xen-hvm: try to use xenforeignmemory_map_resource() to map ioreq pages

Xen 4.11 has a new API to directly map guest resources. Among the resources
that can be mapped using this API are ioreq pages.

This patch modifies QEMU to attempt to use the new API should it exist,
falling back to the previous mechanism if it is unavailable.

Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
Reviewed-by: Anthony PERARD <anthony.perard@citrix.com>
Signed-off-by: Stefano Stabellini <sstabellini@kernel.org>

1 files changed, 51 insertions, 15 deletions

diff --git a/hw/i386/xen/xen-hvm.c b/hw/i386/xen/xen-hvm.c
index 2afab6573b..54f99abfea 100644
--- a/hw/i386/xen/xen-hvm.c
+++ b/hw/i386/xen/xen-hvm.c
@@ -1237,13 +1237,39 @@ static void xen_wakeup_notifier(Notifier *notifier, void *data)
 
 static int xen_map_ioreq_server(XenIOState *state)
 {
+    void *addr = NULL;
+    xenforeignmemory_resource_handle *fres;
     xen_pfn_t ioreq_pfn;
     xen_pfn_t bufioreq_pfn;
     evtchn_port_t bufioreq_evtchn;
     int rc;
 
+    /*
+     * Attempt to map using the resource API and fall back to normal
+     * foreign mapping if this is not supported.
+     */
+    QEMU_BUILD_BUG_ON(XENMEM_resource_ioreq_server_frame_bufioreq != 0);
+    QEMU_BUILD_BUG_ON(XENMEM_resource_ioreq_server_frame_ioreq(0) != 1);
+    fres = xenforeignmemory_map_resource(xen_fmem, xen_domid,
+                                         XENMEM_resource_ioreq_server,
+                                         state->ioservid, 0, 2,
+                                         &addr,
+                                         PROT_READ | PROT_WRITE, 0);
+    if (fres != NULL) {
+        trace_xen_map_resource_ioreq(state->ioservid, addr);
+        state->buffered_io_page = addr;
+        state->shared_page = addr + TARGET_PAGE_SIZE;
+    } else if (errno != EOPNOTSUPP) {
+        error_report("failed to map ioreq server resources: error %d handle=%p",
+                     errno, xen_xc);
+        return -1;
+    }
+
     rc = xen_get_ioreq_server_info(xen_domid, state->ioservid,
-                                   &ioreq_pfn, &bufioreq_pfn,
+                                   (state->shared_page == NULL) ?
+                                   &ioreq_pfn : NULL,
+                                   (state->buffered_io_page == NULL) ?
+                                   &bufioreq_pfn : NULL,
                                    &bufioreq_evtchn);
     if (rc < 0) {
         error_report("failed to get ioreq server info: error %d handle=%p",
@@ -1251,27 +1277,37 @@ static int xen_map_ioreq_server(XenIOState *state)
         return rc;
     }
 
-    DPRINTF("shared page at pfn %lx\n", ioreq_pfn);
-    DPRINTF("buffered io page at pfn %lx\n", bufioreq_pfn);
-    DPRINTF("buffered io evtchn is %x\n", bufioreq_evtchn);
-
-    state->shared_page = xenforeignmemory_map(xen_fmem, xen_domid,
-                                              PROT_READ | PROT_WRITE,
-                                              1, &ioreq_pfn, NULL);
     if (state->shared_page == NULL) {
-        error_report("map shared IO page returned error %d handle=%p",
-                     errno, xen_xc);
-        return -1;
+        DPRINTF("shared page at pfn %lx\n", ioreq_pfn);
+
+        state->shared_page = xenforeignmemory_map(xen_fmem, xen_domid,
+                                                  PROT_READ | PROT_WRITE,
+                                                  1, &ioreq_pfn, NULL);
+        if (state->shared_page == NULL) {
+            error_report("map shared IO page returned error %d handle=%p",
+                         errno, xen_xc);
+        }
     }
 
-    state->buffered_io_page = xenforeignmemory_map(xen_fmem, xen_domid,
-                                                   PROT_READ | PROT_WRITE,
-                                                   1, &bufioreq_pfn, NULL);
     if (state->buffered_io_page == NULL) {
-        error_report("map buffered IO page returned error %d", errno);
+        DPRINTF("buffered io page at pfn %lx\n", bufioreq_pfn);
+
+        state->buffered_io_page = xenforeignmemory_map(xen_fmem, xen_domid,
+                                                       PROT_READ | PROT_WRITE,
+                                                       1, &bufioreq_pfn,
+                                                       NULL);
+        if (state->buffered_io_page == NULL) {
+            error_report("map buffered IO page returned error %d", errno);
+            return -1;
+        }
+    }
+
+    if (state->shared_page == NULL || state->buffered_io_page == NULL) {
         return -1;
     }
 
+    DPRINTF("buffered io evtchn is %x\n", bufioreq_evtchn);
+
     state->bufioreq_remote_port = bufioreq_evtchn;
 
     return 0;