virtio-gpu: Add udmabuf helpers

Add helper functions to create a dmabuf for a resource and mmap it.
Also, introduce the fields blob and blob_size so that these helpers
can start to use them but the full picture will emerge only after
adding create_blob API in patch 8 of this series.

To be able to create a dmabuf using the udmabuf driver, Qemu needs
to be lauched with the memfd memory backend like this:

qemu-system-x86_64 -m 8192m -object memory-backend-memfd,id=mem1,size=8192M
-machine memory-backend=mem1

Based-on-patch-by: Gerd Hoffmann <kraxel@redhat.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Vivek Kasireddy <vivek.kasireddy@intel.com>
Message-Id: <20210526231429.1045476-4-vivek.kasireddy@intel.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

hw/display/meson.build

@@ -56,6 +56,7 @@ if config_all_devices.has_key('CONFIG_VIRTIO_GPU')
   virtio_gpu_ss = ss.source_set()
   virtio_gpu_ss.add(when: 'CONFIG_VIRTIO_GPU',
                     if_true: [files('virtio-gpu-base.c', 'virtio-gpu.c'), pixman])
+  virtio_gpu_ss.add(when: 'CONFIG_LINUX', if_true: files('virtio-gpu-udmabuf.c'))
   virtio_gpu_ss.add(when: 'CONFIG_VHOST_USER_GPU', if_true: files('vhost-user-gpu.c'))
   hw_display_modules += {'virtio-gpu': virtio_gpu_ss}
 

