KVM: selftests: aarch64: Relax userfaultfd read vs. write checks

Only Stage1 Page table walks (S1PTW) writing a PTE on an unmapped page
should result in a userfaultfd write. However, the userfaultfd tests in
page_fault_test wrongly assert that any S1PTW is a PTE write.

Fix this by relaxing the read vs. write checks in all userfaultfd
handlers.  Note that this is also an attempt to focus less on KVM (and
userfaultfd) behavior, and more on architectural behavior. Also note
that after commit 406504c ("KVM: arm64: Fix S1PTW handling on RO
memslots"), the userfaultfd fault (S1PTW with AF on an unmaped PTE
page) is actually a read: the translation fault that comes before the
permission fault.

Signed-off-by: Ricardo Koller <[email protected]>
Reviewed-by: Oliver Upton <[email protected]>
Signed-off-by: Marc Zyngier <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Author: Ricardo Koller

tools/testing/selftests/kvm/aarch64/page_fault_test.c

@@ -304,7 +304,7 @@ static struct uffd_args {
 
 /* Returns true to continue the test, and false if it should be skipped. */
 static int uffd_generic_handler(int uffd_mode, int uffd, struct uffd_msg *msg,
-				struct uffd_args *args, bool expect_write)
+				struct uffd_args *args)
 {
 	uint64_t addr = msg->arg.pagefault.address;
 	uint64_t flags = msg->arg.pagefault.flags;
@@ -313,7 +313,6 @@ static int uffd_generic_handler(int uffd_mode, int uffd, struct uffd_msg *msg,
 
 	TEST_ASSERT(uffd_mode == UFFDIO_REGISTER_MODE_MISSING,
 		    "The only expected UFFD mode is MISSING");
-	ASSERT_EQ(!!(flags & UFFD_PAGEFAULT_FLAG_WRITE), expect_write);
 	ASSERT_EQ(addr, (uint64_t)args->hva);
 
 	pr_debug("uffd fault: addr=%p write=%d\n",
@@ -337,19 +336,14 @@ static int uffd_generic_handler(int uffd_mode, int uffd, struct uffd_msg *msg,
 	return 0;
 }
 
-static int uffd_pt_write_handler(int mode, int uffd, struct uffd_msg *msg)
+static int uffd_pt_handler(int mode, int uffd, struct uffd_msg *msg)
 {
-	return uffd_generic_handler(mode, uffd, msg, &pt_args, true);
+	return uffd_generic_handler(mode, uffd, msg, &pt_args);
 }
 
-static int uffd_data_write_handler(int mode, int uffd, struct uffd_msg *msg)
+static int uffd_data_handler(int mode, int uffd, struct uffd_msg *msg)
 {
-	return uffd_generic_handler(mode, uffd, msg, &data_args, true);
-}
-
-static int uffd_data_read_handler(int mode, int uffd, struct uffd_msg *msg)
-{
-	return uffd_generic_handler(mode, uffd, msg, &data_args, false);
+	return uffd_generic_handler(mode, uffd, msg, &data_args);
 }
 
 static void setup_uffd_args(struct userspace_mem_region *region,
@@ -822,7 +816,7 @@ static void help(char *name)
 	.mem_mark_cmd		= CMD_HOLE_DATA | CMD_HOLE_PT,			\
 	.guest_test_check	= { _CHECK(_with_af), _test_check },		\
 	.uffd_data_handler	= _uffd_data_handler,				\
-	.uffd_pt_handler	= uffd_pt_write_handler,			\
+	.uffd_pt_handler	= uffd_pt_handler,				\
 	.expected_events	= { .uffd_faults = _uffd_faults, },		\
 }
 
