linux-kernel - Re: [PATCH v6 05/10] iommufd: Add fault and response message definitions

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Date: Thu, 13 Jun 2024 12:54:16 +0800
From: Baolu Lu <baolu.lu@...ux.intel.com>
To: Jason Gunthorpe <jgg@...pe.ca>, "Tian, Kevin" <kevin.tian@...el.com>
Cc: baolu.lu@...ux.intel.com, 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>,
 "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 v6 05/10] iommufd: Add fault and response message
 definitions

On 6/12/24 9:19 PM, Jason Gunthorpe wrote:
> On Fri, Jun 07, 2024 at 09:38:38AM +0000, Tian, Kevin wrote:
>>> From: Baolu Lu<baolu.lu@...ux.intel.com>
>>> Sent: Thursday, June 6, 2024 2:28 PM
>>>
>>> On 6/5/24 4:28 PM, Tian, Kevin wrote:
>>>>> From: Lu Baolu<baolu.lu@...ux.intel.com>
>>>>> Sent: Monday, May 27, 2024 12:05 PM
>>>>>
>>>>> +
>>>>> +/**
>>>>> + * struct iommu_hwpt_page_response - IOMMU page fault response
>>>>> + * @size: sizeof(struct iommu_hwpt_page_response)
>>>>> + * @flags: Must be set to 0
>>>>> + * @dev_id: device ID of target device for the response
>>>>> + * @pasid: Process Address Space ID
>>>>> + * @grpid: Page Request Group Index
>>>>> + * @code: One of response code in enum
>>> iommufd_page_response_code.
>>>>> + * @cookie: The kernel-managed cookie reported in the fault message.
>>>>> + */
>>>>> +struct iommu_hwpt_page_response {
>>>>> +	__u32 size;
>>>>> +	__u32 flags;
>>>>> +	__u32 dev_id;
>>>>> +	__u32 pasid;
>>>>> +	__u32 grpid;
>>>>> +	__u32 code;
>>>>> +	__u32 cookie;
>>>>> +	__u32 reserved;
>>>>> +};
>>>> with the response queue per fault object we don't need all fields here,
>>>> e.g. dev_id, pasid, etc. Cookie is sufficient.
> Wait, why did we make it per object? The fault FD is supposed to be
> sharable across HWPTs.

The fault FD is shareable across HWPTs. Kevin was suggesting that the
response queue (for all outstanding IOPFs awaiting responses) could be
put in the fault structure.

Best regards,
baolu