linux-kernel - Re: [PATCH v12 34/84] KVM: Add a helper to lookup a pfn without grabbing a reference

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Message-ID: <63c41e25-2523-4397-96b4-557394281443@redhat.com>
Date: Tue, 30 Jul 2024 12:41:31 +0200
From: Paolo Bonzini <pbonzini@...hat.com>
To: Sean Christopherson <seanjc@...gle.com>, Marc Zyngier <maz@...nel.org>,
 Oliver Upton <oliver.upton@...ux.dev>, Tianrui Zhao
 <zhaotianrui@...ngson.cn>, Bibo Mao <maobibo@...ngson.cn>,
 Huacai Chen <chenhuacai@...nel.org>, Michael Ellerman <mpe@...erman.id.au>,
 Anup Patel <anup@...infault.org>, Paul Walmsley <paul.walmsley@...ive.com>,
 Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>,
 Christian Borntraeger <borntraeger@...ux.ibm.com>,
 Janosch Frank <frankja@...ux.ibm.com>,
 Claudio Imbrenda <imbrenda@...ux.ibm.com>
Cc: kvm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 kvmarm@...ts.linux.dev, loongarch@...ts.linux.dev,
 linux-mips@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
 kvm-riscv@...ts.infradead.org, linux-riscv@...ts.infradead.org,
 linux-kernel@...r.kernel.org, David Matlack <dmatlack@...gle.com>,
 David Stevens <stevensd@...omium.org>
Subject: Re: [PATCH v12 34/84] KVM: Add a helper to lookup a pfn without
 grabbing a reference

On 7/27/24 01:51, Sean Christopherson wrote:
> Add a kvm_follow_pfn() wrapper, kvm_lookup_pfn(), to allow looking up a
> gfn=>pfn mapping without the caller getting a reference to any underlying
> page.  The API will be used in flows that want to know if a gfn points at
> a valid pfn, but don't actually need to do anything with the pfn.

Can you rename the function kvm_gfn_has_pfn(), or 
kvm_gfn_can_be_mapped(), and make it return a bool?

(As an aside, I wonder if reexecute_instruction() could just use 
kvm_is_error_hva(kvm_vcpu_gfn_to_hva(vcpu, gpa_to_gfn(gpa)) instead of 
going all the way to a pfn.  But it's ok to be more restrictive).

Paolo