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virtio: use MemoryRegionCache to access descriptors
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For now, the cache is created on every virtqueue_pop.  Later on,
direct descriptors will be able to reuse it.

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
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@bonzini @mstsirkin
bonzini authored and mstsirkin committed Feb 17, 2017
1 parent 91047df commit 5eba040
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Showing 2 changed files with 41 additions and 41 deletions.
80 changes: 39 additions & 41 deletions hw/virtio/virtio.c
View file
Expand Up @@ -120,9 +120,10 @@ void virtio_queue_update_rings(VirtIODevice *vdev, int n)
}

static void vring_desc_read(VirtIODevice *vdev, VRingDesc *desc,
uint8_t *desc_ptr, int i)
MemoryRegionCache *cache, int i)
{
memcpy(desc, desc_ptr + i * sizeof(VRingDesc), sizeof(VRingDesc));
address_space_read_cached(cache, i * sizeof(VRingDesc),
desc, sizeof(VRingDesc));
virtio_tswap64s(vdev, &desc->addr);
virtio_tswap32s(vdev, &desc->len);
virtio_tswap16s(vdev, &desc->flags);
Expand Down Expand Up @@ -407,7 +408,7 @@ enum {
};

static int virtqueue_read_next_desc(VirtIODevice *vdev, VRingDesc *desc,
void *desc_ptr, unsigned int max,
MemoryRegionCache *desc_cache, unsigned int max,
unsigned int *next)
{
/* If this descriptor says it doesn't chain, we're done. */
Expand All @@ -425,7 +426,7 @@ static int virtqueue_read_next_desc(VirtIODevice *vdev, VRingDesc *desc,
return VIRTQUEUE_READ_DESC_ERROR;
}

vring_desc_read(vdev, desc, desc_ptr, *next);
vring_desc_read(vdev, desc, desc_cache, *next);
return VIRTQUEUE_READ_DESC_MORE;
}

Expand All @@ -436,24 +437,25 @@ void virtqueue_get_avail_bytes(VirtQueue *vq, unsigned int *in_bytes,
VirtIODevice *vdev = vq->vdev;
unsigned int max, idx;
unsigned int total_bufs, in_total, out_total;
void *vring_desc_ptr;
void *indirect_desc_ptr = NULL;
hwaddr len = 0;
MemoryRegionCache vring_desc_cache;
MemoryRegionCache indirect_desc_cache = MEMORY_REGION_CACHE_INVALID;
int64_t len = 0;
int rc;

idx = vq->last_avail_idx;
total_bufs = in_total = out_total = 0;

max = vq->vring.num;
len = max * sizeof(VRingDesc);
vring_desc_ptr = address_space_map(vdev->dma_as, vq->vring.desc, &len, false);
len = address_space_cache_init(&vring_desc_cache, vdev->dma_as,
vq->vring.desc, max * sizeof(VRingDesc),
false);
if (len < max * sizeof(VRingDesc)) {
virtio_error(vdev, "Cannot map descriptor ring");
goto err;
}

while ((rc = virtqueue_num_heads(vq, idx)) > 0) {
void *desc_ptr = vring_desc_ptr;
MemoryRegionCache *desc_cache = &vring_desc_cache;
unsigned int num_bufs;
VRingDesc desc;
unsigned int i;
Expand All @@ -464,10 +466,9 @@ void virtqueue_get_avail_bytes(VirtQueue *vq, unsigned int *in_bytes,
goto err;
}

vring_desc_read(vdev, &desc, desc_ptr, i);
vring_desc_read(vdev, &desc, desc_cache, i);

if (desc.flags & VRING_DESC_F_INDIRECT) {
len = desc.len;
if (desc.len % sizeof(VRingDesc)) {
virtio_error(vdev, "Invalid size for indirect buffer table");
goto err;
Expand All @@ -480,17 +481,18 @@ void virtqueue_get_avail_bytes(VirtQueue *vq, unsigned int *in_bytes,
}

/* loop over the indirect descriptor table */
indirect_desc_ptr = address_space_map(vdev->dma_as, desc.addr,
&len, false);
desc_ptr = indirect_desc_ptr;
len = address_space_cache_init(&indirect_desc_cache,
vdev->dma_as,
desc.addr, desc.len, false);
desc_cache = &indirect_desc_cache;
if (len < desc.len) {
virtio_error(vdev, "Cannot map indirect buffer");
goto err;
}

max = desc.len / sizeof(VRingDesc);
num_bufs = i = 0;
vring_desc_read(vdev, &desc, desc_ptr, i);
vring_desc_read(vdev, &desc, desc_cache, i);
}

do {
Expand All @@ -509,16 +511,15 @@ void virtqueue_get_avail_bytes(VirtQueue *vq, unsigned int *in_bytes,
goto done;
}

rc = virtqueue_read_next_desc(vdev, &desc, desc_ptr, max, &i);
rc = virtqueue_read_next_desc(vdev, &desc, desc_cache, max, &i);
} while (rc == VIRTQUEUE_READ_DESC_MORE);

