xen: Switch uses of xc_map_foreign_{pages,bulk} to use libxenforeignmemory API.

In Xen 4.7 we are refactoring parts libxenctrl into a number of
separate libraries which will provide backward and forward API and ABI
compatiblity.

One such library will be libxenforeignmemory which provides access to
privileged foreign mappings and which will provide an interface
equivalent to xc_map_foreign_{pages,bulk}.

The new xenforeignmemory_map() function behaves like
xc_map_foreign_pages() when the err argument is NULL and like
xc_map_foreign_bulk() when err is non-NULL, which maps into the shim
here onto checking err == NULL and calling the appropriate old
function.

Note that xenforeignmemory_map() takes the number of pages before the
arrays themselves, in order to support potentially future use of
variable-length-arrays in the prototype (in the future, when Xen's
baseline toolchain requirements are new enough to ensure VLAs are
supported).

In preparation for adding support for libxenforeignmemory add support
to the <=4.0 and <=4.6 compat code in xen_common.h to allow us to
switch to using the new API. These shims will disappear for versions
of Xen which include libxenforeignmemory.

Since libxenforeignmemory will have its own handle type but for <= 4.6
the functionality is provided by using a libxenctrl handle we
introduce a new global xen_fmem alongside the existing xen_xc. In fact
we make xen_fmem a pointer to the existing xen_xc, which then works
correctly with both <=4.0 (xc handle is an int) and <=4.6 (xc handle
is a pointer). In the latter case xen_fmem is actually a double
indirect pointer, but it all falls out in the wash.

Unlike libxenctrl libxenforeignmemory has an explicit unmap function,
rather than just specifying that munmap should be used, so the unmap
paths are updated to use xenforeignmemory_unmap, which is a shim for
munmap on these versions of xen. The mappings in xen-hvm.c do not
appear to be unmapped (which makes sense for a qemu-dm process)

In fb_disconnect this results in a change from simply mmap over the
existing mapping (with an implicit munmap) to expliclty unmapping with
xenforeignmemory_unmap and then mapping the required anonymous memory
in the same hole. I don't think this is a problem since any other
thread which was racily touching this region would already be running
the risk of hitting the mapping halfway through the call. If this is
thought to be a problem then we could consider adding an extra API to
the libxenforeignmemory interface to replace a foreign mapping with
anonymous shared memory, but I'd prefer not to.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Reviewed-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>

diff --git a/hw/char/xen_console.c b/hw/char/xen_console.c
index 3e8a57b4f7997bbce5d811194196281a78db99ec..b92d0c6dd2915bd4b00895511deee4b6407bdd90 100644 (file)
--- a/hw/char/xen_console.c
+++ b/hw/char/xen_console.c
@@ -229,9 +229,9 @@ static int con_initialise(struct XenDevice *xendev)
 
     if (!xendev->dev) {
         xen_pfn_t mfn = con->ring_ref;
-        con->sring = xc_map_foreign_pages(xen_xc, con->xendev.dom,
-                                         PROT_READ|PROT_WRITE,
-                                         &mfn, 1);
+        con->sring = xenforeignmemory_map(xen_fmem, con->xendev.dom,
+                                          PROT_READ|PROT_WRITE,
+                                          1, &mfn, NULL);
     } else {
         con->sring = xengnttab_map_grant_ref(xendev->gnttabdev, con->xendev.dom,
                                              con->ring_ref,
@@ -273,7 +273,7 @@ static void con_disconnect(struct XenDevice *xendev)
 
     if (con->sring) {
         if (!xendev->dev) {
-            munmap(con->sring, XC_PAGE_SIZE);
+            xenforeignmemory_unmap(xen_fmem, con->sring, 1);
         } else {
             xengnttab_unmap(xendev->gnttabdev, con->sring, 1);
         }

diff --git a/hw/display/xenfb.c b/hw/display/xenfb.c
index aa38803aa95d1cda0f8480f2471350aef36ad6c4..1676660e4e21ddce6938bf3ce7004c440f22a636 100644 (file)
--- a/hw/display/xenfb.c
+++ b/hw/display/xenfb.c
@@ -106,8 +106,8 @@ static int common_bind(struct common *c)
     if (xenstore_read_fe_int(&c->xendev, "event-channel", &c->xendev.remote_port) == -1)
        return -1;
 
