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

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 <dgilb...@redhat.com>
Reviewed-by: Peter Xu <pet...@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lur...@redhat.com>
---
 hw/virtio/trace-events |  3 +++
 hw/virtio/vhost-user.c | 31 ++++++++++++++++++++++++++++++-
 2 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/hw/virtio/trace-events b/hw/virtio/trace-events
index d7e9e1084b..3afd12cfea 100644
--- a/hw/virtio/trace-events
+++ b/hw/virtio/trace-events
@@ -7,6 +7,9 @@ vhost_region_add_section_abut(const char *name, uint64_t 
new_size) "%s: 0x%"PRIx
 vhost_section(const char *name, int r) "%s:%d"
 
 # hw/virtio/vhost-user.c
+vhost_user_postcopy_fault_handler(const char *name, uint64_t fault_address, 
int nregions) "%s: @0x%"PRIx64" nregions:%d"
+vhost_user_postcopy_fault_handler_loop(int i, uint64_t client_base, uint64_t 
size) "%d: client 0x%"PRIx64" +0x%"PRIx64
+vhost_user_postcopy_fault_handler_found(int i, uint64_t region_offset, 
uint64_t rb_offset) "%d: region_offset: 0x%"PRIx64" rb_offset:0x%"PRIx64
 vhost_user_postcopy_listen(void) ""
 vhost_user_set_mem_table_postcopy(uint64_t client_addr, uint64_t qhva, int 
reply_i, int region_i) "client:0x%"PRIx64" for hva: 0x%"PRIx64" reply %d region 
%d"
 vhost_user_set_mem_table_withfd(int index, const char *name, uint64_t 
memory_size, uint64_t guest_phys_addr, uint64_t userspace_addr, uint64_t 
offset) "%d:%s: size:0x%"PRIx64" GPA:0x%"PRIx64" QVA/userspace:0x%"PRIx64" RB 
offset:0x%"PRIx64
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;
 }
 
 /*
-- 
2.14.3


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