if (rc == VIRTQUEUE_READ_DESC_ERROR) {
goto err;
}

if (desc_ptr == indirect_desc_ptr) {
address_space_unmap(vdev->dma_as, desc_ptr, len, false, 0);
indirect_desc_ptr = NULL;
if (desc_cache == &indirect_desc_cache) {
address_space_cache_destroy(&indirect_desc_cache);
total_bufs++;
} else {
total_bufs = num_bufs;
Expand All @@ -530,10 +531,8 @@ void virtqueue_get_avail_bytes(VirtQueue *vq, unsigned int *in_bytes,
}

done:
if (indirect_desc_ptr) {
address_space_unmap(vdev->dma_as, indirect_desc_ptr, len, false, 0);
}
address_space_unmap(vdev->dma_as, vring_desc_ptr, len, false, 0);
address_space_cache_destroy(&indirect_desc_cache);
address_space_cache_destroy(&vring_desc_cache);
if (in_bytes) {
*in_bytes = in_total;
}
Expand Down Expand Up @@ -673,10 +672,10 @@ static void *virtqueue_alloc_element(size_t sz, unsigned out_num, unsigned in_nu
void *virtqueue_pop(VirtQueue *vq, size_t sz)
{
unsigned int i, head, max;
void *vring_desc_ptr;
void *indirect_desc_ptr = NULL;
void *desc_ptr;
hwaddr len;
MemoryRegionCache vring_desc_cache;
MemoryRegionCache indirect_desc_cache = MEMORY_REGION_CACHE_INVALID;
MemoryRegionCache *desc_cache;
int64_t len;
VirtIODevice *vdev = vq->vdev;
VirtQueueElement *elem = NULL;
unsigned out_num, in_num;
Expand Down Expand Up @@ -715,33 +714,34 @@ void *virtqueue_pop(VirtQueue *vq, size_t sz)

i = head;

len = max * sizeof(VRingDesc);
vring_desc_ptr = address_space_map(vdev->dma_as, vq->vring.desc, &len, false);
len = address_space_cache_init(&vring_desc_cache, vdev->dma_as,
vq->vring.desc, max * sizeof(VRingDesc),
false);
if (len < max * sizeof(VRingDesc)) {
virtio_error(vdev, "Cannot map descriptor ring");
goto done;
}

desc_ptr = vring_desc_ptr;
vring_desc_read(vdev, &desc, desc_ptr, i);
desc_cache = &vring_desc_cache;
vring_desc_read(vdev, &desc, desc_cache, i);
if (desc.flags & VRING_DESC_F_INDIRECT) {
if (desc.len % sizeof(VRingDesc)) {
virtio_error(vdev, "Invalid size for indirect buffer table");
goto done;
}

/* loop over the indirect descriptor table */
len = desc.len;
indirect_desc_ptr = address_space_map(vdev->dma_as, desc.addr, &len, false);
desc_ptr = indirect_desc_ptr;
len = address_space_cache_init(&indirect_desc_cache, vdev->dma_as,
desc.addr, desc.len, false);
desc_cache = &indirect_desc_cache;
if (len < desc.len) {
virtio_error(vdev, "Cannot map indirect buffer");
goto done;
}

max = desc.len / sizeof(VRingDesc);
i = 0;
vring_desc_read(vdev, &desc, desc_ptr, i);
vring_desc_read(vdev, &desc, desc_cache, i);
}

/* Collect all the descriptors */
Expand Down Expand Up @@ -772,7 +772,7 @@ void *virtqueue_pop(VirtQueue *vq, size_t sz)
goto err_undo_map;
}

rc = virtqueue_read_next_desc(vdev, &desc, desc_ptr, max, &i);
rc = virtqueue_read_next_desc(vdev, &desc, desc_cache, max, &i);
} while (rc == VIRTQUEUE_READ_DESC_MORE);

if (rc == VIRTQUEUE_READ_DESC_ERROR) {
Expand All @@ -795,10 +795,8 @@ void *virtqueue_pop(VirtQueue *vq, size_t sz)

trace_virtqueue_pop(vq, elem, elem->in_num, elem->out_num);
done:
if (indirect_desc_ptr) {
address_space_unmap(vdev->dma_as, indirect_desc_ptr, len, false, 0);
}
address_space_unmap(vdev->dma_as, vring_desc_ptr, len, false, 0);
address_space_cache_destroy(&indirect_desc_cache);
address_space_cache_destroy(&vring_desc_cache);

return elem;

Expand Down
2 changes: 2 additions & 0 deletions include/exec/memory.h
View file
Expand Up @@ -1426,6 +1426,8 @@ struct MemoryRegionCache {
bool is_write;
};

#define MEMORY_REGION_CACHE_INVALID ((MemoryRegionCache) { .mr = NULL })

/* address_space_cache_init: prepare for repeated access to a physical
* memory region
*
Expand Down

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