On 06/03/2016 05:16 PM, Mihai Claudiu Caraman wrote:
-----Original Message-----
From: Peter Maydell [mailto:peter.mayd...@linaro.org]
Sent: Friday, June 03, 2016 5:38 PM
To: Mihai Claudiu Caraman <mike.cara...@nxp.com>
Cc: Bogdan Purcareata <bogdan.purcare...@nxp.com>; QEMU Developers <qemu-devel@nongnu.org>; Peter
Crosthwaite <crosthwaite.pe...@gmail.com>; Alexander Graf <ag...@suse.de>; qemu-arm
<qemu-...@nongnu.org>; Eric Auger <eric.au...@linaro.org>
Subject: Re: [Qemu-devel] [PATCH 2/2] arm/virt: Mark pcie controller node as
dma-coherent
On 3 June 2016 at 15:22, Mihai Claudiu Caraman <mike.cara...@nxp.com> wrote:
In particular for virtual and emulated devices the host CPU behaves as
a DMA coherent 'device'. This should have been stated in patch
description.
Wouldn't that imply that we should just always have the "dma-coherent"
property set, and we don't need to do any of the messing around looking at the
host sysfs ?
thanks
-- PMM
We can always set "dma-coherent" for virtual and emulated devices but not for passthrough
devices. So we can't have one PCIe controller for all devices marked as "dma-coherent".
The original patch is about the case where PCI is already cache coherent
on the host.
I think at the end of the day this is simply outside of QEMU's scope to
decide. What we can do is set dma-coherent per default (if Will and Ard
agree) on the default PCIe bus and add code that allows to spawn a
secondary PCIe bus which can then have different dma-coherent attributes
and that you can then plug your non-coherent vfio devices into.
Alex
