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Date: Mon, 1 Feb 2021 14:03:39 +0800
From: Jason Wang <jasowang@...hat.com>
To: Stefano Garzarella <sgarzare@...hat.com>,
virtualization@...ts.linux-foundation.org
Cc: Xie Yongji <xieyongji@...edance.com>,
"Michael S. Tsirkin" <mst@...hat.com>,
Laurent Vivier <lvivier@...hat.com>,
Stefan Hajnoczi <stefanha@...hat.com>,
linux-kernel@...r.kernel.org, Max Gurtovoy <mgurtovoy@...dia.com>,
kvm@...r.kernel.org
Subject: Re: [PATCH RFC v2 09/10] vdpa_sim_blk: implement ramdisk behaviour
On 2021/1/28 下午10:41, Stefano Garzarella wrote:
> The previous implementation wrote only the status of each request.
> This patch implements a more accurate block device simulator,
> providing a ramdisk-like behavior.
>
> Signed-off-by: Stefano Garzarella <sgarzare@...hat.com>
> ---
> v2:
> - used %zd %zx to print size_t and ssize_t variables in dev_err()
> - removed unnecessary new line [Jason]
> - moved VIRTIO_BLK_T_GET_ID in another patch [Jason]
> - used push/pull instead of write/read terminology
> - added vdpasim_blk_check_range() to avoid overflows [Stefan]
> - use vdpasim*_to_cpu instead of le*_to_cpu
> - used vringh_kiov_length() helper [Jason]
Acked-by: Jason Wang <jasowang@...hat.com>
> ---
> drivers/vdpa/vdpa_sim/vdpa_sim_blk.c | 164 ++++++++++++++++++++++++---
> 1 file changed, 146 insertions(+), 18 deletions(-)
>
> diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c b/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c
> index 999f9ca0b628..fc47e8320358 100644
> --- a/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c
> +++ b/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c
> @@ -3,6 +3,7 @@
> * VDPA simulator for block device.
> *
> * Copyright (c) 2020, Mellanox Technologies. All rights reserved.
> + * Copyright (c) 2021, Red Hat Inc. All rights reserved.
> *
> */
>
> @@ -13,6 +14,7 @@
> #include <linux/sched.h>
> #include <linux/vringh.h>
> #include <linux/vdpa.h>
> +#include <linux/blkdev.h>
> #include <uapi/linux/virtio_blk.h>
>
> #include "vdpa_sim.h"
> @@ -36,10 +38,151 @@
>
> static struct vdpasim *vdpasim_blk_dev;
>
> +static bool vdpasim_blk_check_range(u64 start_sector, size_t range_size)
> +{
> + u64 range_sectors = range_size >> SECTOR_SHIFT;
> +
> + if (range_size > VDPASIM_BLK_SIZE_MAX * VDPASIM_BLK_SEG_MAX)
> + return false;
> +
> + if (start_sector > VDPASIM_BLK_CAPACITY)
> + return false;
> +
> + if (range_sectors > VDPASIM_BLK_CAPACITY - start_sector)
> + return false;
> +
> + return true;
> +}
> +
> +/* Returns 'true' if the request is handled (with or without an I/O error)
> + * and the status is correctly written in the last byte of the 'in iov',
> + * 'false' otherwise.
> + */
> +static bool vdpasim_blk_handle_req(struct vdpasim *vdpasim,
> + struct vdpasim_virtqueue *vq)
> +{
> + size_t pushed = 0, to_pull, to_push;
> + struct virtio_blk_outhdr hdr;
> + ssize_t bytes;
> + loff_t offset;
> + u64 sector;
> + u8 status;
> + u32 type;
> + int ret;
> +
> + ret = vringh_getdesc_iotlb(&vq->vring, &vq->out_iov, &vq->in_iov,
> + &vq->head, GFP_ATOMIC);
> + if (ret != 1)
> + return false;
> +
> + if (vq->out_iov.used < 1 || vq->in_iov.used < 1) {
> + dev_err(&vdpasim->vdpa.dev, "missing headers - out_iov: %u in_iov %u\n",
> + vq->out_iov.used, vq->in_iov.used);
> + return false;
> + }
> +
> + if (vq->in_iov.iov[vq->in_iov.used - 1].iov_len < 1) {
> + dev_err(&vdpasim->vdpa.dev, "request in header too short\n");
> + return false;
> + }
> +
> + /* The last byte is the status and we checked if the last iov has
> + * enough room for it.
