Re: [PATCH 5/6] block/nvme: Align block pages queue to host page size

[David Gibson]

On Mon, May 04, 2020 at 11:46:40AM +0200, Philippe Mathieu-Daudé wrote:
> In nvme_create_queue_pair() we create a page list using
> qemu_blockalign(), then map it with qemu_vfio_dma_map():
> 
>   q->prp_list_pages = qemu_blockalign0(bs, s->page_size * NVME_QUEUE_SIZE);
>   r = qemu_vfio_dma_map(s->vfio, q->prp_list_pages,
>                         s->page_size * NVME_QUEUE_SIZE, ...);
> 
> With:
> 
>   s->page_size = MAX(4096, 1 << (12 + ((cap >> 48) & 0xF)));
> 
> The qemu_vfio_dma_map() documentation says "The caller need
> to make sure the area is aligned to page size". While we use
> multiple s->page_size as alignment, it might be not sufficient
> on some hosts. Use the qemu_real_host_page_size value to be
> sure the host alignment is respected.
> 
> Signed-off-by: Philippe Mathieu-Daudé <address@hidden>

Reviewed-by: David Gibson <address@hidden>

> ---
> Cc: Cédric Le Goater <address@hidden>
> Cc: David Gibson <address@hidden>
> Cc: Laurent Vivier <address@hidden>
> ---
>  block/nvme.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/block/nvme.c b/block/nvme.c
> index 7b7c0cc5d6..bde0d28b39 100644
> --- a/block/nvme.c
> +++ b/block/nvme.c
> @@ -627,7 +627,7 @@ static int nvme_init(BlockDriverState *bs, const char 
> *device, int namespace,
>  
>      s->page_size = MAX(4096, 1 << (12 + ((cap >> 48) & 0xF)));
>      s->doorbell_scale = (4 << (((cap >> 32) & 0xF))) / sizeof(uint32_t);
> -    bs->bl.opt_mem_alignment = s->page_size;
> +    bs->bl.opt_mem_alignment = MAX(qemu_real_host_page_size, s->page_size);
>      timeout_ms = MIN(500 * ((cap >> 24) & 0xFF), 30000);
>  
>      /* Reset device to get a clean state. */

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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