Re: [PATCH v2 32/32] virtio_ring: use virt_store_mb
From: Sergei Shtylyov <hidden>
Date: 2016-01-01 17:23:56
Also in:
linux-arm-kernel, linux-mips, linux-s390, linux-sh, linux-um, linuxppc-dev, lkml, sparclinux, virtualization
Hello. On 12/31/2015 10:09 PM, Michael S. Tsirkin wrote:
quoted hunk ↗ jump to hunk
We need a full barrier after writing out event index, using virt_store_mb there seems better than open-coding. As usual, we need a wrapper to account for strong barriers. It's tempting to use this in vhost as well, for that, we'll need a variant of smp_store_mb that works on __user pointers. Signed-off-by: Michael S. Tsirkin <mst@redhat.com> --- include/linux/virtio_ring.h | 12 ++++++++++++ drivers/virtio/virtio_ring.c | 15 +++++++++------ 2 files changed, 21 insertions(+), 6 deletions(-)diff --git a/include/linux/virtio_ring.h b/include/linux/virtio_ring.h index f3fa55b..3a74d91 100644 --- a/include/linux/virtio_ring.h +++ b/include/linux/virtio_ring.h@@ -45,6 +45,18 @@ static inline void virtio_wmb(bool weak_barriers) wmb(); } +static inline void virtio_store_mb(bool weak_barriers, + __virtio16 *p, __virtio16 v) +{ + if (weak_barriers) + virt_store_mb(*p, v); + else + {
The kernel coding style dictates:
if (weak_barriers) {
virt_store_mb(*p, v);
} else {
+ WRITE_ONCE(*p, v); + mb(); + } +} +
[...] MBR, Sergei