vhost+postcopy: Resolve client address

Resolve fault addresses read off the clients UFD into RAMBlock
and offset, and call back to the postcopy code to ask for the page.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 30 insertions, 1 deletions

diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
index b47de62c47..6dee1b565c 100644
--- a/hw/virtio/vhost-user.c
+++ b/hw/virtio/vhost-user.c
@@ -26,6 +26,7 @@
 #include <sys/socket.h>
 #include <sys/un.h>
 #include <linux/vhost.h>
+#include <linux/userfaultfd.h>
 
 #define VHOST_MEMORY_MAX_NREGIONS    8
 #define VHOST_USER_F_PROTOCOL_FEATURES 30
@@ -974,7 +975,35 @@ out:
 static int vhost_user_postcopy_fault_handler(struct PostCopyFD *pcfd,
                                              void *ufd)
 {
-    return 0;
+    struct vhost_dev *dev = pcfd->data;
+    struct vhost_user *u = dev->opaque;
+    struct uffd_msg *msg = ufd;
+    uint64_t faultaddr = msg->arg.pagefault.address;
+    RAMBlock *rb = NULL;
+    uint64_t rb_offset;
+    int i;
+
+    trace_vhost_user_postcopy_fault_handler(pcfd->idstr, faultaddr,
+                                            dev->mem->nregions);
+    for (i = 0; i < MIN(dev->mem->nregions, u->region_rb_len); i++) {
+        trace_vhost_user_postcopy_fault_handler_loop(i,
+                u->postcopy_client_bases[i], dev->mem->regions[i].memory_size);
+        if (faultaddr >= u->postcopy_client_bases[i]) {
+            /* Ofset of the fault address in the vhost region */
+            uint64_t region_offset = faultaddr - u->postcopy_client_bases[i];
+            if (region_offset < dev->mem->regions[i].memory_size) {
+                rb_offset = region_offset + u->region_rb_offset[i];
+                trace_vhost_user_postcopy_fault_handler_found(i,
+                        region_offset, rb_offset);
+                rb = u->region_rb[i];
+                return postcopy_request_shared_page(pcfd, rb, faultaddr,
+                                                    rb_offset);
+            }
+        }
+    }
+    error_report("%s: Failed to find region for fault %" PRIx64,
+                 __func__, faultaddr);
+    return -1;
 }
 
 /*