On Mon, Feb 01, 2021 at 01:01:51PM +1300, Kai Huang wrote: > On Sat, 30 Jan 2021 15:20:54 +0200 Jarkko Sakkinen wrote: > > On Wed, Jan 27, 2021 at 12:18:32PM +1300, Kai Huang wrote: > > > On Tue, 2021-01-26 at 07:34 -0800, Dave Hansen wrote: > > > > On 1/26/21 1:30 AM, Kai Huang wrote: > > > > > From: Sean Christopherson <seanjc@xxxxxxxxxx> > > > > > > > > > > Add SGX1 and SGX2 feature flags, via CPUID.0x12.0x0.EAX, as scattered > > > > > features, since adding a new leaf for only two bits would be wasteful. > > > > > As part of virtualizing SGX, KVM will expose the SGX CPUID leafs to its > > > > > guest, and to do so correctly needs to query hardware and kernel support > > > > > for SGX1 and SGX2. > > > > > > > > It's also not _just_ exposing the CPUID leaves. There are some checks > > > > here when KVM is emulating some SGX instructions too, right? > > > > > > I would say trapping instead of emulating, but yes KVM will do more. However those > > > are quite details, and I don't think we should put lots of details here. Or perhaps > > > we can use 'for instance' as brief description: > > > > > > As part of virtualizing SGX, KVM will need to use the two flags, for instance, to > > > expose them to guest. > > > > > > ? > > > > > > > > > > > > diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h > > > > > index 84b887825f12..18b2d0c8bbbe 100644 > > > > > --- a/arch/x86/include/asm/cpufeatures.h > > > > > +++ b/arch/x86/include/asm/cpufeatures.h > > > > > @@ -292,6 +292,8 @@ > > > > > #define X86_FEATURE_FENCE_SWAPGS_KERNEL (11*32+ 5) /* "" LFENCE in kernel entry SWAPGS path */ > > > > > #define X86_FEATURE_SPLIT_LOCK_DETECT (11*32+ 6) /* #AC for split lock */ > > > > > #define X86_FEATURE_PER_THREAD_MBA (11*32+ 7) /* "" Per-thread Memory Bandwidth Allocation */ > > > > > +#define X86_FEATURE_SGX1 (11*32+ 8) /* Software Guard Extensions sub-feature SGX1 */ > > > > > +#define X86_FEATURE_SGX2 (11*32+ 9) /* Software Guard Extensions sub-feature SGX2 */ > > > > > > > > FWIW, I'm not sure how valuable it is to spell the SGX acronym out three > > > > times. Can't we use those bytes to put something more useful in that > > > > comment? > > > > > > I think we can remove comment for SGX1, since it is basically SGX. > > > > > > For SGX2, how about below? > > > > > > /* SGX Enclave Dynamic Memory Management */ > > > > (EDMM) > > Does EDMM obvious to everyone, instead of explicitly saying Enclave Dynamic > Memory Management? > > Also do you think we need a comment for SGX1 bit? I can add /* Basic SGX */, > but I am not sure whether it is required. I would put write the whole thing down and put EDMM to parentheses. For SGX1 I would put "Basic SGX features for enclave construction". /Jarkko
