tools/xenstored: add server feature support

Add per domain server features, which are initialized by the supported
features at domain introduction, or by live update from the migration
stream. This requires to add the DOMAIN_DATA record to the migration
stream, but for now it will only contain the feature word.

Advertise the Xenstore features to guests by setting the appropriate
bits in the ring page.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jason Andryuk <jason.andryuk@amd.com>

tools/xenstored/domain.c

@@ -32,6 +32,7 @@
 #include "transaction.h"
 #include "watch.h"
 #include "control.h"
+#include "lu.h"
 
 #include <xenevtchn.h>
 #include <xenmanage.h>
@@ -42,6 +43,8 @@
 #include <mini-os/xenbus.h>
 #endif
 
+#define XENSTORE_FEATURES	XENSTORE_SERVER_FEATURE_ERROR
+
 static xenmanage_handle *xm_handle;
 xengnttab_handle **xgt_handle;
 static evtchn_port_t virq_port;
@@ -115,6 +118,9 @@ struct domain
 	/* Event channel port */
 	evtchn_port_t port;
 
+	/* Server features supported for this domain. */
+	unsigned int features;
+
 	/* Domain path in store. */
 	char *path;
 
@@ -799,6 +805,7 @@ static struct domain *alloc_domain(const void *context, unsigned int domid,
 	domain->unique_id = unique_id;
 	domain->generation = generation;
 	domain->introduced = false;
+	domain->features = XENSTORE_FEATURES;
 
 	if (hashtable_add(domhash, &domain->domid, domain)) {
 		talloc_free(domain);
@@ -992,7 +999,8 @@ void ignore_connection(struct connection *conn, unsigned int err)
 {
 	trace("CONN %p ignored, reason %u\n", conn, err);
 
-	if (conn->domain && conn->domain->interface)
+	if (conn->domain && conn->domain->interface &&
+	    (conn->domain->features & XENSTORE_SERVER_FEATURE_ERROR))
 		conn->domain->interface->error = err;
 
 	conn->is_ignored = true;
@@ -1032,6 +1040,8 @@ static struct domain *introduce_domain(const void *ctx,
 			return NULL;
 		}
 		domain->interface = interface;
+		if (!restore)
+			interface->server_features = domain->features;
 
 		if (is_master_domain)
 			setup_structure(restore);
@@ -1849,6 +1859,54 @@ void read_state_connection(const void *ctx, const void *state)
 	}
 }
 
+static int dump_state_domain(const void *k, void *v, void *arg)
+{
+	struct domain *domain = v;
+	FILE *fp = arg;
+	struct xs_state_domain sd;
+	struct xs_state_record_header head;
+
+	head.type = XS_STATE_TYPE_DOMAIN;
+	head.length = sizeof(sd);
+	memset(&sd, 0, sizeof(sd));
+	sd.domain_id = domain->domid;
+
+	if (lu_status->version > 1)
+		sd.features = domain->features;
+
+	if (fwrite(&head, sizeof(head), 1, fp) != 1)
+		return 1;
+	if (fwrite(&sd, sizeof(sd), 1, fp) != 1)
+		return 1;
+	if (dump_state_align(fp))
+		return 1;
+
+	return 0;
+}
+
+const char *dump_state_domains(FILE *fp)
+{
+	const char *ret = NULL;
+
+	if (hashtable_iterate(domhash, dump_state_domain, fp))
+		ret = "Dump domain error";
+
+	return ret;
+}
+
+void read_state_domain(const void *ctx, const void *state, unsigned int version)
+{
+	const struct xs_state_domain *sd = state;
+	struct domain *domain;
+
+	domain = find_domain_struct(sd->domain_id);
+	if (!domain)
+		barf("referenced domain not found");
+
+	if (version > 1)
+		domain->features = sd->features;
+}
+
 struct domain_acc {
 	unsigned int domid;
 	int nodes;

tools/xenstored/domain.h

@@ -162,8 +162,11 @@ void wrl_apply_debit_direct(struct connection *conn);
 void wrl_apply_debit_trans_commit(struct connection *conn);
 
 const char *dump_state_connections(FILE *fp);
+const char *dump_state_domains(FILE *fp);
 
 void read_state_connection(const void *ctx, const void *state);
+void read_state_domain(const void *ctx, const void *state,
+		       unsigned int version);
 
 struct hashtable *domain_check_acc_init(void);
 void domain_check_acc_add(const struct node *node, struct hashtable *domains);

tools/xenstored/lu.c

@@ -21,6 +21,8 @@
 #include "lu.h"
 #include "watch.h"
 
+struct live_update *lu_status;
+
 #ifndef NO_LIVE_UPDATE
 
 struct lu_dump_state {
@@ -30,8 +32,6 @@ struct lu_dump_state {
 	char *filename;
 };
 
-struct live_update *lu_status;
-
 static int lu_destroy(void *data)
 {
 	lu_status = NULL;
@@ -128,6 +128,7 @@ void lu_read_state(void)
 	struct xs_state_record_header *head;
 	void *ctx = talloc_new(NULL); /* Work context for subfunctions. */
 	struct xs_state_preamble *pre;
+	unsigned int version;
 
 	syslog(LOG_INFO, "live-update: read state\n");
 	lu_get_dump_state(&state);
@@ -135,8 +136,9 @@ void lu_read_state(void)
 		barf_perror("No state found after live-update");
 
 	pre = state.buf;
+	version = be32toh(pre->version);
 	if (memcmp(pre->ident, XS_STATE_IDENT, sizeof(pre->ident)) ||
-	    !pre->version || be32toh(pre->version) > XS_STATE_VERSION ||
+	    !version || version > XS_STATE_VERSION ||
 	    pre->flags != XS_STATE_FLAGS)
 		barf("Unknown record identifier");
 	for (head = state.buf + sizeof(*pre);
@@ -159,6 +161,9 @@ void lu_read_state(void)
 		case XS_STATE_TYPE_NODE:
 			read_state_node(ctx, head + 1);
 			break;
+		case XS_STATE_TYPE_DOMAIN:
+			read_state_domain(ctx, head + 1, version);
+			break;
 		default:
 			xprintf("live-update: unknown state record %08x\n",
 				head->type);
@@ -297,6 +302,9 @@ static const char *lu_dump_state(const void *ctx, struct connection *conn)
 	if (ret)
 		goto out;
 	ret = dump_state_nodes(fp, ctx);
+	if (ret)
+		goto out;
+	ret = dump_state_domains(fp);
 	if (ret)
 		goto out;
 

tools/xenstored/lu.h

@@ -5,7 +5,6 @@
  * Copyright (C) 2022 Juergen Gross, SUSE LLC
  */
 
-#ifndef NO_LIVE_UPDATE
 struct live_update {
 	/* For verification the correct connection is acting. */
 	struct connection *conn;
@@ -32,6 +31,7 @@ struct live_update {
 
 extern struct live_update *lu_status;
 
+#ifndef NO_LIVE_UPDATE
 struct connection *lu_get_connection(void);
 bool lu_is_pending(void);
 void lu_read_state(void);