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

Sean Christopherson
2025-09-26T16:31:24Z

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>
---
.../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