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Groups > linux.kernel > #1300279

Re: [PATCH v2 32/32] virtio_ring: use virt_store_mb

From "Michael S. Tsirkin" <mst@redhat.com>
Newsgroups linux.kernel
Subject Re: [PATCH v2 32/32] virtio_ring: use virt_store_mb
Date 2016-01-03 10:10 +0100
Message-ID <qMMPM-3p0-5@gated-at.bofh.it> (permalink)
References <qLQLL-8pu-3@gated-at.bofh.it> <qLQVs-8sN-11@gated-at.bofh.it> <qMbGz-5lD-49@gated-at.bofh.it>
Organization linux.* mail to news gateway

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On Fri, Jan 01, 2016 at 08:23:46PM +0300, Sergei Shtylyov wrote:
> Hello.
> 
> On 12/31/2015 10:09 PM, Michael S. Tsirkin wrote:
> 
> >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

Will fix, thanks!
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[PATCH v2 00/34] arch: barrier cleanup + barriers for virt "Michael S. Tsirkin" <mst@redhat.com> - 2015-12-31 20:10 +0100
  [PATCH v2 08/32] arm: reuse asm-generic/barrier.h "Michael S. Tsirkin" <mst@redhat.com> - 2015-12-31 20:10 +0100
    Re: [PATCH v2 08/32] arm: reuse asm-generic/barrier.h Russell King - ARM Linux <linux@arm.linux.org.uk> - 2016-01-02 12:30 +0100
  [PATCH v2 27/32] x86: define __smp_xxx "Michael S. Tsirkin" <mst@redhat.com> - 2015-12-31 20:10 +0100
  [PATCH v2 04/32] ia64: reuse asm-generic/barrier.h "Michael S. Tsirkin" <mst@redhat.com> - 2015-12-31 20:10 +0100
  [PATCH v2 22/32] s390: define __smp_xxx "Michael S. Tsirkin" <mst@redhat.com> - 2015-12-31 20:10 +0100
    Re: [PATCH v2 22/32] s390: define __smp_xxx Peter Zijlstra <peterz@infradead.org> - 2016-01-04 14:50 +0100
      Re: [PATCH v2 22/32] s390: define __smp_xxx "Michael S. Tsirkin" <mst@redhat.com> - 2016-01-04 21:20 +0100
        Re: [PATCH v2 22/32] s390: define __smp_xxx Martin Schwidefsky <schwidefsky@de.ibm.com> - 2016-01-05 09:20 +0100
          Re: [PATCH v2 22/32] s390: define __smp_xxx "Michael S. Tsirkin" <mst@redhat.com> - 2016-01-05 10:40 +0100
            Re: [PATCH v2 22/32] s390: define __smp_xxx Martin Schwidefsky <schwidefsky@de.ibm.com> - 2016-01-05 13:10 +0100
              Re: [PATCH v2 22/32] s390: define __smp_xxx "Michael S. Tsirkin" <mst@redhat.com> - 2016-01-05 14:10 +0100
                Re: [PATCH v2 22/32] s390: define __smp_xxx Martin Schwidefsky <schwidefsky@de.ibm.com> - 2016-01-05 15:30 +0100
            Re: [PATCH v2 22/32] s390: define __smp_xxx Christian Borntraeger <borntraeger@de.ibm.com> - 2016-01-05 16:50 +0100
              Re: [PATCH v2 22/32] s390: define __smp_xxx "Michael S. Tsirkin" <mst@redhat.com> - 2016-01-05 17:10 +0100
  [PATCH v2 15/32] powerpc: define __smp_xxx "Michael S. Tsirkin" <mst@redhat.com> - 2015-12-31 20:10 +0100
    Re: [PATCH v2 15/32] powerpc: define __smp_xxx Boqun Feng <boqun.feng@gmail.com> - 2016-01-05 02:40 +0100
      Re: [PATCH v2 15/32] powerpc: define __smp_xxx "Michael S. Tsirkin" <mst@redhat.com> - 2016-01-05 10:00 +0100
        Re: [PATCH v2 15/32] powerpc: define __smp_xxx Boqun Feng <boqun.feng@gmail.com> - 2016-01-05 11:00 +0100
          Re: [PATCH v2 15/32] powerpc: define __smp_xxx "Michael S. Tsirkin" <mst@redhat.com> - 2016-01-05 17:20 +0100
            Re: [PATCH v2 15/32] powerpc: define __smp_xxx Boqun Feng <boqun.feng@gmail.com> - 2016-01-06 03:00 +0100
