linux-kernel - Re: [PATCH v7 9/9] vfio/type1: Handle different mdev isolation type

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Message-ID: <939783f6-95e5-1413-8a2a-0e17c71110ef@linux.intel.com>
Date:   Wed, 20 Mar 2019 13:52:52 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     Neo Jia <cjia@...dia.com>,
        Alex Williamson <alex.williamson@...hat.com>
Cc:     baolu.lu@...ux.intel.com, Joerg Roedel <joro@...tes.org>,
        David Woodhouse <dwmw2@...radead.org>,
        Kirti Wankhede <kwankhede@...dia.com>, ashok.raj@...el.com,
        sanjay.k.kumar@...el.com, jacob.jun.pan@...el.com,
        kevin.tian@...el.com,
        Jean-Philippe Brucker <jean-philippe.brucker@....com>,
        yi.l.liu@...el.com, yi.y.sun@...el.com, peterx@...hat.com,
        tiwei.bie@...el.com, xin.zeng@...el.com,
        iommu@...ts.linux-foundation.org, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>
Subject: Re: [PATCH v7 9/9] vfio/type1: Handle different mdev isolation type

Hi Neo,

On 3/9/19 2:03 AM, Neo Jia wrote:
> On Thu, Mar 07, 2019 at 04:56:23PM -0700, Alex Williamson wrote:
>> On Thu, 7 Mar 2019 00:44:54 -0800
>> Neo Jia <cjia@...dia.com> wrote:
>>
>>> On Fri, Feb 22, 2019 at 10:19:27AM +0800, Lu Baolu wrote:
>>>> This adds the support to determine the isolation type
>>>> of a mediated device group by checking whether it has
>>>> an iommu device. If an iommu device exists, an iommu
>>>> domain will be allocated and then attached to the iommu
>>>> device. Otherwise, keep the same behavior as it is.
>>>>
>>>> Cc: Ashok Raj <ashok.raj@...el.com>
>>>> Cc: Jacob Pan <jacob.jun.pan@...ux.intel.com>
>>>> Cc: Kevin Tian <kevin.tian@...el.com>
>>>> Signed-off-by: Sanjay Kumar <sanjay.k.kumar@...el.com>
>>>> Signed-off-by: Liu Yi L <yi.l.liu@...el.com>
>>>> Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
>>>> Reviewed-by: Jean-Philippe Brucker <jean-philippe.brucker@....com>
>>>> ---
>>>>   drivers/vfio/vfio_iommu_type1.c | 48 ++++++++++++++++++++++++++++-----
>>>>   1 file changed, 41 insertions(+), 7 deletions(-)
>>>>
>>>> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
>>>> index ccc4165474aa..f1392c582a3c 100644
>>>> --- a/drivers/vfio/vfio_iommu_type1.c
>>>> +++ b/drivers/vfio/vfio_iommu_type1.c
>>>> @@ -1368,13 +1368,40 @@ static void vfio_iommu_detach_group(struct vfio_domain *domain,
>>>>   		iommu_detach_group(domain->domain, group->iommu_group);
>>>>   }
>>>>     
>>>
>>> Hi Baolu,
>>>
>>> To allow IOMMU-awared mdev, I think you need to modify the
>>> vfio_iommu_type1_pin_pages and vfio_iommu_type1_unpin_pages to remove the
>>> iommu->external_domain check.
>>>
>>> Could you please include that in your patch? If not, I can send out a separate
>>> patch to address that issue.
>>
>> I figured it was intentional that an IOMMU backed mdev would not use
>> the pin/unpin interface and therefore the exiting -EINVAL returns would
>> be correct.  Can you elaborate on the use case for still requiring the
>> mdev pin/unpin interface for these devices?  Thanks,
> 
> Sure. We are using this api to fetch a pfn of a guest physical address so we can
> access it for PV.

Okay, I will remove these two checks in the next version.

Best regards,
Lu Baolu