hw/display/virtio-gpu-udmabuf.c

@@ -0,0 +1,158 @@
+/*
+ * Virtio GPU Device
+ *
+ * Copyright Red Hat, Inc. 2013-2014
+ *
+ * Authors:
+ *     Dave Airlie <airlied@redhat.com>
+ *     Gerd Hoffmann <kraxel@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#include "qemu/osdep.h"
+#include "qemu/units.h"
+#include "qemu-common.h"
+#include "qemu/iov.h"
+#include "ui/console.h"
+#include "hw/virtio/virtio-gpu.h"
+#include "hw/virtio/virtio-gpu-pixman.h"
+#include "trace.h"
+#include "exec/ramblock.h"
+#include "sysemu/hostmem.h"
+#include <sys/ioctl.h>
+#include <fcntl.h>
+#include <linux/memfd.h>
+#include "qemu/memfd.h"
+#include "standard-headers/linux/udmabuf.h"
+
+static void virtio_gpu_create_udmabuf(struct virtio_gpu_simple_resource *res)
+{
+    struct udmabuf_create_list *list;
+    RAMBlock *rb;
+    ram_addr_t offset;
+    int udmabuf, i;
+
+    udmabuf = udmabuf_fd();
+    if (udmabuf < 0) {
+        return;
+    }
+
+    list = g_malloc0(sizeof(struct udmabuf_create_list) +
+                     sizeof(struct udmabuf_create_item) * res->iov_cnt);
+
+    for (i = 0; i < res->iov_cnt; i++) {
+        rcu_read_lock();
+        rb = qemu_ram_block_from_host(res->iov[i].iov_base, false, &offset);
+        rcu_read_unlock();
+
+        if (!rb || rb->fd < 0) {
+            g_free(list);
+            return;
+        }
+
+        list->list[i].memfd  = rb->fd;
+        list->list[i].offset = offset;
+        list->list[i].size   = res->iov[i].iov_len;
+    }
+
+    list->count = res->iov_cnt;
+    list->flags = UDMABUF_FLAGS_CLOEXEC;
+
+    res->dmabuf_fd = ioctl(udmabuf, UDMABUF_CREATE_LIST, list);
+    if (res->dmabuf_fd < 0) {
+        warn_report("%s: UDMABUF_CREATE_LIST: %s", __func__,
+                    strerror(errno));
+    }
+    g_free(list);
+}
+
+static void virtio_gpu_remap_udmabuf(struct virtio_gpu_simple_resource *res)
+{
+    res->remapped = mmap(NULL, res->blob_size, PROT_READ,
+                         MAP_SHARED, res->dmabuf_fd, 0);
+    if (res->remapped == MAP_FAILED) {
+        warn_report("%s: dmabuf mmap failed: %s", __func__,
+                    strerror(errno));
+        res->remapped = NULL;
+    }
+}
+
+static void virtio_gpu_destroy_udmabuf(struct virtio_gpu_simple_resource *res)
+{
+    if (res->remapped) {
+        munmap(res->remapped, res->blob_size);
+        res->remapped = NULL;
+    }
+    if (res->dmabuf_fd >= 0) {
+        close(res->dmabuf_fd);
+        res->dmabuf_fd = -1;
+    }
+}
+
+static int find_memory_backend_type(Object *obj, void *opaque)
+{
+    bool *memfd_backend = opaque;
+    int ret;
+
+    if (object_dynamic_cast(obj, TYPE_MEMORY_BACKEND)) {
+        HostMemoryBackend *backend = MEMORY_BACKEND(obj);
+        RAMBlock *rb = backend->mr.ram_block;
+
+        if (rb && rb->fd > 0) {
+            ret = fcntl(rb->fd, F_GET_SEALS);
+            if (ret > 0) {
+                *memfd_backend = true;
+            }
+        }
+    }
+
+    return 0;
+}
+
+bool virtio_gpu_have_udmabuf(void)
+{
+    Object *memdev_root;
+    int udmabuf;
+    bool memfd_backend = false;
+
+    udmabuf = udmabuf_fd();
+    if (udmabuf < 0) {
+        return false;
+    }
+
+    memdev_root = object_resolve_path("/objects", NULL);
+    object_child_foreach(memdev_root, find_memory_backend_type, &memfd_backend);
+
+    return memfd_backend;
+}
+
+void virtio_gpu_init_udmabuf(struct virtio_gpu_simple_resource *res)
+{
+    void *pdata = NULL;
+
+    res->dmabuf_fd = -1;
+    if (res->iov_cnt == 1) {
+        pdata = res->iov[0].iov_base;
+    } else {
+        virtio_gpu_create_udmabuf(res);
+        if (res->dmabuf_fd < 0) {
+            return;
+        }
+        virtio_gpu_remap_udmabuf(res);
+        if (!res->remapped) {
+            return;
+        }
+        pdata = res->remapped;
+    }
+
+    res->blob = pdata;
+}
+
+void virtio_gpu_fini_udmabuf(struct virtio_gpu_simple_resource *res)
+{
+    if (res->remapped) {
+        virtio_gpu_destroy_udmabuf(res);
+    }
+}

include/hw/virtio/virtio-gpu.h

@@ -50,6 +50,12 @@ struct virtio_gpu_simple_resource {
     uint32_t scanout_bitmask;
     pixman_image_t *image;
     uint64_t hostmem;
+
+    uint64_t blob_size;
+    void *blob;
+    int dmabuf_fd;
+    uint8_t *remapped;
+
     QTAILQ_ENTRY(virtio_gpu_simple_resource) next;
 };
 
@@ -238,6 +244,11 @@ void virtio_gpu_update_cursor_data(VirtIOGPU *g,
                                    struct virtio_gpu_scanout *s,
                                    uint32_t resource_id);
 
+/* virtio-gpu-udmabuf.c */
+bool virtio_gpu_have_udmabuf(void);
+void virtio_gpu_init_udmabuf(struct virtio_gpu_simple_resource *res);
+void virtio_gpu_fini_udmabuf(struct virtio_gpu_simple_resource *res);
+
 /* virtio-gpu-3d.c */
 void virtio_gpu_virgl_process_cmd(VirtIOGPU *g,
                                   struct virtio_gpu_ctrl_command *cmd);