Re: [PATCH v6 00/12] SVM cleanup and INVPCID feature support

Paolo Bonzini
2021-03-24T22:00:12Z

On 24/03/21 22:21, Borislav Petkov wrote:
> if (kaiser_enabled)
> invpcid_flush_one(X86_CR3_PCID_ASID_USER, addr);
> + else
> + asm volatile("invlpg (%0)" ::"r" (addr) : "memory");
> +
> invpcid_flush_one(X86_CR3_PCID_ASID_KERN, addr);
> }

I think the kernel ASID flush can also be moved under the "if"?

> and the reason why it does, IMHO, is because on AMD, kaiser_enabled is
> false because AMD is not affected by Meltdown, which means, there's no
> user/kernel pagetables split.
>
> And that also means, you have global TLB entries which means that if you
> look at that __native_flush_tlb_single() function, it needs to flush
> global TLB entries on CPUs with X86_FEATURE_INVPCID_SINGLE by doing an
> INVLPG in the kaiser_enabled=0 case. Errgo, the above hunk.

Makes sense.

Paolo