-    c->page = xc_map_foreign_pages(xen_xc, c->xendev.dom,
-                                   PROT_READ | PROT_WRITE, &mfn, 1);
+    c->page = xenforeignmemory_map(xen_fmem, c->xendev.dom,
+                                   PROT_READ | PROT_WRITE, 1, &mfn, NULL);
     if (c->page == NULL)
        return -1;
 
@@ -122,7 +122,7 @@ static void common_unbind(struct common *c)
 {
     xen_be_unbind_evtchn(&c->xendev);
     if (c->page) {
-       munmap(c->page, XC_PAGE_SIZE);
+        xenforeignmemory_unmap(xen_fmem, c->page, 1);
        c->page = NULL;
     }
 }
@@ -495,15 +495,15 @@ static int xenfb_map_fb(struct XenFB *xenfb)
     fbmfns = g_malloc0(sizeof(xen_pfn_t) * xenfb->fbpages);
 
     xenfb_copy_mfns(mode, n_fbdirs, pgmfns, pd);
-    map = xc_map_foreign_pages(xen_xc, xenfb->c.xendev.dom,
-                              PROT_READ, pgmfns, n_fbdirs);
+    map = xenforeignmemory_map(xen_fmem, xenfb->c.xendev.dom,
+                               PROT_READ, n_fbdirs, pgmfns, NULL);
     if (map == NULL)
        goto out;
     xenfb_copy_mfns(mode, xenfb->fbpages, fbmfns, map);
-    munmap(map, n_fbdirs * XC_PAGE_SIZE);
+    xenforeignmemory_unmap(xen_fmem, map, n_fbdirs);
 
-    xenfb->pixels = xc_map_foreign_pages(xen_xc, xenfb->c.xendev.dom,
-            PROT_READ, fbmfns, xenfb->fbpages);
+    xenfb->pixels = xenforeignmemory_map(xen_fmem, xenfb->c.xendev.dom,
+            PROT_READ, xenfb->fbpages, fbmfns, NULL);
     if (xenfb->pixels == NULL)
        goto out;
 
@@ -913,6 +913,7 @@ static void fb_disconnect(struct XenDevice *xendev)
      *   Replacing the framebuffer with anonymous shared memory
      *   instead.  This releases the guest pages and keeps qemu happy.
      */
+    xenforeignmemory_unmap(xen_fmem, fb->pixels, fb->fbpages);
     fb->pixels = mmap(fb->pixels, fb->fbpages * XC_PAGE_SIZE,
                       PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANON,
                       -1, 0);

diff --git a/hw/xen/xen_backend.c b/hw/xen/xen_backend.c
index 966e34f3cb7228d3ea1f08125d639c6a57433f04..caa459ca3ea64275bf23aa296184a9e4e38eac80 100644 (file)
--- a/hw/xen/xen_backend.c
+++ b/hw/xen/xen_backend.c
@@ -45,6 +45,7 @@
 
 /* public */
 XenXC xen_xc = XC_HANDLER_INITIAL_VALUE;
+xenforeignmemory_handle *xen_fmem = NULL;
 struct xs_handle *xenstore = NULL;
 const char *xen_protocol;
 
@@ -717,7 +718,7 @@ int xen_be_init(void)
 
     qemu_set_fd_handler(xs_fileno(xenstore), xenstore_update, NULL, NULL);
 
