linux-kernel - Re: [PATCH v2] kvm: arm: Fix handling of stage2 huge mappings

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Message-ID: <20190320173154.6cfc7072@why.wild-wind.fr.eu.org>
Date:   Wed, 20 Mar 2019 17:31:54 +0000
From:   Marc Zyngier <marc.zyngier@....com>
To:     Suzuki K Poulose <suzuki.poulose@....com>
Cc:     <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <kvm@...r.kernel.org>,
        <kvmarm@...ts.cs.columbia.edu>, <will.deacon@....com>,
        <catalin.marinas@....com>, <james.morse@....com>,
        <julien.thierry@....com>, <wanghaibin.wang@...wei.com>,
        <lious.lilei@...ilicon.com>, <lishuo1@...ilicon.com>,
        <zhengxiang9@...wei.com>, <yuzenghui@...wei.com>,
        Christoffer Dall <christoffer.dall@....com>
Subject: Re: [PATCH v2] kvm: arm: Fix handling of stage2 huge mappings

On Wed, 20 Mar 2019 14:57:19 +0000
Suzuki K Poulose <suzuki.poulose@....com> wrote:

> We rely on the mmu_notifier call backs to handle the split/merge
> of huge pages and thus we are guaranteed that, while creating a
> block mapping, either the entire block is unmapped at stage2 or it
> is missing permission.
> 
> However, we miss a case where the block mapping is split for dirty
> logging case and then could later be made block mapping, if we cancel the
> dirty logging. This not only creates inconsistent TLB entries for
> the pages in the the block, but also leakes the table pages for
> PMD level.
> 
> Handle this corner case for the huge mappings at stage2 by
> unmapping the non-huge mapping for the block. This could potentially
> release the upper level table. So we need to restart the table walk
> once we unmap the range.
> 
> Fixes : ad361f093c1e31d ("KVM: ARM: Support hugetlbfs backed huge pages")
> Reported-by: Zheng Xiang <zhengxiang9@...wei.com>
> Cc: Zheng Xiang <zhengxiang9@...wei.com>
> Cc: Zhenghui Yu <yuzenghui@...wei.com>
       ^
> Cc: Marc Zyngier <marc.zyngier@....com>
> Cc: Christoffer Dall <christoffer.dall@....com>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>

Applied, with Zenghui's name fixed.

Thanks,

	M.
-- 
Without deviation from the norm, progress is not possible.