@@ -878,7 +872,7 @@ static void help(char *name)
 	.guest_prepare		= { _PREPARE(_access) },			\
 	.guest_test		= _access,					\
 	.uffd_data_handler	= _uffd_data_handler,				\
-	.uffd_pt_handler	= uffd_pt_write_handler,			\
+	.uffd_pt_handler	= uffd_pt_handler,				\
 	.mmio_handler		= _mmio_handler,				\
 	.expected_events	= { .mmio_exits = _mmio_exits,			\
 				    .uffd_faults = _uffd_faults },		\
@@ -892,7 +886,7 @@ static void help(char *name)
 	.mem_mark_cmd		= CMD_HOLE_DATA | CMD_HOLE_PT,			\
 	.guest_test		= _access,					\
 	.uffd_data_handler	= _uffd_data_handler,				\
-	.uffd_pt_handler	= uffd_pt_write_handler,			\
+	.uffd_pt_handler	= uffd_pt_handler,			\
 	.fail_vcpu_run_handler	= fail_vcpu_run_mmio_no_syndrome_handler,	\
 	.expected_events	= { .fail_vcpu_runs = 1,			\
 				    .uffd_faults = _uffd_faults },		\
@@ -933,29 +927,27 @@ static struct test_desc tests[] = {
 	 * (S1PTW).
 	 */
 	TEST_UFFD(guest_read64, with_af, CMD_HOLE_DATA | CMD_HOLE_PT,
-		  uffd_data_read_handler, uffd_pt_write_handler, 2),
-	/* no_af should also lead to a PT write. */
+		  uffd_data_handler, uffd_pt_handler, 2),
 	TEST_UFFD(guest_read64, no_af, CMD_HOLE_DATA | CMD_HOLE_PT,
-		  uffd_data_read_handler, uffd_pt_write_handler, 2),
-	/* Note how that cas invokes the read handler. */
+		  uffd_data_handler, uffd_pt_handler, 2),
 	TEST_UFFD(guest_cas, with_af, CMD_HOLE_DATA | CMD_HOLE_PT,
-		  uffd_data_read_handler, uffd_pt_write_handler, 2),
+		  uffd_data_handler, uffd_pt_handler, 2),
 	/*
 	 * Can't test guest_at with_af as it's IMPDEF whether the AF is set.
 	 * The S1PTW fault should still be marked as a write.
 	 */
 	TEST_UFFD(guest_at, no_af, CMD_HOLE_DATA | CMD_HOLE_PT,
-		  uffd_data_read_handler, uffd_pt_write_handler, 1),
+		  uffd_no_handler, uffd_pt_handler, 1),
 	TEST_UFFD(guest_ld_preidx, with_af, CMD_HOLE_DATA | CMD_HOLE_PT,
-		  uffd_data_read_handler, uffd_pt_write_handler, 2),
+		  uffd_data_handler, uffd_pt_handler, 2),
 	TEST_UFFD(guest_write64, with_af, CMD_HOLE_DATA | CMD_HOLE_PT,
-		  uffd_data_write_handler, uffd_pt_write_handler, 2),
+		  uffd_data_handler, uffd_pt_handler, 2),
 	TEST_UFFD(guest_dc_zva, with_af, CMD_HOLE_DATA | CMD_HOLE_PT,
-		  uffd_data_write_handler, uffd_pt_write_handler, 2),
+		  uffd_data_handler, uffd_pt_handler, 2),
 	TEST_UFFD(guest_st_preidx, with_af, CMD_HOLE_DATA | CMD_HOLE_PT,
-		  uffd_data_write_handler, uffd_pt_write_handler, 2),
+		  uffd_data_handler, uffd_pt_handler, 2),
 	TEST_UFFD(guest_exec, with_af, CMD_HOLE_DATA | CMD_HOLE_PT,
-		  uffd_data_read_handler, uffd_pt_write_handler, 2),
+		  uffd_data_handler, uffd_pt_handler, 2),
 
