linux-kernel - Re: [PATCH V2 2/3] vfio, platform: make reset driver a requirement

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Message-ID: <56E5A271.6000408@codeaurora.org>
Date:	Sun, 13 Mar 2016 13:25:05 -0400
From:	Sinan Kaya <okaya@...eaurora.org>
To:	kvm@...r.kernel.org, timur@...eaurora.org, cov@...eaurora.org,
	jcm@...hat.com, eric.auger@...aro.org
Cc:	shankerd@...eaurora.org, vikrams@...eaurora.org,
	marc.zyngier@....com, mark.rutland@....com,
	devicetree@...r.kernel.org, vinod.koul@...el.com,
	agross@...eaurora.org, linux-arm-msm@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	Baptiste Reynal <b.reynal@...tualopensystems.com>,
	Alex Williamson <alex.williamson@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2 2/3] vfio, platform: make reset driver a requirement

On 3/11/2016 11:54 AM, Sinan Kaya wrote:
> The code was allowing platform devices to be used without a supporting VFIO
> reset driver. The hardware can be left in some inconsistent state after a
> guest machine abort.
> 
> The reset driver will put the hardware back to safe state and disable
> interrupts before returning the control back to the host machine.
> 
> Signed-off-by: Sinan Kaya <okaya@...eaurora.org>
> ---
>  drivers/vfio/platform/vfio_platform_common.c | 16 +++++++++-------
>  1 file changed, 9 insertions(+), 7 deletions(-)
> 
I was looking at the code. It looks like this is going to break VFIO AMBA. The
common implementation is shared with AMBA and platform devices.

I couldn't see a reset function for AMBA devices.

Is there anyway to write reset function for it? I have no experience with 
AMBA devices.

Would you include a reset needed flag and just not require it for AMBA? 
(I honestly don't like this idea)

-- 
Sinan Kaya
Qualcomm Technologies, Inc. on behalf of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project