linux-kernel - Re: [PATCH] virtio_ring: switch to dma

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Message-ID: <524fb400-2325-f60b-7e03-15be01888afc@redhat.com>
Date:   Thu, 19 Apr 2018 19:48:24 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     linux-kernel@...r.kernel.org, Ohad Ben-Cohen <ohad@...ery.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        linux-remoteproc@...r.kernel.org, Jason Wang <jasowang@...hat.com>,
        virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH] virtio_ring: switch to dma_XX barriers for rpmsg

On 19/04/2018 19:46, Michael S. Tsirkin wrote:
>> This should be okay, but I wonder if there should be a virtio_wmb(...)
>> or an "if (weak_barriers) wmb()" before the "writel" in vm_notify
>> (drivers/virtio/virtio_mmio.c).
>>
>> Thanks,
>>
>> Paolo
> That one uses weak barriers AFAIK.
> 
> IIUC you mean rproc_virtio_notify.
> 
> I suspect it works because specific kick callbacks have a barrier internally.

Yes, that one.  At least keystone_rproc_kick doesn't seem to have a barrier.

Paolo