[RFC 05/27] vhost: add helper for IOTLB entries shared page check

[Xia, Chenbo]

> -----Original Message-----
> From: Maxime Coquelin <maxime.coquelin at redhat.com>
> Sent: Friday, March 31, 2023 11:43 PM
> To: dev at dpdk.org; david.marchand at redhat.com; Xia, Chenbo
> <chenbo.xia at intel.com>; mkp at redhat.com; fbl at redhat.com;
> jasowang at redhat.com; Liang, Cunming <cunming.liang at intel.com>; Xie, Yongji
> <xieyongji at bytedance.com>; echaudro at redhat.com; eperezma at redhat.com;
> amorenoz at redhat.com
> Cc: Maxime Coquelin <maxime.coquelin at redhat.com>
> Subject: [RFC 05/27] vhost: add helper for IOTLB entries shared page check
> 
> This patch introduces a helper to check whether two IOTLB
> entries share a page.
> 
> Signed-off-by: Maxime Coquelin <maxime.coquelin at redhat.com>
> ---
>  lib/vhost/iotlb.c | 25 ++++++++++++++++++++-----
>  1 file changed, 20 insertions(+), 5 deletions(-)
> 
> diff --git a/lib/vhost/iotlb.c b/lib/vhost/iotlb.c
> index e8f1cb661e..d919f74704 100644
> --- a/lib/vhost/iotlb.c
> +++ b/lib/vhost/iotlb.c
> @@ -23,6 +23,23 @@ struct vhost_iotlb_entry {
> 
>  #define IOTLB_CACHE_SIZE 2048
> 
> +static bool
> +vhost_user_iotlb_share_page(struct vhost_iotlb_entry *a, struct
> vhost_iotlb_entry *b,
> +		uint64_t align)
> +{
> +	uint64_t a_end, b_start;
> +
> +	if (a == NULL || b == NULL)
> +		return false;
> +
> +	/* Assumes entry a lower than entry b */
> +	RTE_ASSERT(a->uaddr < b->uaddr);
> +	a_end = RTE_ALIGN_CEIL(a->uaddr + a->size, align);
> +	b_start = RTE_ALIGN_FLOOR(b->uaddr, align);
> +
> +	return a_end > b_start;
> +}
> +
>  static void
>  vhost_user_iotlb_set_dump(struct virtio_net *dev, struct
> vhost_iotlb_entry *node)
>  {
> @@ -37,16 +54,14 @@ 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, mask;
> +	uint64_t align;
> 
>  	align = hua_to_alignment(dev->mem, (void *)(uintptr_t)node->uaddr);
> -	mask = ~(align - 1);
> 
>  	/* Don't disable coredump if the previous node is in the same page
> */
> -	if (prev == NULL || (node->uaddr & mask) != ((prev->uaddr + prev-
> >size - 1) & mask)) {
> +	if (!vhost_user_iotlb_share_page(prev, node, align)) {
>  		/* Don't disable coredump if the next node is in the same page
> */
> -		if (next == NULL ||
> -				((node->uaddr + node->size - 1) & mask) != (next-
> >uaddr & mask))
> +		if (!vhost_user_iotlb_share_page(node, next, align))
>  			mem_set_dump((void *)(uintptr_t)node->uaddr, node->size,
> false, align);
>  	}
>  }
> --
> 2.39.2

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