[Xen-devel] [PATCH 4/24] [xen-unstable.hg] make xenstored use grantref rather than map_foreign_range (which only privileged domains can do)

[Alex Zeffertt <alex.zeffertt@xxxxxxxxxxxxx>]

This patch modifies the xenstore daemon to use xc_gnttab_map_grant_ref
instead of xc_map_foreign_range where available.

TODO: This will probably break linking on Solaris, since they don't have
stubs for the gntmap functions yet.

A previous version of this patch was sent to xen-devel. See
http://lists.xensource.com/archives/html/xen-devel/2008-07/msg00610.html

Signed-off-by: Diego Ongaro <diego.ongaro@xxxxxxxxxx>
Signed-off-by: Alex Zeffertt <alex.zeffertt@xxxxxxxxxxxxx>
---

diff -r 289762278873 tools/xenstore/xenstored_domain.c
--- a/tools/xenstore/xenstored_domain.c Fri Aug 01 16:50:27 2008 +0100
+++ b/tools/xenstore/xenstored_domain.c Fri Aug 01 16:50:28 2008 +0100
@@ -31,8 +31,10 @@
 #include "xenstored_watch.h"
 
 #include <xenctrl.h>
+#include <xen/grant_table.h>
 
 static int *xc_handle;
+static int *xcg_handle;
 static evtchn_port_t virq_port;
 
 int xce_handle = -1; 
@@ -173,8 +175,12 @@
                        eprintf("> Unbinding port %i failed!\n", domain->port);
        }
 
-       if (domain->interface)
-               munmap(domain->interface, getpagesize());
+       if (domain->interface) {
+               if (*xcg_handle >= 0 && domain->domid != 0)
+                       xc_gnttab_munmap(*xcg_handle, domain->interface, 1);
+               else
+                       munmap(domain->interface, getpagesize());
+       }
 
        fire_watches(NULL, "@releaseDomain", false);
 
@@ -343,9 +349,17 @@
        domain = find_domain_by_domid(domid);
 
        if (domain == NULL) {
-               interface = xc_map_foreign_range(
-                       *xc_handle, domid,
-                       getpagesize(), PROT_READ|PROT_WRITE, mfn);
+               if (*xcg_handle >= 0) {
+                       /* this is the preferred method */
+                       interface = xc_gnttab_map_grant_ref(
+                               *xcg_handle, domid,
+                               GNTTAB_RESERVED_XENSTORE,
+                               PROT_READ|PROT_WRITE);
+               } else {
+                       interface = xc_map_foreign_range(
+                               *xc_handle, domid,
+                               getpagesize(), PROT_READ|PROT_WRITE, mfn);
+               }
                if (!interface) {
                        send_error(conn, errno);
                        return;
@@ -353,7 +367,10 @@
                /* Hang domain off "in" until we're finished. */
                domain = new_domain(in, domid, port);
                if (!domain) {
-                       munmap(interface, getpagesize());
+                       if (*xcg_handle >= 0)
+                               xc_gnttab_munmap(*xcg_handle, interface, 1);
+                       else
+                               munmap(interface, getpagesize());
                        send_error(conn, errno);
                        return;
                }
@@ -542,6 +559,12 @@
        return 0;
 }
 
+static int close_xcg_handle(void *_handle)
+{
+       xc_gnttab_close(*(int *)_handle);
+       return 0;
+}
+
 /* Returns the implicit path of a connection (only domains have this) */
 const char *get_implicit_path(const struct connection *conn)
 {
@@ -584,6 +607,7 @@
 {
        int rc;
 
+       /* Open the hypervisor interface. */
        xc_handle = talloc(talloc_autofree_context(), int);
        if (!xc_handle)
                barf_perror("Failed to allocate domain handle");
@@ -593,6 +617,17 @@
                barf_perror("Failed to open connection to hypervisor");
 
        talloc_set_destructor(xc_handle, close_xc_handle);
+
+       /* Open the gntdev interface. */
+       xcg_handle = talloc(talloc_autofree_context(), int);
+       if (!xcg_handle)
+               barf_perror("Failed to allocate domain gnttab handle");
+
+       *xcg_handle = xc_gnttab_open();
+       if (*xcg_handle < 0)
+               xprintf("WARNING: Failed to open connection to gnttab\n");
+       else
+               talloc_set_destructor(xcg_handle, close_xcg_handle);
 
        xce_handle = xc_evtchn_open();
 


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