Re: [PATCH] scsi: pm8001: Fix phys_to_virt() usage on dma_addr_t

Niklas Cassel
2021-12-06T13:24:26Z

On Mon, Dec 06, 2021 at 09:42:23AM +0000, John Garry wrote:
> On 29/11/2021 10:46, Ajish.Koshy@microchip.com wrote:
> > Thanks John for the update. Based on the given issue,
> > we never tested on arm server.
> >
> > Further arm testing will depend on the availability of
> > the server.
> >
> > Meanwhile will do further test on x86 and update
> > on the observations.
>
> Have you tested on x86 with the IOMMU enabled? From my limited experience,
> out of the box the IOMMU is disabled in the BIOS on x86 machines - that is a
> very general statement. But this is not just an issue specific to arm64.

My limited experience tells me the opposite, that modern x64 servers
have IOMMU enabled by default:

E.g.:
https://www.dell.com/support/manuals/en-uk/poweredge-r7515/r7515_bios_pub/processor-settings?guid=guid-ec36d324-4f45-4bc1-bb51-de2db7cc5cd9&lang=en-us
https://support.hpe.com/hpesc/public/docDisplay?docId=a00025662en_us&docLocale=en_US

This driver not working properly on a system with an IOMMU just tells
us that the number of mainline users of this driver is very low :/

Kind regards,
Niklas