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qemu/tests/unit/test-xs-node.c
David Woodhouse 7248b87cb0 hw/xen: Implement XenStore transactions 
Given that the whole thing supported copy on write from the beginning,
transactions end up being fairly simple. On starting a transaction, just
take a ref of the existing root; swap it back in on a successful commit.

The main tree has a transaction ID too, and we keep a record of the last
transaction ID given out. if the main tree is ever modified when it isn't
the latest, it gets a new transaction ID.

A commit can only succeed if the main tree hasn't moved on since it was
forked. Strictly speaking, the XenStore protocol allows a transaction to
succeed as long as nothing *it* read or wrote has changed in the interim,
but no implementations do that; *any* change is sufficient to abort a
transaction.

This does not yet fire watches on the changed nodes on a commit. That bit
is more fun and will come in a follow-on commit.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Paul Durrant <paul@xen.org>
2023-03-07 17:04:30 +00:00

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/*
* QEMU XenStore XsNode testing
*
* Copyright © 2023 Amazon.com, Inc. or its affiliates. All Rights Reserved.
* This work is licensed under the terms of the GNU GPL, version 2 or later.
* See the COPYING file in the top-level directory.
*/
#include "qemu/osdep.h"
#include "qapi/error.h"
#include "qemu/module.h"
static int nr_xs_nodes;
static GList *xs_node_list;
#define XS_NODE_UNIT_TEST
/*
* We don't need the core Xen definitions. And we *do* want to be able
* to run the unit tests even on architectures that Xen doesn't support
* (because life's too short to bother doing otherwise, and test coverage
* doesn't hurt).
*/
#define __XEN_PUBLIC_XEN_H__
#include "hw/i386/kvm/xenstore_impl.c"
#define DOMID_QEMU 0
#define DOMID_GUEST 1
/* This doesn't happen in qemu but we want to make valgrind happy */
static void xs_impl_delete(XenstoreImplState *s)
{
int err;
xs_impl_reset_watches(s, DOMID_GUEST);
g_assert(!s->nr_domu_watches);
err = xs_impl_rm(s, DOMID_QEMU, XBT_NULL, "/local");
g_assert(!err);
g_assert(s->nr_nodes == 1);
g_hash_table_unref(s->watches);
g_hash_table_unref(s->transactions);
xs_node_unref(s->root);
g_free(s);
if (xs_node_list) {
GList *l;
for (l = xs_node_list; l; l = l->next) {
XsNode *n = l->data;
printf("Remaining node at %p name %s ref %u\n", n, n->name,
n->ref);
}
}
g_assert(!nr_xs_nodes);
}
static int write_str(XenstoreImplState *s, unsigned int dom_id,
unsigned int tx_id, const char *path,
const char *content)
{
GByteArray *d = g_byte_array_new();
int err;
g_byte_array_append(d, (void *)content, strlen(content));
err = xs_impl_write(s, dom_id, tx_id, path, d);
g_byte_array_unref(d);
return err;
}
static void watch_cb(void *_str, const char *path, const char *token)
{
GString *str = _str;
g_string_append(str, path);
g_string_append(str, token);
}
static XenstoreImplState *setup(void)
{
XenstoreImplState *s = xs_impl_create();
char *abspath;
int err;
abspath = g_strdup_printf("/local/domain/%u", DOMID_GUEST);
err = write_str(s, DOMID_QEMU, XBT_NULL, abspath, "");
g_assert(!err);
g_assert(s->nr_nodes == 4);
g_free(abspath);
abspath = g_strdup_printf("/local/domain/%u/some", DOMID_GUEST);
err = write_str(s, DOMID_QEMU, XBT_NULL, abspath, "");
g_assert(!err);
g_assert(s->nr_nodes == 5);
g_free(abspath);
return s;
}
static void test_xs_node_simple(void)
{
GByteArray *data = g_byte_array_new();
XenstoreImplState *s = setup();
GString *guest_watches = g_string_new(NULL);
GString *qemu_watches = g_string_new(NULL);
GList *items = NULL;
XsNode *old_root;
uint64_t gencnt;
int err;
g_assert(s);
err = xs_impl_watch(s, DOMID_GUEST, "some", "guestwatch",
watch_cb, guest_watches);
g_assert(!err);
g_assert(guest_watches->len == strlen("someguestwatch"));
g_assert(!strcmp(guest_watches->str, "someguestwatch"));
g_string_truncate(guest_watches, 0);
err = xs_impl_watch(s, 0, "/local/domain/1/some", "qemuwatch",
