handler,
> @@ -106,7 +108,7 @@ static void test_fault_overflow(int fd, size_t page_size, size_t total_size)
> TEST_ASSERT(!ret, "munmap() should succeed.");
> }
>
> -static void test_mmap_not_supported(int fd, size_t page_size, size_t total_size)
> +static void test_mmap_not_supported(int fd, size_t total_size)
> {
> char *mem;
>
> @@ -117,7 +119,7 @@ static void test_mmap_not_supported(int fd, size_t page_size, size_t total_size)
> TEST_ASSERT_EQ(mem, MAP_FAILED);
> }
>
> -static void test_file_size(int fd, size_t page_size, size_t total_size)
> +static void test_file_size(int fd, size_t total_size)
> {
> struct stat sb;
> int ret;
> @@ -128,7 +130,7 @@ static void test_file_size(int fd, size_t page_size, size_t total_size)
> TEST_ASSERT_EQ(sb.st_blksize, page_size);
> }
>
> -static void test_fallocate(int fd, size_t page_size, size_t total_size)
> +static void test_fallocate(int fd, size_t total_size)
> {
> int ret;
>
> @@ -165,7 +167,7 @@ static void test_fallocate(int fd, size_t page_size, size_t total_size)
> TEST_ASSERT(!ret, "fallocate to restore punched hole should succeed");
> }
>
> -static void test_invalid_punch_hole(int fd, size_t page_size, size_t total_size)
> +static void test_invalid_punch_hole(int fd, size_t total_size)
> {
> struct {
> off_t offset;
> @@ -196,8 +198,7 @@ static void test_invalid_punch_hole(int fd, size_t page_size, size_t total_size)
> }
>
> static void test_create_guest_memfd_invalid_sizes(struct kvm_vm *vm,
> - uint64_t guest_memfd_flags,
> - size_t page_size)
> + uint64_t guest_memfd_flags)
> {
> size_t size;
> int fd;
> @@ -214,7 +215,6 @@ static void test_create_guest_memfd_multiple(struct kvm_vm *vm)
> {
> int fd1, fd2, ret;
> struct stat st1, st2;
> - size_t page_size = getpagesize();
>
> fd1 = __vm_create_guest_memfd(vm, page_size, 0);
> TEST_ASSERT(fd1 != -1, "memfd creation should succeed");
> @@ -241,7 +241,6 @@ static void test_create_guest_memfd_multiple(struct kvm_vm *vm)
>
> static void test_guest_memfd_flags(struct kvm_vm *vm, uint64_t valid_flags)
> {
> - size_t page_size = getpagesize();
> uint64_t flag;
> int fd;
>
> @@ -265,10 +264,8 @@ static void test_guest_memfd(unsigned long vm_type)
> uint64_t flags = 0;
> struct kvm_vm *vm;
> size_t total_size;
> - size_t page_size;
> int fd;
>
> - page_size = getpagesize();
> total_size = page_size * 4;
>
> vm = vm_create_barebones_type(vm_type);
> @@ -277,22 +274,22 @@ static void test_guest_memfd(unsigned long vm_type)
> flags |= GUEST_MEMFD_FLAG_MMAP | GUEST_MEMFD_FLAG_DEFAULT_SHARED;
>
> test_create_guest_memfd_multiple(vm);
> - test_create_guest_memfd_invalid_sizes(vm, flags, page_size);
> + test_create_guest_memfd_invalid_sizes(vm, flags);
>
> fd = vm_create_guest_memfd(vm, total_size, flags);
>
> test_file_read_write(fd);
>
> if (flags & GUEST_MEMFD_FLAG_MMAP) {
> - test_mmap_supported(fd, page_size, total_size);
> - test_fault_overflow(fd, page_size, total_size);
> + test_mmap_supported(fd, total_size);
> + test_fault_overflow(fd, total_size);
> } else {
> - test_mmap_not_supported(fd, page_size, total_size);
> + test_mmap_not_supported(fd, total_size);
> }
>
> - test_file_size(fd, page_size, total_size);
> - test_fallocate(fd, page_size, total_size);
> - test_invalid_punch_hole(fd, page_size, total_size);
> + test_file_size(fd, total_size);
> + test_fallocate(fd, total_size);
> + test_invalid_punch_hole(fd, total_size);
>
> test_guest_memfd_flags(vm, flags);
>
> @@ -367,6 +364,8 @@ int main(int argc, char *argv[])
>
> TEST_REQUIRE(kvm_has_cap(KVM_CAP_GUEST_MEMFD));
>
> + page_size = getpagesize();
> +
> /*
> * Not all architectures support KVM_CAP_VM_TYPES. However, those that
> * support guest_memfd have that support for the default VM type.
> --
> 2.51.0.536.g15c5d4f767-goog
>