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Subject: Re: [PATCH 2/6] KVM: mmu: also return page from gfn_to_pfn
To:     Nicholas Piggin <npiggin@gmail.com>,
        Aleksandar Markovic <aleksandar.qemu.devel@gmail.com>,
        Huacai Chen <chenhuacai@kernel.org>,
        Marc Zyngier <maz@kernel.org>,
        Paul Mackerras <paulus@ozlabs.org>,
        David Stevens <stevensd@chromium.org>,
        Zhenyu Wang <zhenyuw@linux.intel.com>,
        Zhi Wang <zhi.a.wang@intel.com>
Cc:     Alexandru Elisei <alexandru.elisei@arm.com>,
        dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org,
        intel-gvt-dev@lists.freedesktop.org,
        James Morse <james.morse@arm.com>,
        Jim Mattson <jmattson@google.com>,
        Joerg Roedel <joro@8bytes.org>, kvmarm@lists.cs.columbia.edu,
        kvm-ppc@vger.kernel.org, kvm@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
        Sean Christopherson <seanjc@google.com>,
        Suzuki K Poulose <suzuki.poulose@arm.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Will Deacon <will@kernel.org>
References: <20210624035749.4054934-1-stevensd@google.com>
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 <201b68a7-10ea-d656-0c1e-5511b1f22674@redhat.com>
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From:   Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <bbbd7334-5311-a7b4-5dec-8bc606f1d6c9@redhat.com>
Date:   Thu, 24 Jun 2021 12:13:52 +0200
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On 24/06/21 11:57, Nicholas Piggin wrote:
>> Needing kvm_pfn_page_unwrap is a sign that something might be buggy, so
>> it's a good idea to move the short name to the common case and the ugly
>> kvm_pfn_page_unwrap(gfn_to_pfn(...)) for the weird one.  In fact I'm not
>> sure there should be any kvm_pfn_page_unwrap in the end.
>
> If all callers were updated that is one thing, but from the changelog
> it sounds like that would not happen and there would be some gfn_to_pfn
> users left over.

In this patches there are, so yeah the plan is to always change the 
callers to the new way.

> But yes in the end you would either need to make gfn_to_pfn never return
> a page found via follow_pte, or change all callers to the new way. If
> the plan is for the latter then I guess that's fine.