[Qemu-devel] [PATCH qemu v10 13/14] vfio: spapr: Add SPAPR IOMMU v2 support (DMA memory preregistering)

[Alexey Kardashevskiy]

This makes use of the new "memory registering" feature. The idea is
to provide the userspace ability to notify the host kernel about pages
which are going to be used for DMA. Having this information, the host
kernel can pin them all once per user process, do locked pages
accounting (once) and not spent time on doing that in real time with
possible failures which cannot be handled nicely in some cases.

This adds a guest RAM memory listener which notifies a VFIO container
about memory which needs to be pinned/unpinned. VFIO MMIO regions
(i.e. "skip dump" regions) are skipped.

The feature is only enabled for SPAPR IOMMU v2. The host kernel changes
are required. Since v2 does not need/support VFIO_IOMMU_ENABLE, this does
not call it when v2 is detected and enabled.

This does not change the guest visible interface.

Signed-off-by: Alexey Kardashevskiy <address@hidden>
Reviewed-by: David Gibson <address@hidden>
---
Changes:
v9:
* since there is no more SPAPR-specific data in container::iommu_data,
the memory preregistration fields are common and potentially can be used
by other architectures

v7:
* in vfio_spapr_ram_listener_region_del(), do unref() after ioctl()
* s'ramlistener'register_listener'

v6:
* fixed commit log (s/guest/userspace/), added note about no guest visible
change
* fixed error checking if ram registration failed
* added alignment check for section->offset_within_region

v5:
* simplified the patch
* added trace points
* added round_up() for the size
* SPAPR IOMMU v2 used
---
 hw/vfio/common.c              | 109 ++++++++++++++++++++++++++++++++++++++----
 include/hw/vfio/vfio-common.h |   3 ++
 trace-events                  |   1 +
 3 files changed, 104 insertions(+), 9 deletions(-)

diff --git a/hw/vfio/common.c b/hw/vfio/common.c
index 8eacfd7..0c7ba8c 100644
--- a/hw/vfio/common.c
+++ b/hw/vfio/common.c
@@ -488,6 +488,76 @@ static void vfio_listener_release(VFIOContainer *container)
     memory_listener_unregister(&container->iommu_data.type1.listener);
 }
 
+static void vfio_ram_do_region(VFIOContainer *container,
+                              MemoryRegionSection *section, unsigned long req)
+{
+    int ret;
+    struct vfio_iommu_spapr_register_memory reg = { .argsz = sizeof(reg) };
+
+    if (!memory_region_is_ram(section->mr) ||
+        memory_region_is_skip_dump(section->mr)) {
+        return;
+    }
+
+    if (unlikely((section->offset_within_region & (getpagesize() - 1)))) {
+        error_report("%s received unaligned region", __func__);
+        return;
+    }
+
+    reg.vaddr = (__u64) memory_region_get_ram_ptr(section->mr) +
+        section->offset_within_region;
+    reg.size = ROUND_UP(int128_get64(section->size), TARGET_PAGE_SIZE);
+
+    ret = ioctl(container->fd, req, &reg);
+    trace_vfio_ram_register(_IOC_NR(req) - VFIO_BASE, reg.vaddr, reg.size,
+            ret ? -errno : 0);
+    if (!ret) {
+        return;
+    }
+
+    /*
+     * On the initfn path, store the first error in the container so we
+     * can gracefully fail.  Runtime, there's not much we can do other
+     * than throw a hardware error.
+     */
+    if (!container->iommu_data.ram_reg_initialized) {
+        if (!container->iommu_data.ram_reg_error) {
+            container->iommu_data.ram_reg_error = -errno;
+        }
+    } else {
+        hw_error("vfio: RAM registering failed, unable to continue");
+    }
+}
+
+static void vfio_ram_listener_region_add(MemoryListener *listener,
+                                         MemoryRegionSection *section)
+{
+    VFIOContainer *container = container_of(listener, VFIOContainer,
+                                            iommu_data.register_listener);
+    memory_region_ref(section->mr);
+    vfio_ram_do_region(container, section, VFIO_IOMMU_SPAPR_REGISTER_MEMORY);
+}
+
+static void vfio_ram_listener_region_del(MemoryListener *listener,
+                                         MemoryRegionSection *section)
+{
+    VFIOContainer *container = container_of(listener, VFIOContainer,
+                                            iommu_data.register_listener);
+    vfio_ram_do_region(container, section, VFIO_IOMMU_SPAPR_UNREGISTER_MEMORY);
+    memory_region_unref(section->mr);
+}
+
+static const MemoryListener vfio_ram_memory_listener = {
+    .region_add = vfio_ram_listener_region_add,
+    .region_del = vfio_ram_listener_region_del,
+};
+
+static void vfio_spapr_listener_release_v2(VFIOContainer *container)
+{
+    memory_listener_unregister(&container->iommu_data.register_listener);
+    vfio_listener_release(container);
+}
+
 int vfio_mmap_region(Object *obj, VFIORegion *region,
                      MemoryRegion *mem, MemoryRegion *submem,
                      void **map, size_t size, off_t offset,
@@ -698,14 +768,18 @@ static int vfio_connect_container(VFIOGroup *group, 
AddressSpace *as)
 
         container->iommu_data.type1.initialized = true;
 
