linux-kernel - Re: [PATCH v9 06/19] vfio/platform: return info for bound device

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Message-ID: <546DFA04.9060901@linaro.org>
Date:	Thu, 20 Nov 2014 15:26:12 +0100
From:	Eric Auger <eric.auger@...aro.org>
To:	Antonios Motakis <a.motakis@...tualopensystems.com>,
	Alex Williamson <alex.williamson@...hat.com>
CC:	kvm-arm <kvmarm@...ts.cs.columbia.edu>,
	Linux IOMMU <iommu@...ts.linux-foundation.org>,
	Will Deacon <will.deacon@....com>,
	VirtualOpenSystems Technical Team <tech@...tualopensystems.com>,
	Christoffer Dall <christoffer.dall@...aro.org>,
	Kim Phillips <kim.phillips@...escale.com>,
	Marc Zyngier <marc.zyngier@....com>,
	VFIO DRIVER <kvm@...r.kernel.org>,
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v9 06/19] vfio/platform: return info for bound device

On 11/20/2014 03:10 PM, Antonios Motakis wrote:
> On Wed, Nov 12, 2014 at 5:36 PM, Alex Williamson
> <alex.williamson@...hat.com> wrote:
>> On Wed, 2014-11-12 at 11:32 +0100, Eric Auger wrote:
>>> On 10/27/2014 07:07 PM, Antonios Motakis wrote:
>>>> A VFIO userspace driver will start by opening the VFIO device
>>>> that corresponds to an IOMMU group, and will use the ioctl interface
>>>> to get the basic device info, such as number of memory regions and
>>>> interrupts, and their properties. This patch enables the
>>>> VFIO_DEVICE_GET_INFO ioctl call.
>>>>
>>>> Signed-off-by: Antonios Motakis <a.motakis@...tualopensystems.com>
>>>> ---
>>>>  drivers/vfio/platform/vfio_platform_common.c | 23 ++++++++++++++++++++---
>>>>  1 file changed, 20 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/drivers/vfio/platform/vfio_platform_common.c b/drivers/vfio/platform/vfio_platform_common.c
>>>> index e0fdbc8..cb20526 100644
>>>> --- a/drivers/vfio/platform/vfio_platform_common.c
>>>> +++ b/drivers/vfio/platform/vfio_platform_common.c
>>>> @@ -43,10 +43,27 @@ static int vfio_platform_open(void *device_data)
>>>>  static long vfio_platform_ioctl(void *device_data,
>>>>                        unsigned int cmd, unsigned long arg)
>>>>  {
>>>> -   if (cmd == VFIO_DEVICE_GET_INFO)
>>>> -           return -EINVAL;
>>>> +   struct vfio_platform_device *vdev = device_data;
>>>> +   unsigned long minsz;
>>>> +
>>>> +   if (cmd == VFIO_DEVICE_GET_INFO) {
>>>> +           struct vfio_device_info info;
>>>> +
>>>> +           minsz = offsetofend(struct vfio_device_info, num_irqs);
>>>> +
>>>> +           if (copy_from_user(&info, (void __user *)arg, minsz))
>>>> +                   return -EFAULT;
>>>> +
>>>> +           if (info.argsz < minsz)
>>>> +                   return -EINVAL;
>>>> +
>>>> +           info.flags = vdev->flags;
>>>> +           info.num_regions = 0;
>>>> +           info.num_irqs = 0;
>>> Seems a bit weird to me to enable the modality but returning zeroed
>>> values. Shouldn't we put that patch after VFIO_DEVICE_GET_REGION_INFO
>>> and VFIO_DEVICE_GET_IRQ_INFO ones?
>>
>> I actually like how Antonios has started from a base framework, exposing
>> a device but none of the resources and then incrementally adds each
>> component.  It's also a good showcase of the VFIO ABI that we can do
>> things like this.  Thanks,
> 
> I also agree with Alex with this. But of course I'm not married with
> any particular splitting style, in case we decide to change this.

Hi Antonios,
please keep as is. I also learn each day about splitting style ;-)
Best Regards
Eric
> 
>>
>> Alex
>>

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