Re: [PATCH v7 05/10] x86/tdx: Handle port I/O

Sathyanarayanan Kuppuswamy
2021-10-18T18:42:12Z

On 10/18/21 6:52 AM, Tom Lendacky wrote:
> On 10/17/21 3:35 PM, Sathyanarayanan Kuppuswamy wrote:
>>
>> On 10/17/21 12:58 PM, Thomas Gleixner wrote:
>>> On Tue, Oct 05 2021 at 13:41, Kuppuswamy Sathyanarayanan wrote:
>>>> \
>>>>   static inline void outs##bwl(int port, const void *addr, unsigned
>>>> long count) \
>>>>   {                                    \
>>>> -    if (sev_key_active()) {                        \
>>>> +    if (sev_key_active() ||                        \
>>>> +        cc_platform_has(CC_ATTR_GUEST_UNROLL_STRING_IO)) {        \
>>> Instead of adding an extra check, can you please replace that
>>> sev_key_active() with cc_platform_has() completely?
>>
>> Yes. sev_key_active() can be removed and replaced with
>> cc_platform_has().
>>
>> Thomas Lendacky also proposed to introduce as common
>> static key which can be set by both AMD SEV and TDX code.
>>
>> @Thomas Lendacky, any comments?
>
> Either way works for me.
>
> For the cc_platform_has() path, you will need to update the
> amd_cc_platform_has() to return true for
> CC_ATTR_GUEST_UNROLL_STRING_IO for SEV only, i.e.:
>
>     case CC_ATTR_GUEST_UNROLL_STRING_IO:
>         return (sev_status & MSR_AMD64_SEV_ENABLED) &&
>                !(sev_status & MSR_AMD64_SEV_ES_ENABLED);

I will submit a separate cleanup patch to make SEV code use
CC_ATTR_GUEST_UNROLL_STRING_IO
first. That way, in this patch I can just set
CC_ATTR_GUEST_UNROLL_STRING_IO.

>
> Thanks,
> Tom

--
Sathyanarayanan Kuppuswamy
Linux Kernel Developer