RE: [RFC 06/27] vhost: don't dump unneeded pages with IOTLB

["Xia, Chenbo" <chenbo.xia@intel.com>]

> -----Original Message-----
> From: Maxime Coquelin <maxime.coquelin@redhat.com>
> Sent: Friday, March 31, 2023 11:43 PM
> To: dev@dpdk.org; david.marchand@redhat.com; Xia, Chenbo
> <chenbo.xia@intel.com>; mkp@redhat.com; fbl@redhat.com;
> jasowang@redhat.com; Liang, Cunming <cunming.liang@intel.com>; Xie, Yongji
> <xieyongji@bytedance.com>; echaudro@redhat.com; eperezma@redhat.com;
> amorenoz@redhat.com
> Cc: Maxime Coquelin <maxime.coquelin@redhat.com>; stable@dpdk.org
> Subject: [RFC 06/27] vhost: don't dump unneeded pages with IOTLB
> 
> On IOTLB entry removal, previous fixes took care of not
> marking pages shared with other IOTLB entries as DONTDUMP.
> 
> However, if an IOTLB entry is spanned on multiple pages,
> the other pages were kept as DODUMP while they might not
> have been shared with other entries, increasing needlessly
> the coredump size.
> 
> This patch addresses this issue by excluding only the
> shared pages from madvise's DONTDUMP.
> 
> Fixes: dea092d0addb ("vhost: fix madvise arguments alignment")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
> ---
>  lib/vhost/iotlb.c | 21 ++++++++++++++-------
>  1 file changed, 14 insertions(+), 7 deletions(-)
> 
> diff --git a/lib/vhost/iotlb.c b/lib/vhost/iotlb.c
> index d919f74704..f598c0a8c4 100644
> --- a/lib/vhost/iotlb.c
> +++ b/lib/vhost/iotlb.c
> @@ -54,16 +54,23 @@ static void
>  vhost_user_iotlb_clear_dump(struct virtio_net *dev, struct
> vhost_iotlb_entry *node,
>  		struct vhost_iotlb_entry *prev, struct vhost_iotlb_entry *next)
>  {
> -	uint64_t align;
> +	uint64_t align, start, end;
> +
> +	start = node->uaddr;
> +	end = node->uaddr + node->size;
> 
>  	align = hua_to_alignment(dev->mem, (void *)(uintptr_t)node->uaddr);
> 
> -	/* Don't disable coredump if the previous node is in the same page
> */
> -	if (!vhost_user_iotlb_share_page(prev, node, align)) {
> -		/* Don't disable coredump if the next node is in the same page
> */
> -		if (!vhost_user_iotlb_share_page(node, next, align))
> -			mem_set_dump((void *)(uintptr_t)node->uaddr, node->size,
> false, align);
> -	}
> +	/* Skip first page if shared with previous entry. */
> +	if (vhost_user_iotlb_share_page(prev, node, align))
> +		start = RTE_ALIGN_CEIL(start, align);
> +
> +	/* Skip last page if shared with next entry. */
> +	if (vhost_user_iotlb_share_page(node, next, align))
> +		end = RTE_ALIGN_FLOOR(end, align);
> +
> +	if (end > start)
> +		mem_set_dump((void *)(uintptr_t)start, end - start, false,
> align);
>  }
> 
>  static struct vhost_iotlb_entry *
> --
> 2.39.2

Reviewed-by: Chenbo Xia <chenbo.xia@intel.com>