Re: [RFC] virtio: use mandatory barriers for remote processor vdevs
From: Ohad Ben-Cohen
Date: Wed Nov 30 2011 - 11:24:39 EST
On Wed, Nov 30, 2011 at 6:15 PM, Michael S. Tsirkin <mst@xxxxxxxxxx> wrote:
> How are the rings mapped? normal memory, right?
No, device memory.
> We allocate them with plan alloc_pages_exact in virtio_pci.c ...
I'm not using virtio_pci.c; remoteproc is allocating the rings using
the DMA API.
> Yes wmb() is required to ensure ordering for MMIO.
> But here both accesses: index and ring - are for
> memory, not MMIO.
I'm doing IO with a device over shared memory. It does require
mandatory barriers as I explained.
> Is this something you see in practice?
Yes. These bugs are very real.
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