| Message ID | 1451572003-2440-35-git-send-email-mst@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 31/12/15 19:10, Michael S. Tsirkin wrote: > include/xen/interface/io/ring.h uses > full memory barriers to communicate with the other side. > > For guests compiled with CONFIG_SMP, smp_wmb and smp_mb > would be sufficient, so mb() and wmb() here are only needed if > a non-SMP guest runs on an SMP host. > > Switch to virt_xxx barriers which serve this exact purpose. Acked-by: David Vrabel <david.vrabel@citrix.com> David
On Thu, 31 Dec 2015, Michael S. Tsirkin wrote: > include/xen/interface/io/ring.h uses > full memory barriers to communicate with the other side. > > For guests compiled with CONFIG_SMP, smp_wmb and smp_mb > would be sufficient, so mb() and wmb() here are only needed if > a non-SMP guest runs on an SMP host. > > Switch to virt_xxx barriers which serve this exact purpose. > > Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Reviewed-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com> > include/xen/interface/io/ring.h | 16 ++++++++-------- > 1 file changed, 8 insertions(+), 8 deletions(-) > > diff --git a/include/xen/interface/io/ring.h b/include/xen/interface/io/ring.h > index 7dc685b..21f4fbd 100644 > --- a/include/xen/interface/io/ring.h > +++ b/include/xen/interface/io/ring.h > @@ -208,12 +208,12 @@ struct __name##_back_ring { \ > > > #define RING_PUSH_REQUESTS(_r) do { \ > - wmb(); /* back sees requests /before/ updated producer index */ \ > + virt_wmb(); /* back sees requests /before/ updated producer index */ \ > (_r)->sring->req_prod = (_r)->req_prod_pvt; \ > } while (0) > > #define RING_PUSH_RESPONSES(_r) do { \ > - wmb(); /* front sees responses /before/ updated producer index */ \ > + virt_wmb(); /* front sees responses /before/ updated producer index */ \ > (_r)->sring->rsp_prod = (_r)->rsp_prod_pvt; \ > } while (0) > > @@ -250,9 +250,9 @@ struct __name##_back_ring { \ > #define RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(_r, _notify) do { \ > RING_IDX __old = (_r)->sring->req_prod; \ > RING_IDX __new = (_r)->req_prod_pvt; \ > - wmb(); /* back sees requests /before/ updated producer index */ \ > + virt_wmb(); /* back sees requests /before/ updated producer index */ \ > (_r)->sring->req_prod = __new; \ > - mb(); /* back sees new requests /before/ we check req_event */ \ > + virt_mb(); /* back sees new requests /before/ we check req_event */ \ > (_notify) = ((RING_IDX)(__new - (_r)->sring->req_event) < \ > (RING_IDX)(__new - __old)); \ > } while (0) > @@ -260,9 +260,9 @@ struct __name##_back_ring { \ > #define RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(_r, _notify) do { \ > RING_IDX __old = (_r)->sring->rsp_prod; \ > RING_IDX __new = (_r)->rsp_prod_pvt; \ > - wmb(); /* front sees responses /before/ updated producer index */ \ > + virt_wmb(); /* front sees responses /before/ updated producer index */ \ > (_r)->sring->rsp_prod = __new; \ > - mb(); /* front sees new responses /before/ we check rsp_event */ \ > + virt_mb(); /* front sees new responses /before/ we check rsp_event */ \ > (_notify) = ((RING_IDX)(__new - (_r)->sring->rsp_event) < \ > (RING_IDX)(__new - __old)); \ > } while (0) > @@ -271,7 +271,7 @@ struct __name##_back_ring { \ > (_work_to_do) = RING_HAS_UNCONSUMED_REQUESTS(_r); \ > if (_work_to_do) break; \ > (_r)->sring->req_event = (_r)->req_cons + 1; \ > - mb(); \ > + virt_mb(); \ > (_work_to_do) = RING_HAS_UNCONSUMED_REQUESTS(_r); \ > } while (0) > > @@ -279,7 +279,7 @@ struct __name##_back_ring { \ > (_work_to_do) = RING_HAS_UNCONSUMED_RESPONSES(_r); \ > if (_work_to_do) break; \ > (_r)->sring->rsp_event = (_r)->rsp_cons + 1; \ > - mb(); \ > + virt_mb(); \ > (_work_to_do) = RING_HAS_UNCONSUMED_RESPONSES(_r); \ > } while (0) > > -- > MST >
