* min_align_mask Re: [PATCH V3 13/13] HV/Storvsc: Add Isolation VM support for storvsc driver
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@ 2021-08-24 8:49 ` hch
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From: hch @ 2021-08-24 8:49 UTC (permalink / raw)
To: Michael Kelley
Cc: hch@lst.de, Tianyu Lan, KY Srinivasan, Haiyang Zhang,
Stephen Hemminger, wei.liu@kernel.org, Dexuan Cui,
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mpi3mr-linuxdrv.pdl
On Fri, Aug 20, 2021 at 03:40:08PM +0000, Michael Kelley wrote:
> I see that the swiotlb code gets and uses the min_align_mask field. But
> the NVME driver is the only driver that ever sets it, so the value is zero
> in all other cases. Does swiotlb just use PAGE_SIZE in that that case? I
> couldn't tell from a quick glance at the swiotlb code.
The encoding isn't all that common. I only know it for the RDMA memory
registration format, and RDMA in general does not interact very well
with swiotlb (although the in-kernel drivers should work fine, it is
userspace RDMA that is the problem). It seems recently a new driver
using the format (mpi3mr) also showed up. All these should probably set
the min_align_mask.
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