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Message-ID: <CACGkMEvz55WO+TN2KCv+KLvdT-ZxLike81maahBeVanrCk_Lrg@mail.gmail.com>
Date: Wed, 31 Jan 2024 17:12:10 +0800
From: Jason Wang <jasowang@...hat.com>
To: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
Cc: virtualization@...ts.linux.dev, Richard Weinberger <richard@....at>,
Anton Ivanov <anton.ivanov@...bridgegreys.com>, Johannes Berg <johannes@...solutions.net>,
"Michael S. Tsirkin" <mst@...hat.com>, "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Hans de Goede <hdegoede@...hat.com>,
Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
Vadim Pasternak <vadimp@...dia.com>, Bjorn Andersson <andersson@...nel.org>,
Mathieu Poirier <mathieu.poirier@...aro.org>, Cornelia Huck <cohuck@...hat.com>,
Halil Pasic <pasic@...ux.ibm.com>, Eric Farman <farman@...ux.ibm.com>,
Heiko Carstens <hca@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>,
Alexander Gordeev <agordeev@...ux.ibm.com>, Christian Borntraeger <borntraeger@...ux.ibm.com>,
Sven Schnelle <svens@...ux.ibm.com>, Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>, Jesper Dangaard Brouer <hawk@...nel.org>,
John Fastabend <john.fastabend@...il.com>, Benjamin Berg <benjamin.berg@...el.com>,
Yang Li <yang.lee@...ux.alibaba.com>, linux-um@...ts.infradead.org,
netdev@...r.kernel.org, platform-driver-x86@...r.kernel.org,
linux-remoteproc@...r.kernel.org, linux-s390@...r.kernel.org,
kvm@...r.kernel.org, bpf@...r.kernel.org
Subject: Re: [PATCH vhost 03/17] virtio_ring: packed: structure the indirect
desc table
On Tue, Jan 30, 2024 at 7:42 PM Xuan Zhuo <xuanzhuo@...ux.alibaba.com> wrote:
>
> This commit structure the indirect desc table.
> Then we can get the desc num directly when doing unmap.
>
> And save the dma info to the struct, then the indirect
> will not use the dma fields of the desc_extra. The subsequent
> commits will make the dma fields are optional. But for
> the indirect case, we must record the dma info.
>
> Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
> ---
> drivers/virtio/virtio_ring.c | 63 ++++++++++++++++++++----------------
> 1 file changed, 35 insertions(+), 28 deletions(-)
>
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index 7280a1706cca..dd03bc5a81fe 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -72,9 +72,16 @@ struct vring_desc_state_split {
> struct vring_desc *indir_desc; /* Indirect descriptor, if any. */
> };
>
> +struct vring_packed_desc_indir {
> + dma_addr_t addr; /* Descriptor Array DMA addr. */
> + u32 len; /* Descriptor Array length. */
> + u32 num;
> + struct vring_packed_desc desc[];
> +};
> +
> struct vring_desc_state_packed {
> void *data; /* Data for callback. */
> - struct vring_packed_desc *indir_desc; /* Indirect descriptor, if any. */
> + struct vring_packed_desc_indir *indir_desc; /* Indirect descriptor, if any. */
> u16 num; /* Descriptor list length. */
> u16 last; /* The last desc state in a list. */
> };
> @@ -1249,10 +1256,13 @@ static void vring_unmap_desc_packed(const struct vring_virtqueue *vq,
> DMA_FROM_DEVICE : DMA_TO_DEVICE);
> }
>
> -static struct vring_packed_desc *alloc_indirect_packed(unsigned int total_sg,
