Re: [PATCH 2/4 v3] x86: AMD: Add hardware-enforced cache coherency as a CPUID feature

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On 9/11/20 4:33 PM, Borislav Petkov wrote:
+ Tom.

On Fri, Sep 11, 2020 at 07:25:59PM +0000, Krish Sadhukhan wrote:
+#define X86_FEATURE_HW_CACHE_COHERENCY (11*32+ 7) /* AMD hardware-enforced cache coherency */

so before you guys paint the bikeshed all kinds of colors :), Tom (CCed)
is digging out the official name. (If it is even uglier, we might keep
on bikeshedding...).

I believe the official name is something like CoherencyEnforced. Since it's under the 0x8000001f leaf (AMD Secure Encryption), it means that coherency is enforced between the same physical address when referenced with or without the encryption bit (bare metal or in a guest).

So I kind of like the X86_FEATURE_SME_COHERENT suggestion by Dave, even if it also applies to SEV.

Thanks,
Tom


Once you have that, add the "" after the comment - like
X86_FEATURE_FENCE_SWAPGS_USER, for example, so that it doesn't show in
/proc/cpuinfo as luserspace doesn't care about hw coherency between enc
memory.

Thx.




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