Received-SPF: pass (google.com: domain of linux-kernel+bounces-116506-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:40f1:3f00::1 as permitted sender) client-ip=2604:1380:40f1:3f00::1;
Message-ID: <2ddd01fb-ec7d-4a7e-984b-31da78211f91@linux.intel.com>
Date: Mon, 25 Mar 2024 11:57:15 +0800
Precedence: bulk
MIME-Version: 1.0
User-Agent: Mozilla Thunderbird
Cc: baolu.lu@linux.intel.com, Kevin Tian <kevin.tian@intel.com>,
 Joerg Roedel <joro@8bytes.org>, Will Deacon <will@kernel.org>,
 Robin Murphy <robin.murphy@arm.com>,
 Jean-Philippe Brucker <jean-philippe@linaro.org>,
 Nicolin Chen <nicolinc@nvidia.com>, Yi Liu <yi.l.liu@intel.com>,
 Jacob Pan <jacob.jun.pan@linux.intel.com>,
 Joel Granados <j.granados@samsung.com>, iommu@lists.linux.dev,
 virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 3/8] iommufd: Add fault and response message
 definitions
Content-Language: en-US
To: Jason Gunthorpe <jgg@ziepe.ca>
References: <20240122073903.24406-1-baolu.lu@linux.intel.com>
 <20240122073903.24406-4-baolu.lu@linux.intel.com>
 <20240308175007.GW9225@ziepe.ca>
 <43ef5e3f-8a8e-4765-8025-b8207fd05f91@linux.intel.com>
 <20240322170410.GH66976@ziepe.ca>
From: Baolu Lu <baolu.lu@linux.intel.com>
In-Reply-To: <20240322170410.GH66976@ziepe.ca>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit

On 3/23/24 1:04 AM, Jason Gunthorpe wrote:
>>>> +struct iommu_hwpt_pgfault {
>>>> +	__u32 size;
>>>> +	__u32 flags;
>>>> +	__u32 dev_id;
>>>> +	__u32 pasid;
>>>> +	__u32 grpid;
>>>> +	__u32 perm;
>>>> +	__u64 addr;
>>>> +};
>>> Do we need an addr + size here? I've seen a few things where I wonder
>>> if that might become an enhancment someday.
>> I am not sure. The page size is not part of ATS/PRI. Can you please
>> elaborate a bit about how the size could be used? Perhaps I
>> misunderstood here?
> size would be an advice how much data the requestor is expecting to
> fetch. Eg of the PRI initiator knows it is going to do a 10MB transfer
> it could fill in 10MB and the OS could pre-fault in 10MB of IOVA.
> 
> It is not in the spec, it may never be in the spec, but it seems like
> it would be good to consider it, at least make sure we have
> compatability to add it later.

Thanks for the explanation. It sounds reasonable. I will take it and add
some comments to explain the motivation as you described above.

Best regards,
baolu