-    if (xen_xc == XC_HANDLER_INITIAL_VALUE) {
+    if (xen_xc == XC_HANDLER_INITIAL_VALUE || xen_fmem == NULL) {
         /* Check if xen_init() have been called */
         goto err;
     }

diff --git a/include/hw/xen/xen_backend.h b/include/hw/xen/xen_backend.h
index 8e8857b1550a74652db04d97b9b924daa28afc53..e0d52ee44f0c2a67c9267e29c90e9eb8b2b92281 100644 (file)
--- a/include/hw/xen/xen_backend.h
+++ b/include/hw/xen/xen_backend.h
@@ -57,6 +57,7 @@ struct XenDevice {
 
 /* variables */
 extern XenXC xen_xc;
+extern xenforeignmemory_handle *xen_fmem;
 extern struct xs_handle *xenstore;
 extern const char *xen_protocol;
 

diff --git a/include/hw/xen/xen_common.h b/include/hw/xen/xen_common.h
index 8f38310426801fc74aace436901b18e7613693bd..95275b34c43aa385446a5507f2e243b56e12a9de 100644 (file)
--- a/include/hw/xen/xen_common.h
+++ b/include/hw/xen/xen_common.h
@@ -41,6 +41,7 @@ static inline void *xc_map_foreign_bulk(int xc_handle, uint32_t dom, int prot,
 typedef int XenXC;
 typedef int xenevtchn_handle;
 typedef int xengnttab_handle;
+typedef int xenforeignmemory_handle;
 
 #  define XC_INTERFACE_FMT "%i"
 #  define XC_HANDLER_INITIAL_VALUE    -1
@@ -104,6 +105,8 @@ static inline XenXC xen_xc_interface_open(void *logger, void *dombuild_logger,
     return xc_interface_open();
 }
 
+/* See below for xenforeignmemory_* APIs */
+
 static inline int xc_fd(int xen_xc)
 {
     return xen_xc;
@@ -149,6 +152,7 @@ static inline void xs_close(struct xs_handle *xsh)
 #else
 
 typedef xc_interface *XenXC;
+typedef xc_interface *xenforeignmemory_handle;
 typedef xc_evtchn xenevtchn_handle;
 typedef xc_gnttab xengnttab_handle;
 
@@ -178,6 +182,8 @@ static inline XenXC xen_xc_interface_open(void *logger, void *dombuild_logger,
     return xc_interface_open(logger, dombuild_logger, open_flags);
 }
 
+/* See below for xenforeignmemory_* APIs */
+
 /* FIXME There is now way to have the xen fd */
 static inline int xc_fd(xc_interface *xen_xc)
 {
@@ -501,4 +507,23 @@ static inline int xen_domain_create(XenXC xc, uint32_t ssidref,
 }
 #endif
 
+#if CONFIG_XEN_CTRL_INTERFACE_VERSION < 471
+
+#define xenforeignmemory_open(l, f) &xen_xc
+
+static inline void *xenforeignmemory_map(XenXC *h, uint32_t dom,
+                                         int prot, size_t pages,
+                                         const xen_pfn_t arr[/*pages*/],
+                                         int err[/*pages*/])
+{
+    if (err)
+        return xc_map_foreign_bulk(*h, dom, prot, arr, err, pages);
+    else
+        return xc_map_foreign_pages(*h, dom, prot, arr, pages);
+}
+
+#define xenforeignmemory_unmap(h, p, s) munmap(p, s * XC_PAGE_SIZE)
+
+#endif
+
 #endif /* QEMU_HW_XEN_COMMON_H */

diff --git a/xen-common.c b/xen-common.c
index 0dcdbc39f473e0e690b4a18f993b690e853e5e89..6cd2959e21695b7042bb1d1cc1eb30e04193020b 100644 (file)
--- a/xen-common.c
+++ b/xen-common.c
@@ -118,6 +118,12 @@ static int xen_init(MachineState *ms)
         xen_be_printf(NULL, 0, "can't open xen interface\n");
         return -1;
     }
+    xen_fmem = xenforeignmemory_open(0, 0);
+    if (xen_fmem == NULL) {
+        xen_be_printf(NULL, 0, "can't open xen fmem interface\n");
+        xc_interface_close(xen_xc);
+        return -1;
+    }
     qemu_add_vm_change_state_handler(xen_change_state_handler, NULL);
 
