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

[Shannon Zhao <zhaoshenglong@huawei.com>]

On 2015/9/14 17:09, Ard Biesheuvel wrote:
> On 14 September 2015 at 10:42, Shannon Zhao <zhaoshenglong@huawei.com> wrote:
> [..]
> 
>>
>> It only needs to apply following patch to fix a bug in Linux kernel when
>> mapping EFI_MEMORY_RUNTIME memory.
>>
> 
> Could you explain why you think efi_virtmap_init() should fail if
> there are no EFI_MEMORY_RUNTIME regions?
> 

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.

> 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?

> If you are trying to work around the issue where Xen does not expose
> any Runtime Services regions, there is simply no way to do that and be
> still UEFI compliant. I have suggested before that we should perhaps
> tolerate this anyway, by considering the case where the EFI System
> Table has a NULL runtime services pointer. But rigging
> efi_virtmap_init() like this is really not the way to achieve that.
> 

-- 
Shannon