On 2021-12-15 11:49:34 -0600, Michael Roth wrote: > > I think in the greater context of consolidating all the SME/SEV setup > and re-using code, this helper stands a high chance of eventually becoming > something more along the lines of sme_sev_parse_cpuid(), since otherwise > we'd end up re-introducing multiple helpers to parse the same 0x8000001F > fields if we ever need to process any of the other fields advertised in > there. Given that, it makes sense to reserve the return value as an > indication that either SEV or SME are enabled, and then have a > pass-by-pointer parameters list to collect the individual feature > bits/encryption mask for cases where SEV/SME are enabled, which are only > treated as valid if sme_sev_parse_cpuid() returns 0. > > So Venu's original approach of passing the encryption mask by pointer > seems a little closer toward that end, but I also agree Tom's approach > is cleaner for the current code base, so I'm fine either way, just > figured I'd mention this. > > I think needing to pass in the SME/SEV CPUID bits to tell the helper when > to parse encryption bit and when not to is a little bit awkward though. > If there's some agreement that this will ultimately serve the purpose of > handling all (or most) of SME/SEV-related CPUID parsing, then the caller > shouldn't really need to be aware of any individual bit positions. > Maybe a bool could handle that instead, e.g.: > > int get_me_bit(bool sev_only, ...) > > or > > int sme_sev_parse_cpuid(bool sev_only, ...) > > where for boot/compressed sev_only=true, for kernel proper sev_only=false. I can implement it this way too. But I am wondering if having a boolean argument limits us from handling any future additions to the bit positions. Boris & Tom, which implementation would you prefer? Venu
