Re: [PATCH 2/2] block: sed-opal: Cache-line-align the cmd/resp buffers

From: Christoph Hellwig
Date: Sat Sep 10 2022 - 01:32:20 EST

On Fri, Sep 09, 2022 at 10:19:16PM +0300, Serge Semin wrote:
> In accordance with [1] the DMA-able memory buffers must be
> cacheline-aligned otherwise the cache writing-back and invalidation
> performed during the mapping may cause the adjacent data being lost. It's
> specifically required for the DMA-noncoherent platforms. Seeing the
> opal_dev.{cmd,resp} buffers are used for DMAs in the NVME and SCSI/SD
> drivers in framework of the nvme_sec_submit() and sd_sec_submit() methods
> respectively we must make sure the passed buffers are cacheline-aligned to
> prevent the denoted problem.

Same comment as for the previous one, this should work, but I think
separate allocations for the DMAable buffers would document the intent
much better. Given that the opal initialization isn't a fast path
I don't think that the overhead should matter either.