Re: [PATCH v5 16/16] x86/tdx: Add cmdline option to force use of ioremap_host_shared

Andi Kleen
2021-10-15T05:51:07Z

> I thought you basically create an OperationRegion of SystemMemory type,
> and off you go. Maybe the OSPM in Linux is clever and protects
> some memory, I wouldn't know.

I investigated this now, and it looks like acpi is using
ioremap_cache(). We can hook into that and force non sharing. It's
probably safe to assume that this is not used on real IO devices.

I think there are still some other BIOS mappings that use just plain
ioremap() though.

-Andi