[edk2-devel] [PATCH RFC v2 05/28] MdePkg: Add AsmPvalidate() support

[Brijesh Singh]

On 5/4/21 2:07 PM, Brijesh Singh via groups.io wrote:
>> Return EFI_UNSUPPORTED (0x8000_0003), or even EFI_NO_MAPPING
>> (0x8000_0017), for value 6 (FAIL_SIZEMISMATCH).
> I am not sure if we really want to do this. You will see later in the
> patches that in some cases the PVALIDATE will return a failure and we
> will need to know the failure code to determine the next steps.
> Especially this particular error code is used later. This error happens
> when the page size of the backing pages does not match with the
> pvalidated size. In those cases we need to retry the PVALIDATE with
> lower page size so that a validation succeed. One such a example is:
>
> - Guest ask hypervisor to add the page as 2M in RMP table.
>
> - Hypervisor added the page as 512 4K pages - because it was not able to
> find a large backing pages.
>
> - Guest attempts to pvalidate the page as a 2M. The pvalidate will
> return a failure saying its a size mismatch between the requested
> pvalidated and RMP table. The recommendation is that guest should try
> with a smaller page size.
>
> I would prefer to pass the pvalidate error as-is to caller so that it
> can make the correct decision.
>
I am perfectly fine if the function return UINTN and then use #define
instead of the enum to define the PVALIDATE return code. So that caller
can check the error code. Let me know your thought on #define instead of
the enum.

-Brijesh



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