From: Nicholas Piggin <npiggin@gmail.com>
To: Aleksandar Markovic <aleksandar.qemu.devel@gmail.com>,
Huacai Chen <chenhuacai@kernel.org>,
Marc Zyngier <maz@kernel.org>, Paul Mackerras <paulus@ozlabs.org>,
Paolo Bonzini <pbonzini@redhat.com>,
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>
Subject: Re: [PATCH 2/6] KVM: mmu: also return page from gfn_to_pfn
Date: Thu, 24 Jun 2021 20:17:42 +1000 [thread overview]
Message-ID: <1624529635.75a1ann91v.astroid@bobo.none> (raw)
In-Reply-To: <1624528342.s2ezcyp90x.astroid@bobo.none>
Excerpts from Nicholas Piggin's message of June 24, 2021 7:57 pm:
> Excerpts from Paolo Bonzini's message of June 24, 2021 7:42 pm:
>> On 24/06/21 10:52, Nicholas Piggin wrote:
>>>> For now, wrap all calls to gfn_to_pfn functions in the new helper
>>>> function. Callers which don't need the page struct will be updated in
>>>> follow-up patches.
>>> Hmm. You mean callers that do need the page will be updated? Normally
>>> if there will be leftover users that don't need the struct page then
>>> you would go the other way and keep the old call the same, and add a new
>>> one (gfn_to_pfn_page) just for those that need it.
>>
>> 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.
>
> 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.
Actually in that case anyway I don't see the need -- the existence of
gfn_to_pfn is enough to know it might be buggy. It can just as easily
be grepped for as kvm_pfn_page_unwrap. And are gfn_to_page cases also
vulernable to the same issue?
So I think it could be marked deprecated or something if not everything
will be converted in the one series, and don't need to touch all that
arch code with this patch.
Thanks,
Nick
next prev parent reply other threads:[~2021-06-24 10:17 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-24 3:57 [PATCH 0/6] KVM: Remove uses of struct page from x86 and arm64 MMU David Stevens
2021-06-24 3:57 ` [PATCH 1/6] KVM: x86/mmu: release audited pfns David Stevens
2021-06-24 8:43 ` Nicholas Piggin
2021-06-24 9:43 ` Paolo Bonzini
2021-06-24 15:36 ` Sean Christopherson
2021-06-24 3:57 ` [PATCH 2/6] KVM: mmu: also return page from gfn_to_pfn David Stevens
2021-06-24 8:52 ` Nicholas Piggin
2021-06-24 9:42 ` Paolo Bonzini
2021-06-24 9:57 ` Nicholas Piggin
2021-06-24 10:13 ` Paolo Bonzini
2021-06-24 10:17 ` Nicholas Piggin [this message]
2021-06-24 10:21 ` Paolo Bonzini
2021-06-24 10:42 ` Nicholas Piggin
2021-06-24 9:40 ` Marc Zyngier
2021-06-24 3:57 ` [PATCH 3/6] KVM: x86/mmu: avoid struct page in MMU David Stevens
2021-06-24 7:31 ` Paolo Bonzini
2021-06-24 8:58 ` Nicholas Piggin
2021-06-24 10:06 ` Marc Zyngier
2021-06-24 10:17 ` Paolo Bonzini
2021-06-24 10:43 ` Nicholas Piggin
2021-06-24 3:57 ` [PATCH 4/6] KVM: arm64/mmu: " David Stevens
2021-06-24 10:43 ` Marc Zyngier
2021-06-24 3:57 ` [PATCH 5/6] KVM: mmu: remove over-aggressive warnings David Stevens
2021-06-24 3:57 ` [PATCH 6/6] drm/i915/gvt: use gfn_to_pfn's page instead of pfn David Stevens
2021-06-24 4:28 ` David Stevens
2021-06-24 6:57 ` [PATCH 0/6] KVM: Remove uses of struct page from x86 and arm64 MMU Paolo Bonzini
2021-06-24 10:34 ` Nicholas Piggin
2021-06-24 11:42 ` Nicholas Piggin
2021-06-24 12:00 ` Paolo Bonzini
2021-06-24 12:41 ` Paolo Bonzini
2021-06-24 12:57 ` Nicholas Piggin
2021-06-24 15:35 ` Paolo Bonzini
2021-06-25 0:20 ` Nicholas Piggin
2021-06-25 7:44 ` Christian Borntraeger
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