Commit 42188667 authored by Sean Christopherson's avatar Sean Christopherson Committed by Paolo Bonzini
Browse files

KVM: selftests: Add guest_memfd testcase to fault-in on !mmap()'d memory 



Add a guest_memfd testcase to verify that a vCPU can fault-in guest_memfd
memory that supports mmap(), but that is not currently mapped into host
userspace and/or has a userspace address (in the memslot) that points at
something other than the target guest_memfd range.  Mapping guest_memfd
memory into the guest is supposed to operate completely independently from
any userspace mappings.

Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
Message-ID: <20250729225455.670324-25-seanjc@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent a11d7124

tools/testing/selftests/kvm/guest_memfd_test.c

+64 −0
Original line number Diff line number Diff line
@@ -13,6 +13,7 @@ 


#include <linux/bitmap.h>

#include <linux/falloc.h>

#include <linux/sizes.h>

#include <setjmp.h>

#include <signal.h>

#include <sys/mman.h>
@@ -21,6 +22,7 @@ 


#include "kvm_util.h"

#include "test_util.h"

#include "ucall_common.h"



static void test_file_read_write(int fd)

{
@@ -298,6 +300,66 @@ static void test_guest_memfd(unsigned long vm_type) 
	kvm_vm_free(vm);

}



static void guest_code(uint8_t *mem, uint64_t size)

{

	size_t i;



	for (i = 0; i < size; i++)

		__GUEST_ASSERT(mem[i] == 0xaa,

			       "Guest expected 0xaa at offset %lu, got 0x%x", i, mem[i]);



	memset(mem, 0xff, size);

	GUEST_DONE();

}



static void test_guest_memfd_guest(void)

{

	/*

	 * Skip the first 4gb and slot0.  slot0 maps <1gb and is used to back

	 * the guest's code, stack, and page tables, and low memory contains

	 * the PCI hole and other MMIO regions that need to be avoided.

	 */

	const uint64_t gpa = SZ_4G;

	const int slot = 1;



	struct kvm_vcpu *vcpu;

	struct kvm_vm *vm;

	uint8_t *mem;

	size_t size;

	int fd, i;



	if (!kvm_has_cap(KVM_CAP_GUEST_MEMFD_MMAP))

		return;



	vm = __vm_create_shape_with_one_vcpu(VM_SHAPE_DEFAULT, &vcpu, 1, guest_code);



	TEST_ASSERT(vm_check_cap(vm, KVM_CAP_GUEST_MEMFD_MMAP),

		    "Default VM type should always support guest_memfd mmap()");



	size = vm->page_size;

	fd = vm_create_guest_memfd(vm, size, GUEST_MEMFD_FLAG_MMAP);

	vm_set_user_memory_region2(vm, slot, KVM_MEM_GUEST_MEMFD, gpa, size, NULL, fd, 0);



	mem = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);

	TEST_ASSERT(mem != MAP_FAILED, "mmap() on guest_memfd failed");

	memset(mem, 0xaa, size);

	munmap(mem, size);



	virt_pg_map(vm, gpa, gpa);

	vcpu_args_set(vcpu, 2, gpa, size);

	vcpu_run(vcpu);



	TEST_ASSERT_EQ(get_ucall(vcpu, NULL), UCALL_DONE);



	mem = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);

	TEST_ASSERT(mem != MAP_FAILED, "mmap() on guest_memfd failed");

	for (i = 0; i < size; i++)

		TEST_ASSERT_EQ(mem[i], 0xff);



	close(fd);

	kvm_vm_free(vm);

}



int main(int argc, char *argv[])

{

	unsigned long vm_types, vm_type;
@@ -314,4 +376,6 @@ int main(int argc, char *argv[]) 


	for_each_set_bit(vm_type, &vm_types, BITS_PER_TYPE(vm_types))

		test_guest_memfd(vm_type);



	test_guest_memfd_guest();

}