KVM: selftests: Add guest_memfd tests for mmap and NUMA policy support

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

Run the NUMA mbind() test with and without INIT_SHARED, as KVM should allow
doing mbind(), madvise(), etc. on guest-private memory, e.g. so that
userspace can set NUMA policy for CoCo VMs.

Run the NUMA allocation test only for INIT_SHARED, i.e. if the host can't
fault-in memory (via direct access, madvise(), etc.) as move_pages()
returns -ENOENT if the page hasn't been faulted in (walks the host page
tables to find the associated folio)

[sean: don't skip entire test when running on non-NUMA system, test mbind()
with private memory, provide more info in assert messages]

Signed-off-by: Shivank Garg <[e-mail]>
Tested-by: Ashish Kalra <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Sean Christopherson <[e-mail]>

tools/testing/selftests/kvm/guest_memfd_test.c

···
 #include <sys/stat.h>
 
 #include "kvm_util.h"
+#include "numaif.h"
 #include "test_util.h"
 #include "ucall_common.h"
 
···
 	memset(mem, val, page_size);
 	for (i = 0; i < total_size; i++)
 		TEST_ASSERT_EQ(READ_ONCE(mem[i]), val);
+
+	kvm_munmap(mem, total_size);
+}
+
+static void test_mbind(int fd, size_t total_size)
+{
+	const unsigned long nodemask_0 = 1; /* nid: 0 */
+	unsigned long nodemask = 0;
+	unsigned long maxnode = 8;
+	int policy;
+	char *mem;
+	int ret;
+
+	if (!is_multi_numa_node_system())
+		return;
+
+	mem = kvm_mmap(total_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd);
+
+	/* Test MPOL_INTERLEAVE policy */
+	kvm_mbind(mem, page_size * 2, MPOL_INTERLEAVE, &nodemask_0, maxnode, 0);
+	kvm_get_mempolicy(&policy, &nodemask, maxnode, mem, MPOL_F_ADDR);
+	TEST_ASSERT(policy == MPOL_INTERLEAVE && nodemask == nodemask_0,
+		    "Wanted MPOL_INTERLEAVE (%u) and nodemask 0x%lx, got %u and 0x%lx",
+		    MPOL_INTERLEAVE, nodemask_0, policy, nodemask);
+
+	/* Test basic MPOL_BIND policy */
+	kvm_mbind(mem + page_size * 2, page_size * 2, MPOL_BIND, &nodemask_0, maxnode, 0);
+	kvm_get_mempolicy(&policy, &nodemask, maxnode, mem + page_size * 2, MPOL_F_ADDR);
+	TEST_ASSERT(policy == MPOL_BIND && nodemask == nodemask_0,
+		    "Wanted MPOL_BIND (%u) and nodemask 0x%lx, got %u and 0x%lx",
+		    MPOL_BIND, nodemask_0, policy, nodemask);
+
+	/* Test MPOL_DEFAULT policy */
+	kvm_mbind(mem, total_size, MPOL_DEFAULT, NULL, 0, 0);
+	kvm_get_mempolicy(&policy, &nodemask, maxnode, mem, MPOL_F_ADDR);
+	TEST_ASSERT(policy == MPOL_DEFAULT && !nodemask,
+		    "Wanted MPOL_DEFAULT (%u) and nodemask 0x0, got %u and 0x%lx",
+		    MPOL_DEFAULT, policy, nodemask);
+
+	/* Test with invalid policy */
+	ret = mbind(mem, page_size, 999, &nodemask_0, maxnode, 0);
+	TEST_ASSERT(ret == -1 && errno == EINVAL,
+		    "mbind with invalid policy should fail with EINVAL");
+
+	kvm_munmap(mem, total_size);
+}
+
+static void test_numa_allocation(int fd, size_t total_size)
+{
+	unsigned long node0_mask = 1;  /* Node 0 */
+	unsigned long node1_mask = 2;  /* Node 1 */
+	unsigned long maxnode = 8;
+	void *pages[4];
+	int status[4];
+	char *mem;
+	int i;
+
+	if (!is_multi_numa_node_system())
+		return;
+
+	mem = kvm_mmap(total_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd);
+
+	for (i = 0; i < 4; i++)
+		pages[i] = (char *)mem + page_size * i;
+
+	/* Set NUMA policy after allocation */
+	memset(mem, 0xaa, page_size);
+	kvm_mbind(pages[0], page_size, MPOL_BIND, &node0_mask, maxnode, 0);
+	kvm_fallocate(fd, FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE, 0, page_size);
+
+	/* Set NUMA policy before allocation */
+	kvm_mbind(pages[0], page_size * 2, MPOL_BIND, &node1_mask, maxnode, 0);
+	kvm_mbind(pages[2], page_size * 2, MPOL_BIND, &node0_mask, maxnode, 0);
+	memset(mem, 0xaa, total_size);
+
+	/* Validate if pages are allocated on specified NUMA nodes */
+	kvm_move_pages(0, 4, pages, NULL, status, 0);
+	TEST_ASSERT(status[0] == 1, "Expected page 0 on node 1, got it on node %d", status[0]);
+	TEST_ASSERT(status[1] == 1, "Expected page 1 on node 1, got it on node %d", status[1]);
+	TEST_ASSERT(status[2] == 0, "Expected page 2 on node 0, got it on node %d", status[2]);
+	TEST_ASSERT(status[3] == 0, "Expected page 3 on node 0, got it on node %d", status[3]);
+
+	/* Punch hole for all pages */
+	kvm_fallocate(fd, FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE, 0, total_size);
+
+	/* Change NUMA policy nodes and reallocate */
+	kvm_mbind(pages[0], page_size * 2, MPOL_BIND, &node0_mask, maxnode, 0);
+	kvm_mbind(pages[2], page_size * 2, MPOL_BIND, &node1_mask, maxnode, 0);
+	memset(mem, 0xaa, total_size);
+
+	kvm_move_pages(0, 4, pages, NULL, status, 0);
+	TEST_ASSERT(status[0] == 0, "Expected page 0 on node 0, got it on node %d", status[0]);
+	TEST_ASSERT(status[1] == 0, "Expected page 1 on node 0, got it on node %d", status[1]);
+	TEST_ASSERT(status[2] == 1, "Expected page 2 on node 1, got it on node %d", status[2]);
+	TEST_ASSERT(status[3] == 1, "Expected page 3 on node 1, got it on node %d", status[3]);
 
 	kvm_munmap(mem, total_size);
 }
···
 		if (flags & GUEST_MEMFD_FLAG_INIT_SHARED) {
 			gmem_test(mmap_supported, vm, flags);
 			gmem_test(fault_overflow, vm, flags);
+			gmem_test(numa_allocation, vm, flags);
 		} else {
 			gmem_test(fault_private, vm, flags);
 		}
 
 		gmem_test(mmap_cow, vm, flags);
+		gmem_test(mbind, vm, flags);
 	} else {
 		gmem_test(mmap_not_supported, vm, flags);
 	}