linux-kernel - Re: [PATCH v4 09/13] iommu/arm-smmu-v3: Implement set_dev

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Date:   Mon, 26 Jun 2023 11:14:38 -0700
From:   Nicolin Chen <nicolinc@...dia.com>
To:     Michael Shavit <mshavit@...gle.com>
CC:     Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
        "Joerg Roedel" <joro@...tes.org>, <jean-philippe@...aro.org>,
        <jgg@...dia.com>, <baolu.lu@...ux.intel.com>,
        <linux-arm-kernel@...ts.infradead.org>, <iommu@...ts.linux.dev>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 09/13] iommu/arm-smmu-v3: Implement set_dev_pasid

On Mon, Jun 26, 2023 at 10:33:58AM +0800, Michael Shavit wrote:
 
> > Would you please elaborate a bit more for the use case of
> allowing that?
> 
> In short; to support devices that use SSID to isolate different
> (device) contexts. Those contexts (and the memory available to them)
> is partially managed by the device's Kernel driver.

What can be a real world use case for that?

> > And which test configuration do you cover
> using smmute? Would you mind sharing your test commands?
> 
> I used the setup suggested by Jean in
> https://lore.kernel.org/all/20230511195928.GA288490@myrica/ , with the
> following commands:
> >>>
> # Basic test
> ./smmute;
> ./smmute -u mmap;
> 
> # Test invalid access to not-mapped address
> ./smmute -u mmap -f drv;
> 
> # Test invalid access after unmap
> ./smmute -u mmap -f write -d;
> 
> # Check smmu_mn released when killed
> mount -t tracefs nodev /sys/kernel/tracing;
> echo 1 > /sys/kernel/tracing/events/iommu/enable;
> echo 1 > /sys/kernel/tracing/events/smmu/enable;
> ./smmute -u mmap -k bind;
> cat /sys/kernel/tracing/trace;
> <<<

OK. Thanks for sharing.

> This only covers existing SVA functionality. To test the functionality
> introduced by this patch, I used a device capable of generating DMA
> transactions w/ SSID and a test driver with following tests:
> 1. Successful dma Read/Write to buffer mapped on domain attached with pasid
> 2. Unsuccessful dma Read/Write to same buffer after domain detached
> from pasid, or after buffer unmapped from domain
> 3. Variations of the above with a domain attached to multiple pasids
> 
> I've been considering migrating those tests to the smmute driver if
> that would be valuable.

Is this on Gerrit too?

Thanks
Nicolin