xenconsoled: use grant references instead of map_foreign_range

Grant references for the xenstore and xenconsole shared pages exist, but
currently only xenstore uses these references.  Change the xenconsole
daemon to prefer using the grant reference over map_foreign_range when
mapping the shared console ring.

This allows xenconsoled to be run in a domain other than dom0 if set up
correctly - for libxl, the xenstore path /tool/xenconsoled/domid
specifies the domain containing xenconsoled.

Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Committed-by: Ian Campbell <ian.campbell@citrix.com>

3 files changed, 42 insertions, 10 deletions

diff --git a/tools/console/daemon/io.c b/tools/console/daemon/io.c
index 6b659d4419..176ac3cc53 100644
--- a/tools/console/daemon/io.c
+++ b/tools/console/daemon/io.c
@@ -24,6 +24,7 @@
 #include "io.h"
 #include <xenstore.h>
 #include <xen/io/console.h>
+#include <xen/grant_table.h>
 
 #include <stdlib.h>
 #include <errno.h>
@@ -67,6 +68,8 @@ static int log_time_hv_needts = 1;
 static int log_time_guest_needts = 1;
 static int log_hv_fd = -1;
 
+static xc_gnttab *xcg_handle = NULL;
+
 static struct pollfd  *fds;
 static unsigned int current_array_size;
 static unsigned int nr_fds;
@@ -506,6 +509,18 @@ static int xs_gather(struct xs_handle *xs, const char *dir, ...)
 	va_end(ap);
 	return ret;
 }
+
+static void domain_unmap_interface(struct domain *dom)
+{
+	if (dom->interface == NULL)
+		return;
+	if (xcg_handle && dom->ring_ref == -1)
+		xc_gnttab_munmap(xcg_handle, dom->interface, 1);
+	else
+		munmap(dom->interface, getpagesize());
+	dom->interface = NULL;
+	dom->ring_ref = -1;
+}
  
 static int domain_create_ring(struct domain *dom)
 {
@@ -527,9 +542,19 @@ static int domain_create_ring(struct domain *dom)
 	}
 	free(type);
 
-	if (ring_ref != dom->ring_ref) {
-		if (dom->interface != NULL)
-			munmap(dom->interface, getpagesize());
+	/* If using ring_ref and it has changed, remap */
+	if (ring_ref != dom->ring_ref && dom->ring_ref != -1)
+		domain_unmap_interface(dom);
+
+	if (!dom->interface && xcg_handle) {
+		/* Prefer using grant table */
+		dom->interface = xc_gnttab_map_grant_ref(xcg_handle,
+			dom->domid, GNTTAB_RESERVED_CONSOLE,
+			PROT_READ|PROT_WRITE);
+		dom->ring_ref = -1;
+	}
+	if (!dom->interface) {
+		/* Fall back to xc_map_foreign_range */
 		dom->interface = xc_map_foreign_range(
 			xc, dom->domid, getpagesize(),
 			PROT_READ|PROT_WRITE,
@@ -725,9 +750,7 @@ static void shutdown_domain(struct domain *d)
 {
 	d->is_dead = true;
 	watch_domain(d, false);
-	if (d->interface != NULL)
-		munmap(d->interface, getpagesize());
-	d->interface = NULL;
+	domain_unmap_interface(d);
 	if (d->xce_handle != NULL)
 		xc_evtchn_close(d->xce_handle);
 	d->xce_handle = NULL;
@@ -735,7 +758,7 @@ static void shutdown_domain(struct domain *d)
 
 static unsigned enum_pass = 0;
 
-void enum_domains(void)
+static void enum_domains(void)
 {
 	int domid = 1;
 	xc_dominfo_t dominfo;
@@ -996,6 +1019,14 @@ void handle_io(void)
 		}
 	}
 
+	xcg_handle = xc_gnttab_open(NULL, 0);
+	if (xcg_handle == NULL) {
+		dolog(LOG_DEBUG, "Failed to open xcg handle: %d (%s)",
+		      errno, strerror(errno));
+	}
+
+	enum_domains();
+
 	for (;;) {
 		struct domain *d, *n;
 		int poll_timeout; /* timeout in milliseconds */
@@ -1165,6 +1196,10 @@ void handle_io(void)
 		xc_evtchn_close(xce_handle);
 		xce_handle = NULL;
 	}
+	if (xcg_handle != NULL) {
+		xc_gnttab_close(xcg_handle);
+		xcg_handle = NULL;
+	}
 	log_hv_evtchn = -1;
 }
 
diff --git a/tools/console/daemon/io.h b/tools/console/daemon/io.h
index 8fa04b6775..f658bfcea0 100644
--- a/tools/console/daemon/io.h
+++ b/tools/console/daemon/io.h
@@ -21,7 +21,6 @@
 #ifndef CONSOLED_IO_H
 #define CONSOLED_IO_H
 
-void enum_domains(void);
 void handle_io(void);
 
 #endif
diff --git a/tools/console/daemon/main.c b/tools/console/daemon/main.c
index 789baa6c23..92d2fc4123 100644
--- a/tools/console/daemon/main.c
+++ b/tools/console/daemon/main.c
@@ -161,8 +161,6 @@ int main(int argc, char **argv)
 	if (!xen_setup())
 		exit(1);
 
-	enum_domains();
-
 	handle_io();
 
 	closelog();