 	/*
 	 * Try accesses when the data and PT memory regions are both
@@ -980,25 +972,25 @@ static struct test_desc tests[] = {
 	 * fault, and nothing in the dirty log.  Any S1PTW should result in
 	 * a write in the dirty log and a userfaultfd write.
 	 */
-	TEST_UFFD_AND_DIRTY_LOG(guest_read64, with_af, uffd_data_read_handler, 2,
+	TEST_UFFD_AND_DIRTY_LOG(guest_read64, with_af, uffd_data_handler, 2,
 				guest_check_no_write_in_dirty_log),
 	/* no_af should also lead to a PT write. */
-	TEST_UFFD_AND_DIRTY_LOG(guest_read64, no_af, uffd_data_read_handler, 2,
+	TEST_UFFD_AND_DIRTY_LOG(guest_read64, no_af, uffd_data_handler, 2,
 				guest_check_no_write_in_dirty_log),
-	TEST_UFFD_AND_DIRTY_LOG(guest_ld_preidx, with_af, uffd_data_read_handler,
+	TEST_UFFD_AND_DIRTY_LOG(guest_ld_preidx, with_af, uffd_data_handler,
 				2, guest_check_no_write_in_dirty_log),
-	TEST_UFFD_AND_DIRTY_LOG(guest_at, with_af, 0, 1,
+	TEST_UFFD_AND_DIRTY_LOG(guest_at, with_af, uffd_no_handler, 1,
 				guest_check_no_write_in_dirty_log),
-	TEST_UFFD_AND_DIRTY_LOG(guest_exec, with_af, uffd_data_read_handler, 2,
+	TEST_UFFD_AND_DIRTY_LOG(guest_exec, with_af, uffd_data_handler, 2,
 				guest_check_no_write_in_dirty_log),
-	TEST_UFFD_AND_DIRTY_LOG(guest_write64, with_af, uffd_data_write_handler,
+	TEST_UFFD_AND_DIRTY_LOG(guest_write64, with_af, uffd_data_handler,
 				2, guest_check_write_in_dirty_log),
-	TEST_UFFD_AND_DIRTY_LOG(guest_cas, with_af, uffd_data_read_handler, 2,
+	TEST_UFFD_AND_DIRTY_LOG(guest_cas, with_af, uffd_data_handler, 2,
 				guest_check_write_in_dirty_log),
-	TEST_UFFD_AND_DIRTY_LOG(guest_dc_zva, with_af, uffd_data_write_handler,
+	TEST_UFFD_AND_DIRTY_LOG(guest_dc_zva, with_af, uffd_data_handler,
 				2, guest_check_write_in_dirty_log),
 	TEST_UFFD_AND_DIRTY_LOG(guest_st_preidx, with_af,
-				uffd_data_write_handler, 2,
+				uffd_data_handler, 2,
 				guest_check_write_in_dirty_log),
 
 	/*
@@ -1051,22 +1043,15 @@ static struct test_desc tests[] = {
 	 * no userfaultfd write fault. Reads result in userfaultfd getting
 	 * triggered.
 	 */
-	TEST_RO_MEMSLOT_AND_UFFD(guest_read64, 0, 0,
-				 uffd_data_read_handler, 2),
-	TEST_RO_MEMSLOT_AND_UFFD(guest_ld_preidx, 0, 0,
-				 uffd_data_read_handler, 2),
-	TEST_RO_MEMSLOT_AND_UFFD(guest_at, 0, 0,
-				 uffd_no_handler, 1),
-	TEST_RO_MEMSLOT_AND_UFFD(guest_exec, 0, 0,
-				 uffd_data_read_handler, 2),
+	TEST_RO_MEMSLOT_AND_UFFD(guest_read64, 0, 0, uffd_data_handler, 2),
+	TEST_RO_MEMSLOT_AND_UFFD(guest_ld_preidx, 0, 0, uffd_data_handler, 2),
+	TEST_RO_MEMSLOT_AND_UFFD(guest_at, 0, 0, uffd_no_handler, 1),
+	TEST_RO_MEMSLOT_AND_UFFD(guest_exec, 0, 0, uffd_data_handler, 2),
 	TEST_RO_MEMSLOT_AND_UFFD(guest_write64, mmio_on_test_gpa_handler, 1,
-				 uffd_data_write_handler, 2),
-	TEST_RO_MEMSLOT_NO_SYNDROME_AND_UFFD(guest_cas,
-					     uffd_data_read_handler, 2),
-	TEST_RO_MEMSLOT_NO_SYNDROME_AND_UFFD(guest_dc_zva,
-					     uffd_no_handler, 1),
-	TEST_RO_MEMSLOT_NO_SYNDROME_AND_UFFD(guest_st_preidx,
-					     uffd_no_handler, 1),
+				 uffd_data_handler, 2),
+	TEST_RO_MEMSLOT_NO_SYNDROME_AND_UFFD(guest_cas, uffd_data_handler, 2),
+	TEST_RO_MEMSLOT_NO_SYNDROME_AND_UFFD(guest_dc_zva, uffd_no_handler, 1),
+	TEST_RO_MEMSLOT_NO_SYNDROME_AND_UFFD(guest_st_preidx, uffd_no_handler, 1),
 
 	{ 0 }
 };