[V2,12/45] vfio/container: restore DMA vaddr

Commit Message

Steven Sistare Feb. 14, 2025, 2:13 p.m. UTC

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 <[e-mail]>
---
 hw/vfio/container.c  | 15 +++++++++++++--
 hw/vfio/cpr-legacy.c | 43 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 56 insertions(+), 2 deletions(-)

Patch

diff --git a/hw/vfio/container.c b/hw/vfio/container.c
index 931c435..d26f78e 100644
--- a/hw/vfio/container.c
+++ b/hw/vfio/container.c
@@ -133,6 +133,8 @@  static int vfio_legacy_dma_unmap(const VFIOContainerBase *bcontainer,
     int ret;
     Error *local_err = NULL;
 
+    assert(!container->cpr.reused);
+
     if (iotlb && vfio_devices_all_dirty_tracking_started(bcontainer)) {
         if (!vfio_devices_all_device_dirty_tracking(bcontainer) &&
             bcontainer->dirty_pages_supported) {
@@ -688,8 +690,17 @@  static bool vfio_connect_container(VFIOGroup *group, AddressSpace *as,
     }
     group_was_added = true;
 
-    bcontainer->listener = vfio_memory_listener;
-    memory_listener_register(&bcontainer->listener, bcontainer->space->as);
+    /*
+     * If reused, 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_reused) {
+        bcontainer->listener = vfio_memory_listener;
+        memory_listener_register(&bcontainer->listener, bcontainer->space->as);
+    }
 
     if (bcontainer->error) {
         error_propagate_prepend(errp, bcontainer->error,
diff --git a/hw/vfio/cpr-legacy.c b/hw/vfio/cpr-legacy.c
index 97a64e7..bb5f802 100644
--- a/hw/vfio/cpr-legacy.c
+++ b/hw/vfio/cpr-legacy.c
@@ -14,6 +14,7 @@ 
 #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 +31,34 @@  static bool vfio_dma_unmap_vaddr_all(VFIOContainer *container, Error **errp)
     return true;
 }
 
+/*
+ * Set the new @vaddr for any mappings registered during cpr load.
+ * Reused is cleared thereafter.
+ */
+static int vfio_legacy_cpr_dma_map(const VFIOContainerBase *bcontainer,
+                                   hwaddr iova, ram_addr_t size, void *vaddr,
+                                   bool readonly)
+{
+    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,
+    };
+
+    assert(container->cpr.reused);
+
+    if (ioctl(container->fd, VFIO_IOMMU_MAP_DMA, &map)) {
+        error_report("vfio_legacy_cpr_dma_map (iova %lu, size %ld, va %p): %s",
+                     iova, size, vaddr, strerror(errno));
+        return -errno;
+    }
+
+    return 0;
+}
 
 static bool vfio_cpr_supported(VFIOContainer *container, Error **errp)
 {
@@ -61,12 +90,20 @@  static int vfio_container_pre_save(void *opaque)
 static int vfio_container_post_load(void *opaque, int version_id)
 {
     VFIOContainer *container = opaque;
+    VFIOContainerBase *bcontainer = &container->bcontainer;
     VFIOGroup *group;
     VFIODevice *vbasedev;
 
+    bcontainer->listener = vfio_memory_listener;
+    memory_listener_register(&bcontainer->listener, bcontainer->space->as);
     container->cpr.reused = false;
 
     QLIST_FOREACH(group, &container->group_list, container_next) {
+        VFIOIOMMUClass *vioc = VFIO_IOMMU_GET_CLASS(bcontainer);
+
+        /* Restore original dma_map function */
+        vioc->dma_map = vfio_legacy_dma_map;
+
         QLIST_FOREACH(vbasedev, &group->device_list, next) {
             vbasedev->cpr.reused = false;
         }
@@ -78,6 +115,7 @@  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_needed_for_reuse,
@@ -102,6 +140,11 @@  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 (container->cpr.reused) {
+        VFIOIOMMUClass *vioc = VFIO_IOMMU_GET_CLASS(bcontainer);
+        vioc->dma_map = vfio_legacy_cpr_dma_map;
+    }
     return true;
 }