     global_state_set_optional();

diff --git a/xen-hvm.c b/xen-hvm.c
index 878ae0a03d84d620e4cd1bb5eacce3bfeb342776..590f66dcf8bb2bfd19fccaf203ef3323c4416524 100644 (file)
--- a/xen-hvm.c
+++ b/xen-hvm.c
@@ -1242,9 +1242,9 @@ void xen_hvm_init(PCMachineState *pcms, MemoryRegion **ram_memory)
     DPRINTF("buffered io page at pfn %lx\n", bufioreq_pfn);
     DPRINTF("buffered io evtchn is %x\n", bufioreq_evtchn);
 
-    state->shared_page = xc_map_foreign_pages(xen_xc, xen_domid,
+    state->shared_page = xenforeignmemory_map(xen_fmem, xen_domid,
                                               PROT_READ|PROT_WRITE,
-                                              &ioreq_pfn, 1);
+                                              1, &ioreq_pfn, NULL);
     if (state->shared_page == NULL) {
         error_report("map shared IO page returned error %d handle=" XC_INTERFACE_FMT,
                      errno, xen_xc);
@@ -1255,8 +1255,8 @@ void xen_hvm_init(PCMachineState *pcms, MemoryRegion **ram_memory)
     if (!rc) {
         DPRINTF("shared vmport page at pfn %lx\n", ioreq_pfn);
         state->shared_vmport_page =
-            xc_map_foreign_pages(xen_xc, xen_domid, PROT_READ|PROT_WRITE,
-                                 &ioreq_pfn, 1);
+            xenforeignmemory_map(xen_fmem, xen_domid, PROT_READ|PROT_WRITE,
+                                 1, &ioreq_pfn, NULL);
         if (state->shared_vmport_page == NULL) {
             error_report("map shared vmport IO page returned error %d handle="
                          XC_INTERFACE_FMT, errno, xen_xc);
@@ -1268,9 +1268,9 @@ void xen_hvm_init(PCMachineState *pcms, MemoryRegion **ram_memory)
         goto err;
     }
 
-    state->buffered_io_page = xc_map_foreign_pages(xen_xc, xen_domid,
+    state->buffered_io_page = xenforeignmemory_map(xen_fmem, xen_domid,
                                                    PROT_READ|PROT_WRITE,
-                                                   &bufioreq_pfn, 1);
+                                                   1, &bufioreq_pfn, NULL);
     if (state->buffered_io_page == NULL) {
         error_report("map buffered IO page returned error %d", errno);
         goto err;

diff --git a/xen-mapcache.c b/xen-mapcache.c
index 97fece23587ac0c0816299bb781e03c4d975c2d2..4a043780200e743d8d816b10647b294fa08cd7f4 100644 (file)
--- a/xen-mapcache.c
+++ b/xen-mapcache.c
@@ -176,10 +176,10 @@ static void xen_remap_bucket(MapCacheEntry *entry,
         pfns[i] = (address_index << (MCACHE_BUCKET_SHIFT-XC_PAGE_SHIFT)) + i;
     }
 
-    vaddr_base = xc_map_foreign_bulk(xen_xc, xen_domid, PROT_READ|PROT_WRITE,
-                                     pfns, err, nb_pfn);
+    vaddr_base = xenforeignmemory_map(xen_fmem, xen_domid, PROT_READ|PROT_WRITE,
+                                      nb_pfn, pfns, err);
     if (vaddr_base == NULL) {
-        perror("xc_map_foreign_bulk");
+        perror("xenforeignmemory_map");
         exit(-1);
     }