              Re: [PATCH v2 15/32] powerpc: define __smp_xxx "Michael S. Tsirkin" <mst@redhat.com> - 2016-01-06 21:30 +0100
                Re: [PATCH v2 15/32] powerpc: define __smp_xxx Boqun Feng <boqun.feng@gmail.com> - 2016-01-07 01:50 +0100
  [PATCH v2 12/32] x86/um: reuse asm-generic/barrier.h "Michael S. Tsirkin" <mst@redhat.com> - 2015-12-31 20:10 +0100
    Re: [PATCH v2 12/32] x86/um: reuse asm-generic/barrier.h Richard Weinberger <richard@nod.at> - 2016-01-06 00:20 +0100
  [PATCH v2 10/32] metag: reuse asm-generic/barrier.h "Michael S. Tsirkin" <mst@redhat.com> - 2015-12-31 20:10 +0100
    Re: [PATCH v2 10/32] metag: reuse asm-generic/barrier.h James Hogan <james.hogan@imgtec.com> - 2016-01-05 00:30 +0100
  [PATCH v2 16/32] arm64: define __smp_xxx "Michael S. Tsirkin" <mst@redhat.com> - 2015-12-31 20:10 +0100
  [PATCH v2 03/32] ia64: rename nop->iosapic_nop "Michael S. Tsirkin" <mst@redhat.com> - 2015-12-31 20:10 +0100
  [PATCH v2 06/32] s390: reuse asm-generic/barrier.h "Michael S. Tsirkin" <mst@redhat.com> - 2015-12-31 20:10 +0100
    Re: [PATCH v2 06/32] s390: reuse asm-generic/barrier.h Peter Zijlstra <peterz@infradead.org> - 2016-01-04 14:30 +0100
      Re: [PATCH v2 06/32] s390: reuse asm-generic/barrier.h Martin Schwidefsky <schwidefsky@de.ibm.com> - 2016-01-04 16:10 +0100
        Re: [PATCH v2 06/32] s390: reuse asm-generic/barrier.h "Michael S. Tsirkin" <mst@redhat.com> - 2016-01-04 21:50 +0100
          Re: [PATCH v2 06/32] s390: reuse asm-generic/barrier.h Martin Schwidefsky <schwidefsky@de.ibm.com> - 2016-01-05 09:10 +0100
      Re: [PATCH v2 06/32] s390: reuse asm-generic/barrier.h "Michael S. Tsirkin" <mst@redhat.com> - 2016-01-04 21:40 +0100
  [PATCH v2 21/32] mips: define __smp_xxx "Michael S. Tsirkin" <mst@redhat.com> - 2015-12-31 20:20 +0100
  [PATCH v2 09/32] arm64: reuse asm-generic/barrier.h "Michael S. Tsirkin" <mst@redhat.com> - 2015-12-31 20:20 +0100
  [PATCH v2 32/32] virtio_ring: use virt_store_mb "Michael S. Tsirkin" <mst@redhat.com> - 2015-12-31 20:20 +0100
    Re: [PATCH v2 32/32] virtio_ring: use virt_store_mb Sergei Shtylyov <sergei.shtylyov@cogentembedded.com> - 2016-01-01 18:30 +0100
      Re: [PATCH v2 32/32] virtio_ring: use virt_store_mb "Michael S. Tsirkin" <mst@redhat.com> - 2016-01-03 10:10 +0100
  [PATCH v2 31/32] sh: support a 2-byte smp_store_mb "Michael S. Tsirkin" <mst@redhat.com> - 2015-12-31 20:20 +0100
    Re: [PATCH v2 31/32] sh: support a 2-byte smp_store_mb Peter Zijlstra <peterz@infradead.org> - 2016-01-04 15:10 +0100
    Re: [PATCH v2 31/32] sh: support a 2-byte smp_store_mb Rich Felker <dalias@libc.org> - 2016-01-06 00:40 +0100
      Re: [PATCH v2 31/32] sh: support a 2-byte smp_store_mb "Michael S. Tsirkin" <mst@redhat.com> - 2016-01-06 12:20 +0100
        Re: [PATCH v2 31/32] sh: support a 2-byte smp_store_mb Peter Zijlstra <peterz@infradead.org> - 2016-01-06 12:50 +0100
          Re: [PATCH v2 31/32] sh: support a 2-byte smp_store_mb "Michael S. Tsirkin" <mst@redhat.com> - 2016-01-06 13:00 +0100
            Re: [PATCH v2 31/32] sh: support a 2-byte smp_store_mb Peter Zijlstra <peterz@infradead.org> - 2016-01-06 15:40 +0100
              Re: [PATCH v2 31/32] sh: support a 2-byte smp_store_mb Rob Landley <rob@landley.net> - 2016-01-06 16:50 +0100
                Re: [PATCH v2 31/32] sh: support a 2-byte smp_store_mb Peter Zijlstra <peterz@infradead.org> - 2016-01-06 18:00 +0100