> +static struct vring_packed_desc_indir *alloc_indirect_packed(unsigned int total_sg,
> gfp_t gfp)
> {
> - struct vring_packed_desc *desc;
> + struct vring_packed_desc_indir *in_desc;
> + u32 size;
> +
> + size = struct_size(in_desc, desc, total_sg);
>
> /*
> * We require lowmem mappings for the descriptors because
> @@ -1261,9 +1271,10 @@ static struct vring_packed_desc *alloc_indirect_packed(unsigned int total_sg,
> */
> gfp &= ~__GFP_HIGHMEM;
>
> - desc = kmalloc_array(total_sg, sizeof(struct vring_packed_desc), gfp);
>
> - return desc;
> + in_desc = kmalloc(size, gfp);
> +
> + return in_desc;
> }
>
> static int virtqueue_add_indirect_packed(struct vring_virtqueue *vq,
> @@ -1274,6 +1285,7 @@ static int virtqueue_add_indirect_packed(struct vring_virtqueue *vq,
> void *data,
> gfp_t gfp)
> {
> + struct vring_packed_desc_indir *in_desc;
> struct vring_packed_desc *desc;
> struct scatterlist *sg;
> unsigned int i, n, err_idx;
> @@ -1281,10 +1293,12 @@ static int virtqueue_add_indirect_packed(struct vring_virtqueue *vq,
> dma_addr_t addr;
>
> head = vq->packed.next_avail_idx;
> - desc = alloc_indirect_packed(total_sg, gfp);
> - if (!desc)
> + in_desc = alloc_indirect_packed(total_sg, gfp);
> + if (!in_desc)
> return -ENOMEM;
>
> + desc = in_desc->desc;
> +
> if (unlikely(vq->vq.num_free < 1)) {
> pr_debug("Can't add buf len 1 - avail = 0\n");
> kfree(desc);
> @@ -1321,17 +1335,15 @@ static int virtqueue_add_indirect_packed(struct vring_virtqueue *vq,
> goto unmap_release;
> }
>
> + in_desc->num = i;
> + in_desc->addr = addr;
> + in_desc->len = total_sg * sizeof(struct vring_packed_desc);
It looks to me if we don't use dma_api we don't even need these steps?
> +
> vq->packed.vring.desc[head].addr = cpu_to_le64(addr);
> vq->packed.vring.desc[head].len = cpu_to_le32(total_sg *
> sizeof(struct vring_packed_desc));
> vq->packed.vring.desc[head].id = cpu_to_le16(id);
>
> - if (vring_need_unmap_buffer(vq)) {
> - vq->packed.desc_extra[id].addr = addr;
> - vq->packed.desc_extra[id].len = total_sg *
> - sizeof(struct vring_packed_desc);
> - }
> -
> vq->packed.desc_extra[id].flags = VRING_DESC_F_INDIRECT |
> vq->packed.avail_used_flags;
>
> @@ -1362,7 +1374,7 @@ static int virtqueue_add_indirect_packed(struct vring_virtqueue *vq,
> /* Store token and indirect buffer state. */
> vq->packed.desc_state[id].num = 1;
> vq->packed.desc_state[id].data = data;
> - vq->packed.desc_state[id].indir_desc = desc;
> + vq->packed.desc_state[id].indir_desc = in_desc;
> vq->packed.desc_state[id].last = id;
>
> vq->num_added += 1;
> @@ -1381,7 +1393,7 @@ static int virtqueue_add_indirect_packed(struct vring_virtqueue *vq,
> vring_unmap_desc_packed(vq, &desc[i]);
>
> free_desc:
> - kfree(desc);
> + kfree(in_desc);
>
> END_USE(vq);
> return -ENOMEM;
> @@ -1595,7 +1607,6 @@ static void detach_buf_packed(struct vring_virtqueue *vq,
> unsigned int id, void **ctx)
> {
> struct vring_desc_state_packed *state = NULL;
> - struct vring_packed_desc *desc;
> unsigned int i, curr;
> u16 flags;
>
> @@ -1621,28 +1632,24 @@ static void detach_buf_packed(struct vring_virtqueue *vq,
>
> if (ctx)
> *ctx = state->indir_desc;
> +
Unnecessary changes.
Thanks
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