linux-kernel - Re: [PATCH v2 06/15] KVM: x86/mmu: Support GFN direct mask

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Date: Sat, 8 Jun 2024 10:52:24 +0200
From: Paolo Bonzini <pbonzini@...hat.com>
To: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
Cc: "seanjc@...gle.com" <seanjc@...gle.com>, "Huang, Kai" <kai.huang@...el.com>, 
	"sagis@...gle.com" <sagis@...gle.com>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "Aktas, Erdem" <erdemaktas@...gle.com>, 
	"Zhao, Yan Y" <yan.y.zhao@...el.com>, "dmatlack@...gle.com" <dmatlack@...gle.com>, 
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>, "Yamahata, Isaku" <isaku.yamahata@...el.com>, 
	"isaku.yamahata@...il.com" <isaku.yamahata@...il.com>
Subject: Re: [PATCH v2 06/15] KVM: x86/mmu: Support GFN direct mask

On Fri, Jun 7, 2024 at 8:39 PM Edgecombe, Rick P
<rick.p.edgecombe@...el.com> wrote:
> > > +       return kvm_gfn_direct_mask(kvm);
> >
> > Ok, please excuse me again for being fussy on the naming. Typically I
> > think of a "mask" as something that you check against, or something
> > that you do x &~ mask, not as something that you add. Maybe
> > kvm_gfn_root_offset and gfn_direct_offset?
>
> As for the name, I guess I'd be less keen on "offset" because it's not clear
> that it is a power-of-two value that can be used with bitwise operations.
>
> I'm not sure what the "fixed" adds and it makes it longer. Also, many PTE bits
> cannot be moved and they are not referred to as fixed, where the shared bit
> actually *can* be moved via GPAW (not that the MMU code cares about that
> though).
>
> Just "bits" sounds better to me, so maybe I'll try?
> kvm_gfn_direct_bits()
> kvm_gfn_root_bits()

Yep, kvm_gfn_direct_bits and kvm_gfn_root_bits are good.

Paolo