linux-kernel - Re: [PATCH v9 04/11] iommu: Add sva iommu

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Message-ID: <eebe4e1b-f94c-53aa-0259-c0229c615830@linux.intel.com>
Date:   Wed, 29 Jun 2022 12:44:51 +0800
From:   Baolu Lu <baolu.lu@...ux.intel.com>
To:     "Tian, Kevin" <kevin.tian@...el.com>,
        Joerg Roedel <joro@...tes.org>,
        Jason Gunthorpe <jgg@...dia.com>,
        Christoph Hellwig <hch@...radead.org>,
        "Raj, Ashok" <ashok.raj@...el.com>, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Jean-Philippe Brucker <jean-philippe@...aro.com>,
        "Jiang, Dave" <dave.jiang@...el.com>, Vinod Koul <vkoul@...nel.org>
Cc:     baolu.lu@...ux.intel.com, Eric Auger <eric.auger@...hat.com>,
        "Liu, Yi L" <yi.l.liu@...el.com>,
        "Pan, Jacob jun" <jacob.jun.pan@...el.com>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>
Subject: Re: [PATCH v9 04/11] iommu: Add sva iommu_domain support

On 2022/6/29 09:54, Tian, Kevin wrote:
>> From: Baolu Lu <baolu.lu@...ux.intel.com>
>> Sent: Tuesday, June 28, 2022 7:34 PM
>>
>> On 2022/6/28 16:50, Tian, Kevin wrote:
>>>> From: Baolu Lu<baolu.lu@...ux.intel.com>
>>>> Sent: Tuesday, June 28, 2022 1:41 PM
>>>>>>     struct iommu_domain {
>>>>>>     	unsigned type;
>>>>>>     	const struct iommu_domain_ops *ops;
>>>>>>     	unsigned long pgsize_bitmap;	/* Bitmap of page sizes in use */
>>>>>> -	iommu_fault_handler_t handler;
>>>>>> -	void *handler_token;
>>>>>>     	struct iommu_domain_geometry geometry;
>>>>>>     	struct iommu_dma_cookie *iova_cookie;
>>>>>> +	union {
>>>>>> +		struct {	/* IOMMU_DOMAIN_DMA */
>>>>>> +			iommu_fault_handler_t handler;
>>>>>> +			void *handler_token;
>>>>>> +		};
>>>>> why is it DMA domain specific? What about unmanaged
>>>>> domain? Unrecoverable fault can happen on any type
>>>>> including SVA. Hence I think above should be domain type
>>>>> agnostic.
>>>> The report_iommu_fault() should be replaced by the new
>>>> iommu_report_device_fault(). Jean has already started this work.
>>>>
>>>> https://lore.kernel.org/linux-iommu/Yo4Nw9QyllT1RZbd@myrica/
>>>>
>>>> Currently this is only for DMA domains, hence Robin suggested to make it
>>>> exclude with the SVA domain things.
>>>>
>>>> https://lore.kernel.org/linux-iommu/f3170016-4d7f-e78e-db48-
>>>> 68305f683349@....com/
>>> Then it's worthy a comment that those two fields are for
>>> some legacy fault reporting stuff and DMA type only.
>>
>> The iommu_fault and SVA fields are exclusive. The former is used for
>> unrecoverable DMA remapping faults, while the latter is only interested
>> in the recoverable page faults.
>>
>> I will update the commit message with above explanation. Does this work
>> for you?
>>
> 
> Not exactly. Your earlier explanation is about old vs. new API thus
> leaving the existing fault handler with current only user is fine.
> 
> but this is not related to unrecoverable vs. recoverable. As I said
> unrecoverable could happen on all domain types. Tying it to
> DMA-only doesn't make sense and I think in the end the new
> iommu_report_device_fault() will need support both. Is it not the
> case?

You are right.

The report_iommu_fault() should be replaced by the new
iommu_report_device_fault(). Leave the existing fault handler with the
existing users and the newly added SVA members should exclude it.

Best regards,
baolu