linux-kernel - Re: [PATCH v5 5/9] iommufd: Add iommufd fault object

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Date: Mon, 20 May 2024 09:33:41 +0800
From: Baolu Lu <baolu.lu@...ux.intel.com>
To: "Tian, Kevin" <kevin.tian@...el.com>, Jason Gunthorpe <jgg@...pe.ca>,
 Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
 Robin Murphy <robin.murphy@....com>,
 Jean-Philippe Brucker <jean-philippe@...aro.org>,
 Nicolin Chen <nicolinc@...dia.com>, "Liu, Yi L" <yi.l.liu@...el.com>,
 Jacob Pan <jacob.jun.pan@...ux.intel.com>,
 Joel Granados <j.granados@...sung.com>
Cc: baolu.lu@...ux.intel.com, "iommu@...ts.linux.dev"
 <iommu@...ts.linux.dev>,
 "virtualization@...ts.linux-foundation.org"
 <virtualization@...ts.linux-foundation.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 5/9] iommufd: Add iommufd fault object

On 5/15/24 4:37 PM, Tian, Kevin wrote:
>> +
>> +		iopf_group_response(group, response.code);
> PCIe spec states that a response failure disables the PRI interface. For SR-IOV
> it'd be dangerous allowing user to trigger such code to VF to close the entire
> shared PRI interface.
> 
> Just another example lacking of coordination for shared capabilities between
> PF/VF. But exposing such gap to userspace makes it worse.

Yes. You are right.

> 
> I guess we don't want to make this work depending on that cleanup. The
> minimal correct thing is to disallow attaching VF to a fault-capable hwpt
> with a note here that once we turn on support for VF the response failure
> code should not be forwarded to the hardware. Instead it's an indication
> that the user cannot serve more requests and such situation waits for
> a vPRI reset to recover.

Is it the same thing to disallow PRI for VF in IOMMUFD?

Best regards,
baolu