> + */
> + to_push = vringh_kiov_length(&vq->in_iov) - 1;
> +
> + to_pull = vringh_kiov_length(&vq->out_iov);
> +
> + bytes = vringh_iov_pull_iotlb(&vq->vring, &vq->out_iov, &hdr,
> + sizeof(hdr));
> + if (bytes != sizeof(hdr)) {
> + dev_err(&vdpasim->vdpa.dev, "request out header too short\n");
> + return false;
> + }
> +
> + to_pull -= bytes;
> +
> + type = vdpasim32_to_cpu(vdpasim, hdr.type);
> + sector = vdpasim64_to_cpu(vdpasim, hdr.sector);
> + offset = sector << SECTOR_SHIFT;
> + status = VIRTIO_BLK_S_OK;
> +
> + switch (type) {
> + case VIRTIO_BLK_T_IN:
> + if (!vdpasim_blk_check_range(sector, to_push)) {
> + dev_err(&vdpasim->vdpa.dev,
> + "reading over the capacity - offset: 0x%llx len: 0x%zx\n",
> + offset, to_push);
> + status = VIRTIO_BLK_S_IOERR;
> + break;
> + }
> +
> + bytes = vringh_iov_push_iotlb(&vq->vring, &vq->in_iov,
> + vdpasim->buffer + offset,
> + to_push);
> + if (bytes < 0) {
> + dev_err(&vdpasim->vdpa.dev,
> + "vringh_iov_push_iotlb() error: %zd offset: 0x%llx len: 0x%zx\n",
> + bytes, offset, to_push);
> + status = VIRTIO_BLK_S_IOERR;
> + break;
> + }
> +
> + pushed += bytes;
> + break;
> +
> + case VIRTIO_BLK_T_OUT:
> + if (!vdpasim_blk_check_range(sector, to_pull)) {
> + dev_err(&vdpasim->vdpa.dev,
> + "writing over the capacity - offset: 0x%llx len: 0x%zx\n",
> + offset, to_pull);
> + status = VIRTIO_BLK_S_IOERR;
> + break;
> + }
> +
> + bytes = vringh_iov_pull_iotlb(&vq->vring, &vq->out_iov,
> + vdpasim->buffer + offset,
> + to_pull);
> + if (bytes < 0) {
> + dev_err(&vdpasim->vdpa.dev,
> + "vringh_iov_pull_iotlb() error: %zd offset: 0x%llx len: 0x%zx\n",
> + bytes, offset, to_pull);
> + status = VIRTIO_BLK_S_IOERR;
> + break;
> + }
> + break;
> +
> + default:
> + dev_warn(&vdpasim->vdpa.dev,
> + "Unsupported request type %d\n", type);
> + status = VIRTIO_BLK_S_IOERR;
> + break;
> + }
> +
> + /* If some operations fail, we need to skip the remaining bytes
> + * to put the status in the last byte
> + */
> + if (to_push - pushed > 0)
> + vringh_kiov_advance(&vq->in_iov, to_push - pushed);
> +
> + /* Last byte is the status */
> + bytes = vringh_iov_push_iotlb(&vq->vring, &vq->in_iov, &status, 1);
> + if (bytes != 1)
> + return false;
> +
> + pushed += bytes;
> +
> + /* Make sure data is wrote before advancing index */
> + smp_wmb();
> +
> + vringh_complete_iotlb(&vq->vring, vq->head, pushed);
> +
> + return true;
> +}
> +
> static void vdpasim_blk_work(struct work_struct *work)
> {
> struct vdpasim *vdpasim = container_of(work, struct vdpasim, work);
> - u8 status = VIRTIO_BLK_S_OK;
> int i;
>
> spin_lock(&vdpasim->lock);
> @@ -53,22 +196,7 @@ static void vdpasim_blk_work(struct work_struct *work)
> if (!vq->ready)
> continue;
>
> - while (vringh_getdesc_iotlb(&vq->vring, &vq->out_iov,
> - &vq->in_iov, &vq->head,
> - GFP_ATOMIC) > 0) {
> - int write;
> -
> - vq->in_iov.i = vq->in_iov.used - 1;
> - write = vringh_iov_push_iotlb(&vq->vring, &vq->in_iov,
> - &status, 1);
> - if (write <= 0)
> - break;
> -
> - /* Make sure data is wrote before advancing index */
> - smp_wmb();
> -
> - vringh_complete_iotlb(&vq->vring, vq->head, write);
> -
> + while (vdpasim_blk_handle_req(vdpasim, vq)) {
> /* Make sure used is visible before rasing the interrupt. */
> smp_wmb();
>
> @@ -109,7 +237,7 @@ static int __init vdpasim_blk_init(void)
> dev_attr.config_size = sizeof(struct virtio_blk_config);
> dev_attr.get_config = vdpasim_blk_get_config;
> dev_attr.work_fn = vdpasim_blk_work;
> - dev_attr.buffer_size = PAGE_SIZE;
> + dev_attr.buffer_size = VDPASIM_BLK_CAPACITY << SECTOR_SHIFT;
>
> vdpasim_blk_dev = vdpasim_create(&dev_attr);
> if (IS_ERR(vdpasim_blk_dev)) {
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