[PATCH 3/5] nvme: add support for copy offload

[Caleb Sander Mateos]

On Wed, May 21, 2025 at 9:30 PM Keith Busch <kbusch at kernel.org> wrote:
>
> On Wed, May 21, 2025 at 08:41:40PM -0700, Caleb Sander Mateos wrote:
> > For the record, that change broke Linux hosts sending DSM commands to
> > our NVMe controller, which was validating that the SGL length exactly
> > matches the number of data bytes implied by the command. I'm sure
> > we're in the minority of NVMe controller vendors in aggressively
> > validating the NVMe command parameters, but it was unfortunate to
> > discover this change in Linux's behavior.
>
> This is a fabrics target you're talking about? I assume so because pci
> would use PRP for a 4k payload, which doesn't encode transfer lengths.
> All the offending controllers were pci, so maybe we could have
> constrained the DSM over-allocation to that transport if we knew this
> was causing problems for fabrics.

Yes, fabrics. I would be fine with always mapping the full 4K data
length for PCI but using the exact length of the ranges for fabrics.

Best,
Caleb