diff --git a/include/xen/interface/io/ring.h b/include/xen/interface/io/ring.h index 7dc685b..21f4fbd 100644 --- a/include/xen/interface/io/ring.h +++ b/include/xen/interface/io/ring.h @@ -208,12 +208,12 @@ struct __name##_back_ring { \ #define RING_PUSH_REQUESTS(_r) do { \ - wmb(); /* back sees requests /before/ updated producer index */ \ + virt_wmb(); /* back sees requests /before/ updated producer index */ \ (_r)->sring->req_prod = (_r)->req_prod_pvt; \ } while (0) #define RING_PUSH_RESPONSES(_r) do { \ - wmb(); /* front sees responses /before/ updated producer index */ \ + virt_wmb(); /* front sees responses /before/ updated producer index */ \ (_r)->sring->rsp_prod = (_r)->rsp_prod_pvt; \ } while (0) @@ -250,9 +250,9 @@ struct __name##_back_ring { \ #define RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(_r, _notify) do { \ RING_IDX __old = (_r)->sring->req_prod; \ RING_IDX __new = (_r)->req_prod_pvt; \ - wmb(); /* back sees requests /before/ updated producer index */ \ + virt_wmb(); /* back sees requests /before/ updated producer index */ \ (_r)->sring->req_prod = __new; \ - mb(); /* back sees new requests /before/ we check req_event */ \ + virt_mb(); /* back sees new requests /before/ we check req_event */ \ (_notify) = ((RING_IDX)(__new - (_r)->sring->req_event) < \ (RING_IDX)(__new - __old)); \ } while (0) @@ -260,9 +260,9 @@ struct __name##_back_ring { \ #define RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(_r, _notify) do { \ RING_IDX __old = (_r)->sring->rsp_prod; \ RING_IDX __new = (_r)->rsp_prod_pvt; \ - wmb(); /* front sees responses /before/ updated producer index */ \ + virt_wmb(); /* front sees responses /before/ updated producer index */ \ (_r)->sring->rsp_prod = __new; \ - mb(); /* front sees new responses /before/ we check rsp_event */ \ + virt_mb(); /* front sees new responses /before/ we check rsp_event */ \ (_notify) = ((RING_IDX)(__new - (_r)->sring->rsp_event) < \ (RING_IDX)(__new - __old)); \ } while (0) @@ -271,7 +271,7 @@ struct __name##_back_ring { \ (_work_to_do) = RING_HAS_UNCONSUMED_REQUESTS(_r); \ if (_work_to_do) break; \ (_r)->sring->req_event = (_r)->req_cons + 1; \ - mb(); \ + virt_mb(); \ (_work_to_do) = RING_HAS_UNCONSUMED_REQUESTS(_r); \ } while (0) @@ -279,7 +279,7 @@ struct __name##_back_ring { \ (_work_to_do) = RING_HAS_UNCONSUMED_RESPONSES(_r); \ if (_work_to_do) break; \ (_r)->sring->rsp_event = (_r)->rsp_cons + 1; \ - mb(); \ + virt_mb(); \ (_work_to_do) = RING_HAS_UNCONSUMED_RESPONSES(_r); \ } while (0)
include/xen/interface/io/ring.h uses full memory barriers to communicate with the other side. For guests compiled with CONFIG_SMP, smp_wmb and smp_mb would be sufficient, so mb() and wmb() here are only needed if a non-SMP guest runs on an SMP host. Switch to virt_xxx barriers which serve this exact purpose. Signed-off-by: Michael S. Tsirkin <mst@redhat.com> --- include/xen/interface/io/ring.h | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-)