From ac3d5ac277352fe6e27809286768e9f1f8aa388d Mon Sep 17 00:00:00 2001 From: Paul Durrant Date: Mon, 23 Dec 2013 09:27:17 +0000 Subject: xen-netback: fix guest-receive-side array sizes The sizes chosen for the metadata and grant_copy_op arrays on the guest receive size are wrong; - The meta array is needlessly twice the ring size, when we only ever consume a single array element per RX ring slot - The grant_copy_op array is way too small. It's sized based on a bogus assumption: that at most two copy ops will be used per ring slot. This may have been true at some point in the past but it's clear from looking at start_new_rx_buffer() that a new ring slot is only consumed if a frag would overflow the current slot (plus some other conditions) so the actual limit is MAX_SKB_FRAGS grant_copy_ops per ring slot. This patch fixes those two sizing issues and, because grant_copy_ops grows so much, it pulls it out into a separate chunk of vmalloc()ed memory. Signed-off-by: Paul Durrant Acked-by: Wei Liu Cc: Ian Campbell Cc: David Vrabel Signed-off-by: David S. Miller --- drivers/net/xen-netback/common.h | 19 +++++++++++++------ 1 file changed, 13 insertions(+), 6 deletions(-) (limited to 'drivers/net/xen-netback/common.h') diff --git a/drivers/net/xen-netback/common.h b/drivers/net/xen-netback/common.h index 08ae01b41c8..c47794b9d42 100644 --- a/drivers/net/xen-netback/common.h +++ b/drivers/net/xen-netback/common.h @@ -101,6 +101,13 @@ struct xenvif_rx_meta { #define MAX_PENDING_REQS 256 +/* It's possible for an skb to have a maximal number of frags + * but still be less than MAX_BUFFER_OFFSET in size. Thus the + * worst-case number of copy operations is MAX_SKB_FRAGS per + * ring slot. + */ +#define MAX_GRANT_COPY_OPS (MAX_SKB_FRAGS * XEN_NETIF_RX_RING_SIZE) + struct xenvif { /* Unique identifier for this interface. */ domid_t domid; @@ -143,13 +150,13 @@ struct xenvif { */ RING_IDX rx_req_cons_peek; - /* Given MAX_BUFFER_OFFSET of 4096 the worst case is that each - * head/fragment page uses 2 copy operations because it - * straddles two buffers in the frontend. - */ - struct gnttab_copy grant_copy_op[2*XEN_NETIF_RX_RING_SIZE]; - struct xenvif_rx_meta meta[2*XEN_NETIF_RX_RING_SIZE]; + /* This array is allocated seperately as it is large */ + struct gnttab_copy *grant_copy_op; + /* We create one meta structure per ring request we consume, so + * the maximum number is the same as the ring size. + */ + struct xenvif_rx_meta meta[XEN_NETIF_RX_RING_SIZE]; u8 fe_dev_addr[6]; -- cgit v1.2.3-70-g09d2