                Re: [PATCH v2 31/32] sh: support a 2-byte smp_store_mb Rob Landley <rob@landley.net> - 2016-01-06 21:30 +0100
                Re: [PATCH v2 31/32] sh: support a 2-byte smp_store_mb Geert Uytterhoeven <geert@linux-m68k.org> - 2016-01-06 20:00 +0100
              Re: [PATCH v2 31/32] sh: support a 2-byte smp_store_mb Rich Felker <dalias@libc.org> - 2016-01-06 19:30 +0100
                Re: [PATCH v2 31/32] sh: support a 2-byte smp_store_mb "Michael S. Tsirkin" <mst@redhat.com> - 2016-01-06 21:30 +0100
                Re: [PATCH v2 31/32] sh: support a 2-byte smp_store_mb Rich Felker <dalias@libc.org> - 2016-01-07 01:00 +0100
                Re: [PATCH v2 31/32] sh: support a 2-byte smp_store_mb Peter Zijlstra <peterz@infradead.org> - 2016-01-07 14:40 +0100
                Re: [PATCH v2 31/32] sh: support a 2-byte smp_store_mb Rich Felker <dalias@libc.org> - 2016-01-07 20:10 +0100
                Re: [PATCH v2 31/32] sh: support a 2-byte smp_store_mb "Michael S. Tsirkin" <mst@redhat.com> - 2016-01-07 17:00 +0100
                Re: [PATCH v2 31/32] sh: support a 2-byte smp_store_mb "Michael S. Tsirkin" <mst@redhat.com> - 2016-01-07 18:50 +0100
                Re: [PATCH v2 31/32] sh: support a 2-byte smp_store_mb Rich Felker <dalias@libc.org> - 2016-01-07 20:20 +0100
                Re: [PATCH v2 31/32] sh: support a 2-byte smp_store_mb "Michael S. Tsirkin" <mst@redhat.com> - 2016-01-07 23:50 +0100
                Re: [PATCH v2 31/32] sh: support a 2-byte smp_store_mb Rich Felker <dalias@libc.org> - 2016-01-08 05:30 +0100
                Re: [PATCH v2 31/32] sh: support a 2-byte smp_store_mb "Michael S. Tsirkin" <mst@redhat.com> - 2016-01-08 08:30 +0100
                Re: [PATCH v2 31/32] sh: support a 2-byte smp_store_mb "Michael S. Tsirkin" <mst@redhat.com> - 2016-01-06 23:20 +0100
  [PATCH v2 33/34] xenbus: use virt_xxx barriers "Michael S. Tsirkin" <mst@redhat.com> - 2015-12-31 20:20 +0100
    Re: [Xen-devel] [PATCH v2 33/34] xenbus: use virt_xxx barriers David Vrabel <david.vrabel@citrix.com> - 2016-01-04 12:40 +0100
    Re: [PATCH v2 33/34] xenbus: use virt_xxx barriers Stefano Stabellini <stefano.stabellini@eu.citrix.com> - 2016-01-04 13:10 +0100
    Re: [PATCH v2 33/34] xenbus: use virt_xxx barriers Peter Zijlstra <peterz@infradead.org> - 2016-01-04 15:20 +0100
  [PATCH v2 26/32] xtensa: define __smp_xxx "Michael S. Tsirkin" <mst@redhat.com> - 2015-12-31 20:20 +0100
  [PATCH v2 34/34] xen/io: use virt_xxx barriers "Michael S. Tsirkin" <mst@redhat.com> - 2015-12-31 20:20 +0100
    Re: [Xen-devel] [PATCH v2 34/34] xen/io: use virt_xxx barriers David Vrabel <david.vrabel@citrix.com> - 2016-01-04 12:40 +0100
    Re: [PATCH v2 34/34] xen/io: use virt_xxx barriers Stefano Stabellini <stefano.stabellini@eu.citrix.com> - 2016-01-04 13:10 +0100
  [PATCH v2 02/32] asm-generic: guard smp_store_release/load_acquire "Michael S. Tsirkin" <mst@redhat.com> - 2015-12-31 20:20 +0100
  [PATCH v2 30/32] virtio_ring: update weak barriers to use __smp_xxx "Michael S. Tsirkin" <mst@redhat.com> - 2016-01-01 10:40 +0100
    Re: [PATCH v2 30/32] virtio_ring: update weak barriers to use  __smp_xxx "Michael S. Tsirkin" <mst@redhat.com> - 2016-01-01 11:30 +0100

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