vfio/container: restore DMA vaddr

In new QEMU, do not register the memory listener at device creation time.
Register it later, in the container post_load handler, after all vmstate
that may affect regions and mapping boundaries has been loaded.  The
post_load registration will cause the listener to invoke its callback on
each flat section, and the calls will match the mappings remembered by the
kernel.

The listener calls a special dma_map handler that passes the new VA of each
section to the kernel using VFIO_DMA_MAP_FLAG_VADDR.  Restore the normal
handler at the end.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Link: https://lore.kernel.org/qemu-devel/1749569991-25171-7-git-send-email-steven.sistare@oracle.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>

hw/vfio/container.c

@@ -136,6 +136,8 @@ static int vfio_legacy_dma_unmap_one(const VFIOContainerBase *bcontainer,
     int ret;
     Error *local_err = NULL;
 
+    g_assert(!cpr_is_incoming());
+
     if (iotlb && vfio_container_dirty_tracking_is_started(bcontainer)) {
         if (!vfio_container_devices_dirty_tracking_is_supported(bcontainer) &&
             bcontainer->dirty_pages_supported) {
@@ -690,8 +692,17 @@ static bool vfio_container_connect(VFIOGroup *group, AddressSpace *as,
     }
     group_was_added = true;
 
-    if (!vfio_listener_register(bcontainer, errp)) {
-        goto fail;
+    /*
+     * If CPR, register the listener later, after all state that may
+     * affect regions and mapping boundaries has been cpr load'ed.  Later,
+     * the listener will invoke its callback on each flat section and call
+     * dma_map to supply the new vaddr, and the calls will match the mappings
+     * remembered by the kernel.
+     */
+    if (!cpr_is_incoming()) {
+        if (!vfio_listener_register(bcontainer, errp)) {
+            goto fail;
+        }
     }
 
     bcontainer->initialized = true;

hw/vfio/cpr-legacy.c

@@ -9,11 +9,13 @@
 #include "qemu/osdep.h"
 #include "hw/vfio/vfio-container.h"
 #include "hw/vfio/vfio-device.h"
+#include "hw/vfio/vfio-listener.h"
 #include "migration/blocker.h"
 #include "migration/cpr.h"
 #include "migration/migration.h"
 #include "migration/vmstate.h"
 #include "qapi/error.h"
+#include "qemu/error-report.h"
 
 static bool vfio_dma_unmap_vaddr_all(VFIOContainer *container, Error **errp)
 {
@@ -30,6 +32,32 @@ static bool vfio_dma_unmap_vaddr_all(VFIOContainer *container, Error **errp)
     return true;
 }
 
+/*
+ * Set the new @vaddr for any mappings registered during cpr load.
+ * The incoming state is cleared thereafter.
+ */
+static int vfio_legacy_cpr_dma_map(const VFIOContainerBase *bcontainer,
+                                   hwaddr iova, ram_addr_t size, void *vaddr,
+                                   bool readonly, MemoryRegion *mr)
+{
+    const VFIOContainer *container = container_of(bcontainer, VFIOContainer,
+                                                  bcontainer);
+    struct vfio_iommu_type1_dma_map map = {
+        .argsz = sizeof(map),
+        .flags = VFIO_DMA_MAP_FLAG_VADDR,
+        .vaddr = (__u64)(uintptr_t)vaddr,
+        .iova = iova,
+        .size = size,
+    };
+
+    g_assert(cpr_is_incoming());
+
+    if (ioctl(container->fd, VFIO_IOMMU_MAP_DMA, &map)) {
+        return -errno;
+    }
+
+    return 0;
+}
 
 static bool vfio_cpr_supported(VFIOContainer *container, Error **errp)
 {
@@ -58,11 +86,34 @@ static int vfio_container_pre_save(void *opaque)
     return 0;
 }
 
+static int vfio_container_post_load(void *opaque, int version_id)
+{
+    VFIOContainer *container = opaque;
+    VFIOContainerBase *bcontainer = &container->bcontainer;
+    VFIOGroup *group;
+    Error *local_err = NULL;
+
+    if (!vfio_listener_register(bcontainer, &local_err)) {
+        error_report_err(local_err);
+        return -1;
+    }
+
+    QLIST_FOREACH(group, &container->group_list, container_next) {
+        VFIOIOMMUClass *vioc = VFIO_IOMMU_GET_CLASS(bcontainer);
+
+        /* Restore original dma_map function */
+        vioc->dma_map = container->cpr.saved_dma_map;
+    }
+    return 0;
+}
+
 static const VMStateDescription vfio_container_vmstate = {
     .name = "vfio-container",
     .version_id = 0,
     .minimum_version_id = 0,
+    .priority = MIG_PRI_LOW,  /* Must happen after devices and groups */
     .pre_save = vfio_container_pre_save,
+    .post_load = vfio_container_post_load,
     .needed = cpr_incoming_needed,
     .fields = (VMStateField[]) {
         VMSTATE_END_OF_LIST()
@@ -85,6 +136,12 @@ bool vfio_legacy_cpr_register_container(VFIOContainer *container, Error **errp)
 
     vmstate_register(NULL, -1, &vfio_container_vmstate, container);
 
+    /* During incoming CPR, divert calls to dma_map. */
+    if (cpr_is_incoming()) {
+        VFIOIOMMUClass *vioc = VFIO_IOMMU_GET_CLASS(bcontainer);
+        container->cpr.saved_dma_map = vioc->dma_map;
+        vioc->dma_map = vfio_legacy_cpr_dma_map;
+    }
     return true;
 }
 

include/hw/vfio/vfio-cpr.h

@@ -17,6 +17,9 @@ struct VFIOGroup;
 
 typedef struct VFIOContainerCPR {
     Error *blocker;
+    int (*saved_dma_map)(const struct VFIOContainerBase *bcontainer,
+                         hwaddr iova, ram_addr_t size,
+                         void *vaddr, bool readonly, MemoryRegion *mr);
 } VFIOContainerCPR;