linux-kernel - RE: [PATCH v8 3/3] iommu/arm-smmu: Add global/context fault implementation hooks

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Message-ID: <BYAPR12MB2822911461ABAAC205E76DE7B36C0@BYAPR12MB2822.namprd12.prod.outlook.com>
Date:   Wed, 1 Jul 2020 19:22:46 +0000
From:   Krishna Reddy <vdumpa@...dia.com>
To:     Robin Murphy <robin.murphy@....com>,
        Jonathan Hunter <jonathanh@...dia.com>
CC:     Sachin Nikam <Snikam@...dia.com>,
        "nicoleotsuka@...il.com" <nicoleotsuka@...il.com>,
        Mikko Perttunen <mperttunen@...dia.com>,
        "Bryan Huntsman" <bhuntsman@...dia.com>,
        "will@...nel.org" <will@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Pritesh Raithatha" <praithatha@...dia.com>,
        Timo Alho <talho@...dia.com>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        Nicolin Chen <nicolinc@...dia.com>,
        "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
        Yu-Huan Hsu <YHsu@...dia.com>,
        Thierry Reding <treding@...dia.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        Bitan Biswas <bbiswas@...dia.com>
Subject: RE: [PATCH v8 3/3] iommu/arm-smmu: Add global/context fault
 implementation hooks

>> With shared irq line, the context fault identification is not optimal already.  Reading all the context banks all the time can be additional mmio read overhead. But, it may not hurt the real use cases as these happen only when there are bugs.

>Right, I did ponder the idea of a whole programmatic "request_context_irq" hook that would allow registering the handler for both interrupts with the appropriate context bank and instance data, but since all interrupts are currently unexpected it seems somewhat hard to justify the extra complexity. Obviously we can revisit this in future if you want to start actually doing something with faults like the qcom GPU folks do.

Thanks, I would just avoid making changes to interrupt handlers till it is really necessary in future. The current code would just be simple and functional with more interrupts when there are multiple faults.

-KR