15136 want unit test for bhyve dirty page tracking

Reviewed by: Greg Colombo <greg@oxidecomputer.com>
Approved by: Dan McDonald <danmcd@mnx.io>

3 files changed, 193 insertions, 1 deletions

diff --git a/usr/src/test/bhyve-tests/tests/inst_emul/Makefile b/usr/src/test/bhyve-tests/tests/inst_emul/Makefile
index 37a8b62b4f..f01a9c3bee 100644
--- a/usr/src/test/bhyve-tests/tests/inst_emul/Makefile
+++ b/usr/src/test/bhyve-tests/tests/inst_emul/Makefile
@@ -23,7 +23,8 @@ PROG =	rdmsr \
 # These should probably go in the `vmm` tests, but since they depend on
 # in-guest payloads, it is easier to build them here.
 PROG +=	triple_fault \
-	exit_paging
+	exit_paging \
+	page_dirty
 
 # C-based payloads need additional utils object
 CPAYLOADS =	cpuid
diff --git a/usr/src/test/bhyve-tests/tests/inst_emul/page_dirty.c b/usr/src/test/bhyve-tests/tests/inst_emul/page_dirty.c
new file mode 100644
index 0000000000..2e3a06bf47
--- /dev/null
+++ b/usr/src/test/bhyve-tests/tests/inst_emul/page_dirty.c
@@ -0,0 +1,162 @@
+/*
+ * This file and its contents are supplied under the terms of the
+ * Common Development and Distribution License ("CDDL"), version 1.0.
+ * You may only use this file in accordance with the terms of version
+ * 1.0 of the CDDL.
+ *
+ * A full copy of the text of the CDDL should have accompanied this
+ * source.  A copy of the CDDL is also available via the Internet at
+ * http://www.illumos.org/license/CDDL.
+ */
+
+/*
+ * Copyright 2022 Oxide Computer Company
+ */
+
+#include <stdio.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <strings.h>
+#include <libgen.h>
+#include <assert.h>
+#include <errno.h>
+
+#include <sys/types.h>
+#include <sys/sysmacros.h>
+#include <sys/debug.h>
+#include <sys/mman.h>
+#include <sys/vmm.h>
+#include <sys/vmm_dev.h>
+#include <vmmapi.h>
+
+#include "in_guest.h"
+
+#define	PAGE_SZ	4096
+
+#define	DIRTY_BITMAP_SZ	(MEM_TOTAL_SZ / (PAGE_SZ * 8))
+
+static void
+read_dirty_bitmap(struct vmctx *ctx, uint8_t *bitmap)
+{
+	struct vmm_dirty_tracker track = {
+		.vdt_start_gpa = 0,
+		.vdt_len = MEM_TOTAL_SZ,
+		.vdt_pfns = (void *)bitmap,
+	};
+	int err = ioctl(vm_get_device_fd(ctx), VM_TRACK_DIRTY_PAGES, &track);
+	if (err != 0) {
+		test_fail_errno(errno, "Could not get dirty page bitmap");
+	}
+}
+
+static uint8_t
+popc8(uint8_t val)
+{
+	uint8_t cnt;
+
+	for (cnt = 0; val != 0; val &= (val - 1)) {
+		cnt++;
+	}
+	return (cnt);
+}
+
+static uint_t
+count_dirty_pages(const uint8_t *bitmap)
+{
+	uint_t count = 0;
+	for (uint_t i = 0; i < DIRTY_BITMAP_SZ; i++) {
+		count += popc8(bitmap[i]);
+	}
+	return (count);
+}
+
+int
+main(int argc, char *argv[])
+{
+	const char *test_suite_name = basename(argv[0]);
+	struct vmctx *ctx = NULL;
+	int err;
+
+	ctx = test_initialize(test_suite_name);
+
+	/* Until #14251 is fixed, warn the user of the test requirement */
+	(void) fprintf(stderr,
+	    "Ensure that 'gpt_track_dirty' is set to 1 via mdb -kw\n"
+	    "The reasoning is described in illumos #14251\n");
+
+	err = test_setup_vcpu(ctx, 0, MEM_LOC_PAYLOAD, MEM_LOC_STACK);
+	if (err != 0) {