-    } else if (ioctl(fd, VFIO_CHECK_EXTENSION, VFIO_SPAPR_TCE_IOMMU)) {
+    } else if (ioctl(fd, VFIO_CHECK_EXTENSION, VFIO_SPAPR_TCE_IOMMU) ||
+               ioctl(fd, VFIO_CHECK_EXTENSION, VFIO_SPAPR_TCE_v2_IOMMU)) {
+        bool v2 = !!ioctl(fd, VFIO_CHECK_EXTENSION, VFIO_SPAPR_TCE_v2_IOMMU);
+
         ret = ioctl(group->fd, VFIO_GROUP_SET_CONTAINER, &fd);
         if (ret) {
             error_report("vfio: failed to set group container: %m");
             ret = -errno;
             goto free_container_exit;
         }
-        ret = ioctl(fd, VFIO_SET_IOMMU, VFIO_SPAPR_TCE_IOMMU);
+        ret = ioctl(fd, VFIO_SET_IOMMU,
+                v2 ? VFIO_SPAPR_TCE_v2_IOMMU : VFIO_SPAPR_TCE_IOMMU);
         if (ret) {
             error_report("vfio: failed to set iommu for container: %m");
             ret = -errno;
@@ -717,19 +791,36 @@ static int vfio_connect_container(VFIOGroup *group, 
AddressSpace *as)
          * when container fd is closed so we do not call it explicitly
          * in this file.
          */
-        ret = ioctl(fd, VFIO_IOMMU_ENABLE);
-        if (ret) {
-            error_report("vfio: failed to enable container: %m");
-            ret = -errno;
-            goto free_container_exit;
+        if (!v2) {
+            ret = ioctl(fd, VFIO_IOMMU_ENABLE);
+            if (ret) {
+                error_report("vfio: failed to enable container: %m");
+                ret = -errno;
+                goto free_container_exit;
+            }
         }
 
         container->iommu_data.type1.listener = vfio_memory_listener;
-        container->iommu_data.release = vfio_listener_release;
-
         memory_listener_register(&container->iommu_data.type1.listener,
                                  container->space->as);
 
+        if (!v2) {
+            container->iommu_data.release = vfio_listener_release;
+        } else {
+            container->iommu_data.release = vfio_spapr_listener_release_v2;
+            container->iommu_data.register_listener =
+                    vfio_ram_memory_listener;
+            memory_listener_register(&container->iommu_data.register_listener,
+                                     &address_space_memory);
+
+            if (container->iommu_data.ram_reg_error) {
+                error_report("vfio: RAM memory listener initialization failed 
for container");
+                goto listener_release_exit;
+            }
+
+            container->iommu_data.ram_reg_initialized = true;
+        }
+
     } else {
         error_report("vfio: No available IOMMU models");
         ret = -EINVAL;
diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
index 59a321d..b132248 100644
--- a/include/hw/vfio/vfio-common.h
+++ b/include/hw/vfio/vfio-common.h
@@ -79,6 +79,9 @@ typedef struct VFIOContainer {
             VFIOType1 type1;
         };
         void (*release)(struct VFIOContainer *);
+        MemoryListener register_listener;
+        int ram_reg_error;
+        bool ram_reg_initialized;
     } iommu_data;
     QLIST_HEAD(, VFIOGuestIOMMU) giommu_list;
     QLIST_HEAD(, VFIOGroup) group_list;
diff --git a/trace-events b/trace-events
index a994019..b300e94 100644
--- a/trace-events
+++ b/trace-events
@@ -1584,6 +1584,7 @@ vfio_disconnect_container(int fd) "close container->fd=%d"
 vfio_put_group(int fd) "close group->fd=%d"
 vfio_get_device(const char * name, unsigned int flags, unsigned int 
num_regions, unsigned int num_irqs) "Device %s flags: %u, regions: %u, irqs: %u"
 vfio_put_base_device(int fd) "close vdev->fd=%d"
+vfio_ram_register(int req, uint64_t va, uint64_t size, int ret) "req=%d 
va=%"PRIx64" size=%"PRIx64" ret=%d"
 
 # hw/vfio/platform.c
 vfio_platform_populate_regions(int region_index, unsigned long flag, unsigned 
long size, int fd, unsigned long offset) "- region %d flags = 0x%lx, size = 
0x%lx, fd= %d, offset = 0x%lx"
-- 
2.4.0.rc3.8.gfb3e7d5