Hi Jason,
Would you mind helping confirm if it resolves your concern in v2?
Thank you very much!
Dongli Zhang
On 4/2/25 11:29 PM, Dongli Zhang wrote:
> Currently, the only user of vhost_log_write() is vhost-net. The 'len'
> argument prevents logging of pages that are not tainted by the RX path.
>
> Adjustments are needed since more drivers (i.e. vhost-scsi) begin using
> vhost_log_write(). So far vhost-net RX path may only partially use pages
> shared via the last vring descriptor. Unlike vhost-net, vhost-scsi always
> logs all pages shared via vring descriptors. To accommodate this,
> use (len == U64_MAX) to indicate whether the driver would log all pages of
> vring descriptors, or only pages that are tainted by the driver.
>
> In addition, removes BUG().
>
> Suggested-by: Joao Martins <joao.m.martins@xxxxxxxxxx>
> Signed-off-by: Dongli Zhang <dongli.zhang@xxxxxxxxxx>
> ---
> Changed since v2:
> - Document parameters of vhost_log_write().
> - Use (len == U64_MAX) to indicate whether log all pages, instead of
> introducing a new parameter.
>
> drivers/vhost/vhost.c | 28 ++++++++++++++++++++--------
> 1 file changed, 20 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> index 9ac25d08f473..494b3da5423a 100644
> --- a/drivers/vhost/vhost.c
> +++ b/drivers/vhost/vhost.c
> @@ -2304,6 +2304,19 @@ static int log_used(struct vhost_virtqueue *vq, u64 used_offset, u64 len)
> return 0;
> }
>
> +/*
> + * vhost_log_write() - Log in dirty page bitmap
> + * @vq: vhost virtqueue.
> + * @log: Array of dirty memory in GPA.
> + * @log_num: Size of vhost_log arrary.
> + * @len: The total length of memory buffer to log in the dirty bitmap.
> + * Some drivers may only partially use pages shared via the last
> + * vring descriptor (i.e. vhost-net RX buffer).
> + * Use (len == U64_MAX) to indicate the driver would log all
> + * pages of vring descriptors.
> + * @iov: Array of dirty memory in HVA.
> + * @count: Size of iovec array.
> + */
> int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log,
> unsigned int log_num, u64 len, struct iovec *iov, int count)
> {
> @@ -2327,15 +2340,14 @@ int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log,
> r = log_write(vq->log_base, log[i].addr, l);
> if (r < 0)
> return r;
> - len -= l;
> - if (!len) {
> - if (vq->log_ctx)
> - eventfd_signal(vq->log_ctx);
> - return 0;
> - }
> +
> + if (len != U64_MAX)
> + len -= l;
> }
> - /* Length written exceeds what we have stored. This is a bug. */
> - BUG();
> +
> + if (vq->log_ctx)
> + eventfd_signal(vq->log_ctx);
> +
> return 0;
> }
> EXPORT_SYMBOL_GPL(vhost_log_write);
