Re: [PATCH v7 net] octeontx2-af: switch qmem from coherent DMA alloc to streaming DMA mapping

[Ratheesh Kannoth]

On 2026-09-07 at 17:02:44, Leon Romanovsky (leon@xxxxxxxxxx) wrote:
> > > > +	 */
> > > > +	if (order > MAX_PAGE_ORDER) {
> > >
> > > Size is coming from the kernel, how can it be with order more than MAX_PAGE_ORDER?
> > There is contigious memory allocation request from driver for PF-to-VF mail box memory.
> > It is crossing max page order in newer platforms as number of VFs per PF increased.
>
> I'm not sure what this means. You can't create a VF without assigning it
> enough memory for DMA. You shouldn't get an "order > MAX_PAGE_ORDER"
> error at this stage. If you do, there is likely another bug involved.

I will move the MAX_PAGE_ORDER / size validation out of the DMA helper and handle any
allocation failure with a clear error at the call site, where we know the required size and VF count.

One question on dev_is_dma_coherent(): this qmem path relies on the platform being DMA-coherent
(as noted in the commit message). Would you prefer that we keep this check in this function as explicit
guard so that a future port to a non-I/O-coherent SoC fails early rather than silently misbehaving?