watch_cb, qemu_watches);
g_assert(!err);
g_assert(qemu_watches->len == strlen("/local/domain/1/someqemuwatch"));
g_assert(!strcmp(qemu_watches->str, "/local/domain/1/someqemuwatch"));
g_string_truncate(qemu_watches, 0);
/* Read gives ENOENT when it should */
err = xs_impl_read(s, DOMID_GUEST, XBT_NULL, "foo", data);
g_assert(err == ENOENT);
/* Write works */
err = write_str(s, DOMID_GUEST, XBT_NULL, "some/relative/path",
"something");
g_assert(s->nr_nodes == 7);
g_assert(!err);
g_assert(!strcmp(guest_watches->str,
"some/relative/pathguestwatch"));
g_assert(!strcmp(qemu_watches->str,
"/local/domain/1/some/relative/pathqemuwatch"));
g_string_truncate(qemu_watches, 0);
g_string_truncate(guest_watches, 0);
xs_impl_reset_watches(s, 0);
/* Read gives back what we wrote */
err = xs_impl_read(s, DOMID_GUEST, XBT_NULL, "some/relative/path", data);
g_assert(!err);
g_assert(data->len == strlen("something"));
g_assert(!memcmp(data->data, "something", data->len));
/* Even if we use an abolute path */
g_byte_array_set_size(data, 0);
err = xs_impl_read(s, DOMID_GUEST, XBT_NULL,
"/local/domain/1/some/relative/path", data);
g_assert(!err);
g_assert(data->len == strlen("something"));
g_assert(!qemu_watches->len);
g_assert(!guest_watches->len);
/* Keep a copy, to force COW mode */
old_root = xs_node_ref(s->root);
/* Write works again */
err = write_str(s, DOMID_GUEST, XBT_NULL,
"/local/domain/1/some/relative/path2",
"something else");
g_assert(!err);
g_assert(s->nr_nodes == 8);
g_assert(!qemu_watches->len);
g_assert(!strcmp(guest_watches->str, "some/relative/path2guestwatch"));
g_string_truncate(guest_watches, 0);
/* Overwrite an existing node */
err = write_str(s, DOMID_GUEST, XBT_NULL, "some/relative/path",
"another thing");
g_assert(!err);
g_assert(s->nr_nodes == 8);
g_assert(!qemu_watches->len);
g_assert(!strcmp(guest_watches->str, "some/relative/pathguestwatch"));
g_string_truncate(guest_watches, 0);
/* We can list the two files we wrote */
err = xs_impl_directory(s, DOMID_GUEST, XBT_NULL, "some/relative", &gencnt,
&items);
g_assert(!err);
g_assert(items);
g_assert(gencnt == 2);
g_assert(!strcmp(items->data, "path"));
g_assert(items->next);
g_assert(!strcmp(items->next->data, "path2"));
g_assert(!items->next->next);
g_list_free_full(items, g_free);
err = xs_impl_unwatch(s, DOMID_GUEST, "some", "guestwatch",
watch_cb, guest_watches);
g_assert(!err);
err = xs_impl_unwatch(s, DOMID_GUEST, "some", "guestwatch",
watch_cb, guest_watches);
g_assert(err == ENOENT);
err = xs_impl_watch(s, DOMID_GUEST, "some/relative/path2", "watchp2",
watch_cb, guest_watches);
g_assert(!err);
g_assert(guest_watches->len == strlen("some/relative/path2watchp2"));
g_assert(!strcmp(guest_watches->str, "some/relative/path2watchp2"));
g_string_truncate(guest_watches, 0);
err = xs_impl_watch(s, DOMID_GUEST, "/local/domain/1/some/relative",
"watchrel", watch_cb, guest_watches);
g_assert(!err);
g_assert(guest_watches->len ==
strlen("/local/domain/1/some/relativewatchrel"));
g_assert(!strcmp(guest_watches->str,
"/local/domain/1/some/relativewatchrel"));
g_string_truncate(guest_watches, 0);
/* Write somewhere else which already existed */
err = write_str(s, DOMID_GUEST, XBT_NULL, "some/relative", "moredata");
g_assert(!err);
g_assert(s->nr_nodes == 8);
g_assert(!strcmp(guest_watches->str,
"/local/domain/1/some/relativewatchrel"));
g_string_truncate(guest_watches, 0);
g_byte_array_set_size(data, 0);
err = xs_impl_read(s, DOMID_GUEST, XBT_NULL, "some/relative", data);
g_assert(!err);
g_assert(data->len == strlen("moredata"));
g_assert(!memcmp(data->data, "moredata", data->len));
/* Overwrite existing data */
err = write_str(s, DOMID_GUEST, XBT_NULL, "some/relative", "otherdata");
g_assert(!err);
g_string_truncate(guest_watches, 0);
g_byte_array_set_size(data, 0);
err = xs_impl_read(s, DOMID_GUEST, XBT_NULL, "some/relative", data);
g_assert(!err);
g_assert(data->len == strlen("otherdata"));
g_assert(!memcmp(data->data, "otherdata", data->len));
/* Remove the subtree */
