[Qemu-devel] [PATCH v6 14/29] libvhost-user+postcopy: Register new regions with the ufd

["Dr. David Alan Gilbert (git)" <dgilbert@redhat.com>]

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

When new regions are sent to the client using SET_MEM_TABLE, register
them with the userfaultfd.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
---
 contrib/libvhost-user/libvhost-user.c | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/contrib/libvhost-user/libvhost-user.c b/contrib/libvhost-user/libvhost-user.c
index b2de8ed0a8..7c8cd5878e 100644
--- a/contrib/libvhost-user/libvhost-user.c
+++ b/contrib/libvhost-user/libvhost-user.c
@@ -494,6 +494,40 @@ vu_set_mem_table_exec_postcopy(VuDev *dev, VhostUserMsg *vmsg)
         close(vmsg->fds[i]);
     }
 
+    /* TODO: Get address back to QEMU */
+    for (i = 0; i < dev->nregions; i++) {
+        VuDevRegion *dev_region = &dev->regions[i];
+#ifdef UFFDIO_REGISTER
+        /* We should already have an open ufd. Mark each memory
+         * range as ufd.
+         * Note: Do we need any madvises? Well it's not been accessed
+         * yet, still probably need no THP to be safe, discard to be safe?
+         */
+        struct uffdio_register reg_struct;
+        reg_struct.range.start = (uintptr_t)dev_region->mmap_addr;
+        reg_struct.range.len = dev_region->size + dev_region->mmap_offset;
+        reg_struct.mode = UFFDIO_REGISTER_MODE_MISSING;
+
+        if (ioctl(dev->postcopy_ufd, UFFDIO_REGISTER, &reg_struct)) {
+            vu_panic(dev, "%s: Failed to userfault region %d "
+                          "@%p + size:%zx offset: %zx: (ufd=%d)%s\n",
+                     __func__, i,
+                     dev_region->mmap_addr,
+                     dev_region->size, dev_region->mmap_offset,
+                     dev->postcopy_ufd, strerror(errno));
+            return false;
+        }
+        if (!(reg_struct.ioctls & ((__u64)1 << _UFFDIO_COPY))) {
+            vu_panic(dev, "%s Region (%d) doesn't support COPY",
+                     __func__, i);
+            return false;
+        }
+        DPRINT("%s: region %d: Registered userfault for %llx + %llx\n",
+                __func__, i, reg_struct.range.start, reg_struct.range.len);
+        /* TODO: Stash 'zero' support flags somewhere */
+#endif
+    }
+
     return false;
 }
 
-- 
2.14.3