[Xen-devel] [PATCH v3 07/62] arm/acpi: Add arch_acpi_os_map_memory helper function for ARM

Jan Beulich JBeulich at suse.com
Mon Dec 7 02:32:40 PST 2015

>>> On 07.12.15 at 09:58, <zhaoshenglong at huawei.com> wrote:
> On 2015/11/30 22:47, Julien Grall wrote:
>> On 23/11/15 11:37, Stefano Stabellini wrote:
>>> > On Tue, 17 Nov 2015, shannon.zhao at linaro.org wrote:
>>>> >> From: Shannon Zhao <shannon.zhao at linaro.org>
>>> > could you please add a couple of lines to the commit message mentioning
>>> > why __va(phys) is an acceptable implementation of arch_acpi_os_map_memory?
>> FWIW, I already asked this question multiple time on the previous series
>> without clear answer.
>> __va should only be used when the memory is direct-mapped to Xen (i.e
>> accessible directly). On ARM64, this is only the case for the RAM. Can
>> someone confirm the ACPI will always reside to the RAM?
> I checked this with the UEFI SPEC. It says in 2.3.6 AArch64 Platforms:
> "If ACPI is supported :
> ● ACPI Tables loaded at boot time can be contained in memory of type
> EfiACPIReclaimMemory (recommended) or EfiACPIMemoryNVS."
> So I think it means the ACPI tables will always reside in RAM.

I think NVS doesn't necessarily mean RAM.


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