[RFC PATCH v2 3/5] vhost-user-dev: Add cache BAR

[Albert Esteve <aesteve@redhat.com>]

Add a cache BAR in the vhost-user-device
into which files can be directly mapped.

The number, shmid, and size of the VIRTIO Shared
Memory subregions is retrieved through a get_shmem_config
message sent by the vhost-user-base module
on the realize step, after virtio_init().

By default, if VHOST_USER_PROTOCOL_F_SHMEM
feature is not supported by the backend,
there is no cache.

Signed-off-by: Albert Esteve <aesteve@redhat.com>
---
 hw/virtio/vhost-user-base.c       | 39 +++++++++++++++++++++++++++++--
 hw/virtio/vhost-user-device-pci.c | 37 ++++++++++++++++++++++++++---
 2 files changed, 71 insertions(+), 5 deletions(-)

diff --git a/hw/virtio/vhost-user-base.c b/hw/virtio/vhost-user-base.c
index a83167191e..e47c568a55 100644
--- a/hw/virtio/vhost-user-base.c
+++ b/hw/virtio/vhost-user-base.c
@@ -268,7 +268,9 @@ static void vub_device_realize(DeviceState *dev, Error **errp)
 {
     VirtIODevice *vdev = VIRTIO_DEVICE(dev);
     VHostUserBase *vub = VHOST_USER_BASE(dev);
-    int ret;
+    uint64_t memory_sizes[8];
+    void *cache_ptr;
+    int i, ret, nregions;
 
     if (!vub->chardev.chr) {
         error_setg(errp, "vhost-user-base: missing chardev");
@@ -311,7 +313,7 @@ static void vub_device_realize(DeviceState *dev, Error **errp)
 
     /* Allocate queues */
     vub->vqs = g_ptr_array_sized_new(vub->num_vqs);
-    for (int i = 0; i < vub->num_vqs; i++) {
+    for (i = 0; i < vub->num_vqs; i++) {
         g_ptr_array_add(vub->vqs,
                         virtio_add_queue(vdev, vub->vq_size,
                                          vub_handle_output));
@@ -328,6 +330,39 @@ static void vub_device_realize(DeviceState *dev, Error **errp)
         do_vhost_user_cleanup(vdev, vub);
     }
 
+    ret = vub->vhost_dev.vhost_ops->vhost_get_shmem_config(&vub->vhost_dev,
+                                                           &nregions,
+                                                           memory_sizes,
+                                                           errp);
+
+    if (ret < 0) {
+        do_vhost_user_cleanup(vdev, vub);
+    }
+
+    for (i = 0; i < nregions; i++) {
+        if (memory_sizes[i]) {
+            if (!is_power_of_2(memory_sizes[i]) ||
+                memory_sizes[i] < qemu_real_host_page_size()) {
+                error_setg(errp, "Shared memory %d size must be a power of 2 "
+                                 "no smaller than the page size", i);
+                return;
+            }
+
+            cache_ptr = mmap(NULL, memory_sizes[i], PROT_READ,
+                            MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+            if (cache_ptr == MAP_FAILED) {
+                error_setg(errp, "Unable to mmap blank cache: %s",
+                           strerror(errno));
+                return;
+            }
+
+            virtio_new_shmem_region(vdev);
+            memory_region_init_ram_ptr(&vdev->shmem_list[i],
+                                    OBJECT(vdev), "vub-shm-" + i,
+                                    memory_sizes[i], cache_ptr);
+        }
+    }
+
     qemu_chr_fe_set_handlers(&vub->chardev, NULL, NULL, vub_event, NULL,
                              dev, NULL, true);
 }
diff --git a/hw/virtio/vhost-user-device-pci.c b/hw/virtio/vhost-user-device-pci.c
index efaf55d3dd..314bacfb7a 100644
--- a/hw/virtio/vhost-user-device-pci.c
+++ b/hw/virtio/vhost-user-device-pci.c
@@ -8,14 +8,18 @@
  */
 
 #include "qemu/osdep.h"
+#include "qapi/error.h"
 #include "hw/qdev-properties.h"
 #include "hw/virtio/vhost-user-base.h"
 #include "hw/virtio/virtio-pci.h"
 
+#define VIRTIO_DEVICE_PCI_CACHE_BAR 2
+
 struct VHostUserDevicePCI {
     VirtIOPCIProxy parent_obj;
 
     VHostUserBase vub;
+    MemoryRegion cachebar;
 };
 
 #define TYPE_VHOST_USER_DEVICE_PCI "vhost-user-device-pci-base"
@@ -25,10 +29,37 @@ OBJECT_DECLARE_SIMPLE_TYPE(VHostUserDevicePCI, VHOST_USER_DEVICE_PCI)
 static void vhost_user_device_pci_realize(VirtIOPCIProxy *vpci_dev, Error **errp)
 {
     VHostUserDevicePCI *dev = VHOST_USER_DEVICE_PCI(vpci_dev);
-    DeviceState *vdev = DEVICE(&dev->vub);
-
+    DeviceState *dev_state = DEVICE(&dev->vub);
+    VirtIODevice *vdev = VIRTIO_DEVICE(dev_state);
+    uint64_t offset = 0, cache_size = 0;
+    int i;
+    
     vpci_dev->nvectors = 1;
-    qdev_realize(vdev, BUS(&vpci_dev->bus), errp);
+    qdev_realize(dev_state, BUS(&vpci_dev->bus), errp);
+
+    for (i = 0; i < vdev->n_shmem_regions; i++) {
+        if (vdev->shmem_list[i].size > UINT64_MAX - cache_size) {
+            error_setg(errp, "Total shared memory required overflow");
+            return;
+        }
+        cache_size = cache_size + vdev->shmem_list[i].size;
+    }
+    if (cache_size) {
+        memory_region_init(&dev->cachebar, OBJECT(vpci_dev),
+                           "vhost-device-pci-cachebar", cache_size);
+        for (i = 0; i < vdev->n_shmem_regions; i++) {
+            memory_region_add_subregion(&dev->cachebar, offset,
+                                        &vdev->shmem_list[i]);
+            virtio_pci_add_shm_cap(vpci_dev, VIRTIO_DEVICE_PCI_CACHE_BAR,
+                                   offset, vdev->shmem_list[i].size, i);
+            offset = offset + vdev->shmem_list[i].size;
+        }
+        pci_register_bar(&vpci_dev->pci_dev, VIRTIO_DEVICE_PCI_CACHE_BAR,
+                        PCI_BASE_ADDRESS_SPACE_MEMORY |
+                        PCI_BASE_ADDRESS_MEM_PREFETCH |
+                        PCI_BASE_ADDRESS_MEM_TYPE_64,
+                        &dev->cachebar);
+    }
 }
 
 static void vhost_user_device_pci_class_init(ObjectClass *klass, void *data)
-- 
2.45.2