From: Sean Christopherson <firstname.lastname@example.org> To: Linus Torvalds <email@example.com> Cc: Paolo Bonzini <firstname.lastname@example.org>, Borislav Petkov <email@example.com>, Xiaoyao Li <firstname.lastname@example.org>, Linux Kernel Mailing List <email@example.com>, KVM list <firstname.lastname@example.org> Subject: Re: [GIT PULL] First batch of KVM changes for 5.6 merge window Date: Fri, 31 Jan 2020 10:53:42 -0800 [thread overview] Message-ID: <20200131185341.GA18946@linux.intel.com> (raw) In-Reply-To: <CAHk-=wjZTUq8u0HZUJ1mKZjb-haBFhX+mKcUv3Kdh9LQb8rg4g@mail.gmail.com> On Fri, Jan 31, 2020 at 10:01:37AM -0800, Linus Torvalds wrote: > On Thu, Jan 30, 2020 at 10:20 AM Paolo Bonzini <email@example.com> wrote: > > > > Xiaoyao Li (3): > > KVM: VMX: Rename INTERRUPT_PENDING to INTERRUPT_WINDOW > > KVM: VMX: Rename NMI_PENDING to NMI_WINDOW > > KVM: VMX: Fix the spelling of CPU_BASED_USE_TSC_OFFSETTING > > So in the meantime, on the x86 merge window side, we have this: > > b39033f504a7 ("KVM: VMX: Use VMX_FEATURE_* flags to define VMCS control bits") > > and while the above results in a conflict, that's not a problem. The > conflict was trivial to fix up. > > HOWEVER. > > It most definitely shows that the above renaming now means that the > names don't match. It didn't match 100% before either, but now the > differences are even bigger. The VMX_FEATURE_xyz bits have different > names than the CPU_BASED_xyz bits, and that seems a bit questionable. > > So I'm not convinced about the renaming. The spelling fix is good: it > actually now more closely resembles the VMCS_FEATURE bit that already > had OFFSETTING with two T's. > > But even that one isn't really the same even then. The CPU_BASED_xyz > thing has "USE_TSC_OFFSETTING", while the VMCS_FEATURE_xyz bit doesn't > have the "USE" part. > > And the actual renaming means that now we basically have > > CPU_BASED_INTR_WINDOW_EXITING > VMX_FEATURE_VIRTUAL_INTR_PENDING > > and > > CPU_BASED_NMI_WINDOW_EXITING > VMX_FEATURE_VIRTUAL_NMI_PENDING > > for the same bit definitions (yeah, the VMX_FEATURE bits obviously > have the offset in them, so it's not the same _value_, but it's a 1:1 > relationship between them). > > There are other (pre-existing) differences, but while fixing up the > merge conflict I really got the feeling that it's confusing and wrong > to basically use different naming for these things when they are about > the same bit. > > I don't care much which way it goes (maybe the VMX_FATURE_xyz bits > should be renamed instead of the other way around?) and I wonder what > the official documentation names are? Is there some standard here or > are people just picking names at random? > > The two commits both came from intel.com addresses, so hopefully there > can be some intel-sanctioned resolution on the naming? Please? Hrm. For *_WINDOW_EXITING versus VIRTUAL_*_PENDING, VMX_FEATURE_* should be renamed to use *_WINDOW_EXITING, as that's the nomenclature used by the SDM. I added the VMX_FEATURE_* names while KVM was still using VIRTUAL_*_PENDING, and neglected to go back and update the series, probably because I was in denial after lobbying to keep the non-SDM names and getting overruled :-). As for USE_TSC_OFFSETTING vs TSC_OFFSETTING, I'd like to keep the minor differences. VMX_FEATURES is intended to reflect the capabilities of the CPU, whereas the CPU_BASED/EXEC masks are effectively "commands" from software to hardware, e.g. "CPU has TSC offsetting" vs. "CPU, use TSC offsetting". Re-reading vmxfeatures.h, I botched a few names: USE_IO_BITMAPS and USE_MSR_BITMAPS shouldn't have the USE_ prefix, by my own capability vs. command argument. PAGE_MOD_LOGGING should simply be PML. I have no idea why I chose to (partially) expand the acronym. I assume the easiest thing would be send a cleanup patch for vmxfeatures.h and route it through the KVM tree?  https://lkml.kernel.org/r/20191206204747.GD5433@linux.intel.com/  https://firstname.lastname@example.org/
next prev parent reply other threads:[~2020-01-31 18:53 UTC|newest] Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-01-30 18:20 Paolo Bonzini 2020-01-31 18:01 ` Linus Torvalds 2020-01-31 18:53 ` Sean Christopherson [this message] 2020-01-31 19:03 ` Linus Torvalds 2020-01-31 21:08 ` Paolo Bonzini 2020-01-31 21:24 ` Borislav Petkov 2020-01-31 21:27 ` Paolo Bonzini 2020-01-31 19:35 ` pr-tracker-bot
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