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


On 2015/11/30 22:47, Julien Grall wrote:
> Hi,
> On 23/11/15 11:37, Stefano Stabellini wrote:
>> > On Tue, 17 Nov 2015, shannon.zhao@xxxxxxxxxx wrote:
>>> >> From: Shannon Zhao <shannon.zhao@xxxxxxxxxx>
>> > 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.


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