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Message-ID: <155838f4-eac0-4e8c-adc6-e4efa2a786e2@linux.intel.com>
Date: Thu, 13 Jul 2023 12:02:09 +0800
From: Baolu Lu <baolu.lu@...ux.intel.com>
To: Jean-Philippe Brucker <jean-philippe@...aro.org>
Cc: baolu.lu@...ux.intel.com, "Tian, Kevin" <kevin.tian@...el.com>,
Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
Robin Murphy <robin.murphy@....com>,
Jason Gunthorpe <jgg@...pe.ca>,
Nicolin Chen <nicolinc@...dia.com>,
"Liu, Yi L" <yi.l.liu@...el.com>,
Jacob Pan <jacob.jun.pan@...ux.intel.com>,
"iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/9] iommu: Add common code to handle IO page faults
On 2023/7/12 17:45, Jean-Philippe Brucker wrote:
> On Wed, Jul 12, 2023 at 10:32:13AM +0800, Baolu Lu wrote:
>>> btw is there value of moving the group handling logic from
>>> iommu_queue_iopf() to this common function?
>>>
>>> I wonder whether there is any correctness issue if not forwarding
>>> partial request to iommufd. If not this can also help reduce
>>> notifications to the user until the group is ready.
>>
>> I don't think there's any correctness issue. But it should be better if
>> we can inject the page faults to vm guests as soon as possible. There's
>> no requirement to put page requests to vIOMMU's hardware page request
>> queue at the granularity of a fault group. Thoughts?
>
> Not sure I understand you correctly, but we can't inject partial fault
> groups: if the HW PRI queue overflows, the last fault in a group may be
> lost, so the non-last faults in that group already injected won't be
> completed (until PRGI reuse), leaking PRI request credits and guest
> resources.
Yeah, that's how vIOMMU injects the faults. On host/hypervisor side, my
understanding is that faults should be uploaded as soon as possible.
Best regards,
baolu
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