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From:   Yanan Wang <wangyanan55@huawei.com>
To:     <linux-kernel@vger.kernel.org>,
        <linux-arm-kernel@lists.infradead.org>,
        Marc Zyngier <maz@kernel.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>,
        James Morse <james.morse@arm.com>,
        "Julien Thierry" <julien.thierry.kdev@gmail.com>,
        Suzuki K Poulose <suzuki.poulose@arm.com>,
        Gavin Shan <gshan@redhat.com>,
        Quentin Perret <qperret@google.com>
CC:     <wanghaibin.wang@huawei.com>, <yezengruan@huawei.com>,
        <zhukeqian1@huawei.com>, <yuzenghui@huawei.com>,
        <jiangkunkun@huawei.com>, <wangjingyi11@huawei.com>,
        <lushenming@huawei.com>, Yanan Wang <wangyanan55@huawei.com>
Subject: [RFC PATCH 0/3] Fix several bugs in KVM stage 2 translation
Date:   Mon, 30 Nov 2020 20:18:44 +0800
Message-ID: <20201130121847.91808-1-wangyanan55@huawei.com>
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Several problems about KVM stage 2 translation were found when testing based
on the mainline code. The following is description of the problems and the
corresponding patchs.

When installing a new pte entry or updating an old valid entry in stage 2
translation, we use get_page()/put_page() to record page_count of the page-table
pages. PATCH 1/3 aims to fix incorrect use of get_page()/put_page() in stage 2,
which might make page-table pages unable to be freed when unmapping a range.

When dirty logging of a guest with hugepages is finished, we should merge tables
back into a block entry if adjustment of huge mapping is found necessary.
In addition to installing the block entry, mapping of the lower-levels for the
block should also be unmapped to avoid multiple TLB entries.
PATCH 2/3 adds unmap operation when merge tables into a block entry.

The rewrite of page-table code and fault handling add two different handlers
for "just relaxing permissions" and "map by stage2 page-table walk", that's
great improvement. Yet, in function user_mem_abort(), conditions where we choose
the above two fault handlers are not strictly distinguished. This will causes
guest errors such as infinite-loop (soft lockup will occur in result), because of
calling the inappropriate fault handler. So, a solution that can strictly
distinguish conditions is introduced in PATCH 3/3.

Yanan Wang (3):
  KVM: arm64: Fix possible memory leak in kvm stage2
  KVM: arm64: Fix handling of merging tables into a block entry
  KVM: arm64: Add usage of stage 2 fault lookup level in
    user_mem_abort()

 arch/arm64/include/asm/esr.h         |  1 +
 arch/arm64/include/asm/kvm_emulate.h |  5 +++++
 arch/arm64/kvm/hyp/pgtable.c         | 22 +++++++++++++++++-----
 arch/arm64/kvm/mmu.c                 | 11 +++++++++--
 4 files changed, 32 insertions(+), 7 deletions(-)

-- 
2.19.1