From: Paolo Bonzini <pbonzini@redhat.com>
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>,
David Stevens <stevensd@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 0/6] KVM: Remove uses of struct page from x86 and arm64 MMU
Date: Thu, 24 Jun 2021 17:35:25 +0200 [thread overview]
Message-ID: <81d99029-ec40-19c5-5647-20607d78dab0@redhat.com> (raw)
In-Reply-To: <1624539354.6zggpdrdbw.astroid@bobo.none>
On 24/06/21 14:57, Nicholas Piggin wrote:
> KVM: Fix page ref underflow for regions with valid but non-refcounted pages
It doesn't really fix the underflow, it disallows mapping them in the
first place. Since in principle things can break, I'd rather be
explicit, so let's go with "KVM: do not allow mapping valid but
non-reference-counted pages".
> It's possible to create a region which maps valid but non-refcounted
> pages (e.g., tail pages of non-compound higher order allocations). These
> host pages can then be returned by gfn_to_page, gfn_to_pfn, etc., family
> of APIs, which take a reference to the page, which takes it from 0 to 1.
> When the reference is dropped, this will free the page incorrectly.
>
> Fix this by only taking a reference on the page if it was non-zero,
s/on the page/on valid pages/ (makes clear that invalid pages are fine
without refcounting).
Thank you *so* much, I'm awful at Linux mm.
Paolo
> which indicates it is participating in normal refcounting (and can be
> released with put_page).
>
> Signed-off-by: Nicholas Piggin<npiggin@gmail.com>
next prev parent reply other threads:[~2021-06-24 15:35 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
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 [this message]
2021-06-25 0:20 ` Nicholas Piggin
2021-06-25 7:44 ` Christian Borntraeger
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