Re: [PATCH v5 04/12] x86/tdx: Add protected guest support for TDX guest

Kuppuswamy, Sathyanarayanan
2021-08-04T22:26:19Z

On 8/4/21 3:03 PM, Dave Hansen wrote:
>>> +#include <asm/processor.h>
>>> +#include <asm/tdx.h>
>>> +
>>> #ifndef __ASSEMBLY__
>>>
>>> static inline bool prot_guest_has(unsigned int attr)
>>> {
>>> if (sme_me_mask)
>>> return amd_prot_guest_has(attr);
>>> + else if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL)
>> Why not "boot_cpu_has(X86_FEATURE_TDX_GUEST)"?
> Even better: cpu_feature_enabled(X86_FEATURE_TDX_GUEST). That gets you
> both static patching*and* compile-time optimization if you hook
> X86_FEATURE_TDX_GUEST into disabled-features.h.

This is how Borislav preferred it. tdx_prot_guest_has() internally uses
cpu_feature_enabled(X86_FEATURE_TDX_GUEST) to return the status.

I think the intention is to keep the first call generic (non TDX
specific). So that it can be extended for other use cases.

--
Sathyanarayanan Kuppuswamy
Linux Kernel Developer