Re: [PATCH 2/2] acpi, apei: use appropriate pgprot_t to map GHES memory

[Ingo Molnar <mingo@kernel.org>]

* Jonathan (Zhixiong) Zhang <zjzhang@codeaurora.org> wrote:

> From: "Jonathan (Zhixiong) Zhang" <zjzhang@codeaurora.org>
> 
> With ACPI APEI firmware first handling, generic hardware error
> record is updated by firmware in GHES memory region. On an arm64
> platform, firmware updates GHES memory region with uncached
> access attribute, and then Linux reads stale data from cache.

This paragraph *still* doesn't parse for me. It's not any English
I can recognize: what is a 'With ACPI APEI firmware first handling'?

> With current code, GHES memory region is mapped with PAGE_KERNEL
> based on the assumption that cache coherency of GHES memory region
> is maintained by firmware on all platforms. This assumption is
> not true for above mentioned arm64 platform.
> 
> Instead GHES memory region should be mapped with page protection type
> according to what is returned from arch_apei_get_mem_attribute().

... plus what this changelog still doesn't mention is the most important part of 
any bug fix description: how does the user notice this in practice and why does he 
care?

Thanks,

	Ingo