err = xs_impl_rm(s, DOMID_GUEST, XBT_NULL, "some/relative");
g_assert(!err);
g_assert(s->nr_nodes == 5);
/* Each watch fires with the least specific relevant path */
g_assert(strstr(guest_watches->str,
"some/relative/path2watchp2"));
g_assert(strstr(guest_watches->str,
"/local/domain/1/some/relativewatchrel"));
g_string_truncate(guest_watches, 0);
g_byte_array_set_size(data, 0);
err = xs_impl_read(s, DOMID_GUEST, XBT_NULL, "some/relative", data);
g_assert(err == ENOENT);
g_byte_array_unref(data);
xs_impl_reset_watches(s, DOMID_GUEST);
g_string_free(qemu_watches, true);
g_string_free(guest_watches, true);
xs_node_unref(old_root);
xs_impl_delete(s);
}
static void do_test_xs_node_tx(bool fail, bool commit)
{
XenstoreImplState *s = setup();
GString *watches = g_string_new(NULL);
GByteArray *data = g_byte_array_new();
unsigned int tx_id = XBT_NULL;
int err;
g_assert(s);
/* Set a watch */
err = xs_impl_watch(s, DOMID_GUEST, "some", "watch",
watch_cb, watches);
g_assert(!err);
g_assert(watches->len == strlen("somewatch"));
g_assert(!strcmp(watches->str, "somewatch"));
g_string_truncate(watches, 0);
/* Write something */
err = write_str(s, DOMID_GUEST, XBT_NULL, "some/relative/path",
"something");
g_assert(s->nr_nodes == 7);
g_assert(!err);
g_assert(!strcmp(watches->str,
"some/relative/pathwatch"));
g_string_truncate(watches, 0);
/* Create a transaction */
err = xs_impl_transaction_start(s, DOMID_GUEST, &tx_id);
g_assert(!err);
if (fail) {
/* Write something else in the root */
err = write_str(s, DOMID_GUEST, XBT_NULL, "some/relative/path",
"another thing");
g_assert(!err);
g_assert(s->nr_nodes == 7);
g_assert(!strcmp(watches->str,
"some/relative/pathwatch"));
g_string_truncate(watches, 0);
}
g_assert(!watches->len);
/* Perform a write in the transaction */
err = write_str(s, DOMID_GUEST, tx_id, "some/relative/path",
"something else");
g_assert(!err);
g_assert(s->nr_nodes == 7);
g_assert(!watches->len);
err = xs_impl_read(s, DOMID_GUEST, XBT_NULL, "some/relative/path", data);
g_assert(!err);
if (fail) {
g_assert(data->len == strlen("another thing"));
g_assert(!memcmp(data->data, "another thing", data->len));
} else {
g_assert(data->len == strlen("something"));
g_assert(!memcmp(data->data, "something", data->len));
}
g_byte_array_set_size(data, 0);
err = xs_impl_read(s, DOMID_GUEST, tx_id, "some/relative/path", data);
g_assert(!err);
g_assert(data->len == strlen("something else"));
g_assert(!memcmp(data->data, "something else", data->len));
g_byte_array_set_size(data, 0);
/* Attempt to commit the transaction */
err = xs_impl_transaction_end(s, DOMID_GUEST, tx_id, commit);
if (commit && fail) {
g_assert(err == EAGAIN);
} else {
g_assert(!err);
}
g_assert(!watches->len);
g_assert(s->nr_nodes == 7);
err = xs_impl_unwatch(s, DOMID_GUEST, "some", "watch",
watch_cb, watches);
g_assert(!err);
err = xs_impl_read(s, DOMID_GUEST, XBT_NULL, "some/relative/path", data);
g_assert(!err);
if (fail) {
g_assert(data->len == strlen("another thing"));
g_assert(!memcmp(data->data, "another thing", data->len));
} else if (commit) {
g_assert(data->len == strlen("something else"));
g_assert(!memcmp(data->data, "something else", data->len));
} else {
g_assert(data->len == strlen("something"));
g_assert(!memcmp(data->data, "something", data->len));
}
g_byte_array_unref(data);
g_string_free(watches, true);
xs_impl_delete(s);
}
static void test_xs_node_tx_fail(void)
{
do_test_xs_node_tx(true, true);
}
static void test_xs_node_tx_abort(void)
{
do_test_xs_node_tx(false, false);
do_test_xs_node_tx(true, false);
}
static void test_xs_node_tx_succeed(void)
{
do_test_xs_node_tx(false, true);
}
int main(int argc, char **argv)
{
g_test_init(&argc, &argv, NULL);
module_call_init(MODULE_INIT_QOM);
g_test_add_func("/xs_node/simple", test_xs_node_simple);
g_test_add_func("/xs_node/tx_abort", test_xs_node_tx_abort);
g_test_add_func("/xs_node/tx_fail", test_xs_node_tx_fail);
g_test_add_func("/xs_node/tx_succeed", test_xs_node_tx_succeed);
return g_test_run();
}
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