Re: [RFC PATCH V1 11/12] libxl: Insert "dma-coherent" property into virtio-mmio device node

[Oleksandr <olekstysh@xxxxxxxxx>]

On 05.08.20 02:23, Stefano Stabellini wrote:

Hi Stefano

> On Mon, 3 Aug 2020, Oleksandr Tyshchenko wrote:
> > From: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
> >
> > Without "dma-coherent" property present in virtio-mmio device node,
> > guest assumes it is non-coherent and making non-cacheable accesses
> > to the vring when the DMA API is used for vring operations.
> > But virtio-mmio device which runs at the host size is making cacheable
> > accesses to vring. This all may result in a loss of coherency between
> > the guest and host.
> >
> > With this patch we can avoid modifying guest at all, otherwise we
> > need to force VirtIO framework to not use DMA API for vring operations.
> >
> > Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
> This should also be folded in the first patch for libxl
Agree, will do



--
Regards,

Oleksandr Tyshchenko