Re: [Xen-devel] [PATCH] efi/libstub/fdt: Standardize the names of EFI stub parameters

[Jan Beulich]

>>> On 14.09.15 at 11:36, <ard.biesheuvel@xxxxxxxxxx> wrote:
> On 14 September 2015 at 11:31, Shannon Zhao <zhaoshenglong@xxxxxxxxxx> wrote:
>> My understanding is that if there are no EFI_MEMORY_RUNTIME regions, it
>> means we can't use runtime services and should not set the bit
>> EFI_RUNTIME_SERVICES of efi.flags. But if efi_virtmap_init() return
>> true, the bit will be set.
>>
> 
> As I said, if you don't want the EFI_RUNTIME_SERVICES bit to be set
> for other reasons, don't rig efi_virtmap_init() to return false when
> it shouldn't.
> 
>>> The absence of such regions is allowed by the spec, so
>>> efi_virtmap_init() is correct imo to return success.
>>>
>> Sorry, not well know about the spec. Could you point out where the spec
>> says this?
>>
> 
> Well, I think it doesn't work that way. You are claiming that a memory
> map without at least one EFI_MEMORY_RUNTIME constitutes an error
> condition, so the burden is on you to provide a reference to the spec
> that says you must have at least one such region.

Sure, from a spec pov you're right. But where would runtime
services code/data live when there's not a single region marked
as needing a runtime mapping. IOW while the spec doesn't say
so, assuming no runtime services when there's not at least one
executable region with the runtime flag set could serve as a stop
gap measure against flawed firmware.

Jan

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