Re: [asahilinux:nvme/dev 13/17] drivers/nvme/host/pci.c:2249:2-3: Unneeded semicolon

[Sven Peter]

On Mon, Aug 9, 2021, at 17:53, Arnd Bergmann wrote:
> On Mon, Aug 9, 2021 at 4:29 PM Christoph Hellwig <hch at infradead.org> wrote:
> > Also can one of you look how PRPs are actually used by MacOS?  Given
> > that this device always seems to be behind a IOMMU creating one entry
> > per page seems rather weird given that the apple_nvmmu_tcb structure
> > already contains the full length.  Maybe it actually ignores all but
> > the first PRP?
> 
> I'll leave this up to Sven to answer. He also wrote the iommu driver,
> so he probably has a good idea of what is going on here already.
> 
>       Arnd
> 

Not yet, but figuring out how this NVMe-IOMMU works in detail was
already on my TODO list :-)

Some background - the M1 has at least four different IOMMU-like
HW blocks:
DART (for which I wrote a driver and where I'd actually know what's going
on in detail), SART (simple DMA address filter required by the NVMe
co-processor for non-nvme transactions), this weird NVMe IOMMU (that
also seems to be somehow related to disk encryption) and GART for their GPU.



Sven