+		test_fail_errno(err, "Could not initialize vcpu0");
+	}
+
+	uint8_t dirty_bitmap[DIRTY_BITMAP_SZ] = { 0 };
+
+	/* Clear pages which were dirtied as part of initialization */
+	read_dirty_bitmap(ctx, dirty_bitmap);
+	if (count_dirty_pages(dirty_bitmap) == 0) {
+		test_fail_msg("no pages dirtied during setup\n");
+	}
+
+	/*
+	 * With nothing running, and the old dirty bits cleared, the NPT should
+	 * now be devoid of pages marked dirty.
+	 */
+	read_dirty_bitmap(ctx, dirty_bitmap);
+	if (count_dirty_pages(dirty_bitmap) != 0) {
+		test_fail_msg("pages still dirty after clear\n");
+	}
+
+	/* Dirty a page through the segvmm mapping. */
+	uint8_t *dptr = vm_map_gpa(ctx, MEM_LOC_STACK, 1);
+	*dptr = 1;
+
+	/* Check that it was marked as such */
+	read_dirty_bitmap(ctx, dirty_bitmap);
+	if (count_dirty_pages(dirty_bitmap) != 1) {
+		test_fail_msg("direct access did not dirty page\n");
+	}
+	if (dirty_bitmap[MEM_LOC_STACK / (PAGE_SZ * 8)] == 0) {
+		test_fail_msg("unexpected page dirtied\n");
+	}
+
+
+	/* Dirty it again to check shootdown logic */
+	*dptr = 2;
+	if (count_dirty_pages(dirty_bitmap) != 1) {
+		test_fail_msg("subsequent direct access did not dirty page\n");
+	}
+
+	struct vm_entry ventry = { 0 };
+	struct vm_exit vexit = { 0 };
+	do {
+		const enum vm_exit_kind kind =
+		    test_run_vcpu(ctx, 0, &ventry, &vexit);
+		switch (kind) {
+		case VEK_REENTR:
+			break;
+		case VEK_TEST_PASS:
+			/*
+			 * By now, the guest should have dirtied that page
+			 * directly via hardware-accelerated path.
+			 */
+			read_dirty_bitmap(ctx, dirty_bitmap);
+			/*
+			 * The guest will dirty more than the page it is
+			 * explicitly writing to: it must mark its own page
+			 * tables with accessed/dirty bits too.
+			 */
+			if (count_dirty_pages(dirty_bitmap) <= 1) {
+				test_fail_msg(
+				    "in-guest access did not dirty page\n");
+			}
+			if (dirty_bitmap[MEM_LOC_STACK / (PAGE_SZ * 8)] == 0) {
+				test_fail_msg("expected page not dirtied\n");
+			}
+			test_pass();
+			break;
+		default:
+			test_fail_vmexit(&vexit);
+			break;
+		}
+	} while (true);
+}
diff --git a/usr/src/test/bhyve-tests/tests/inst_emul/payload_page_dirty.s b/usr/src/test/bhyve-tests/tests/inst_emul/payload_page_dirty.s
new file mode 100644
index 0000000000..4c1869ca9b
--- /dev/null
+++ b/usr/src/test/bhyve-tests/tests/inst_emul/payload_page_dirty.s
@@ -0,0 +1,29 @@
+/*
+ * This file and its contents are supplied under the terms of the
+ * Common Development and Distribution License ("CDDL"), version 1.0.
+ * You may only use this file in accordance with the terms of version
+ * 1.0 of the CDDL.
+ *
+ * A full copy of the text of the CDDL should have accompanied this
+ * source.  A copy of the CDDL is also available via the Internet at
+ * http://www.illumos.org/license/CDDL.
+ */
+
+/*
+ * Copyright 2022 Oxide Computer Company
+ */
+
+#include <sys/asm_linkage.h>
+#include "payload_common.h"
+
+
+ENTRY(start)
+	/* Dirty the stack page once again */
+	xorl	%eax, %eax
+	movq	%rax, MEM_LOC_STACK
+
+	movw    $IOP_TEST_RESULT, %dx
+	movb    $TEST_RESULT_PASS, %al
+	outb    (%dx)
+	hlt
+SET_SIZE(start)