Messages in this thread | | | Subject | Re: [PATCH] kvm: arm: Fix handling of stage2 huge mappings | From | Suzuki K Poulose <> | Date | Wed, 20 Mar 2019 10:23:39 +0000 |
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Marc,
On 20/03/2019 10:11, Marc Zyngier wrote: > On Wed, 20 Mar 2019 09:44:38 +0000 > Suzuki K Poulose <suzuki.poulose@arm.com> wrote: > >> Hi Marc, >> >> On 20/03/2019 08:15, Marc Zyngier wrote: >>> Hi Suzuki, >>> >>> On Tue, 19 Mar 2019 14:11:08 +0000, >>> Suzuki K Poulose <suzuki.poulose@arm.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@huawei.com> >>>> Cc: Zheng Xiang <zhengxiang9@huawei.com> >>>> Cc: Zhengui Yu <yuzenghui@huawei.com> >>>> Cc: Marc Zyngier <marc.zyngier@arm.com> >>>> Cc: Christoffer Dall <christoffer.dall@arm.com> >>>> Signed-off-by: Suzuki K Poulose ...
>>>> + if (!pmd_thp_or_huge(old_pmd)) { >>>> + unmap_stage2_range(kvm, addr & S2_PMD_MASK, S2_PMD_SIZE); >>>> + goto retry; >>>
>>>> + if (!stage2_pud_huge(kvm, old_pud)) { >>>> + unmap_stage2_range(kvm, addr & S2_PUD_MASK, S2_PUD_SIZE); >>>
>> We should really get rid of the S2_P{U/M}D_* definitions, as they are >> always the same as the host. The only thing that changes is the PGD size >> which varies according to the IPA and the concatenation. >>
Also what do you think about using P{M,U}D_* instead of S2_P{M,U}D_* above ? I could make that change with the respin.
> > Sure, feel free to send a fixed version. I'll drop the currently queued > patch. >
Thanks. Sorry for the trouble.
Cheers Suzuki
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