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Message-ID: <628dcac82f5b1113d50b9d59ef58267f744ec867.camel@intel.com>
Date: Fri, 7 Jun 2024 20:06:42 +0000
From: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To: "pbonzini@...hat.com" <pbonzini@...hat.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 08/15] KVM: x86/tdp_mmu: Introduce KVM MMU root types
to specify page table type
On Fri, 2024-06-07 at 10:10 +0200, Paolo Bonzini wrote:
> On Thu, May 30, 2024 at 11:07 PM Rick Edgecombe
> <rick.p.edgecombe@...el.com> wrote:
> > +enum kvm_tdp_mmu_root_types {
> > + KVM_VALID_ROOTS = BIT(0),
> > +
> > + KVM_ANY_ROOTS = 0,
> > + KVM_ANY_VALID_ROOTS = KVM_VALID_ROOTS,
>
> I would instead define it as
>
> KVM_INVALID_ROOTS = BIT(0),
> KVM_VALID_ROOTS = BIT(1),
> KVM_ALL_ROOTS = KVM_VALID_ROOTS | KVM_INVALID_ROOTS,
>
> and then
>
> if (root->role.invalid)
> return types & KVM_INVALID_ROOTS;
> else
> return types & KVM_VALID_ROOTS;
>
> Then in the next patch you can do
>
> KVM_INVALID_ROOTS = BIT(0),
> - KVM_VALID_ROOTS = BIT(1),
> + KVM_DIRECT_ROOTS = BIT(1),
> + KVM_MIRROR_ROOTS = BIT(2),
> + KVM_VALID_ROOTS = KVM_DIRECT_ROOTS | KVM_MIRROR_ROOTS,
> KVM_ALL_ROOTS = KVM_VALID_ROOTS | KVM_INVALID_ROOTS,
>
> and likewise
>
> if (root->role.invalid)
> return types & KVM_INVALID_ROOTS;
> else if (likely(!is_mirror_sp(root)))
> return types & KVM_DIRECT_ROOTS;
> else
> return types & KVM_MIRROR_ROOTS;
>
> This removes the need for KVM_ANY_VALID_ROOTS (btw I don't know if
> it's me, but ALL sounds more grammatical than ANY in this context). So
> the resulting code should be a bit clearer.
>
> Apart from this small tweak, the overall idea is really good.
Yes, this makes more sense. Thanks.
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