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SubjectRe: [PATCH v2 0/3] Fix several bugs in KVM stage 2 translation
On Wed, Dec 02, 2020 at 04:10:31AM +0800, Yanan Wang wrote:
> 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, we should not only free the non-huge
> page-table pages but also invalidate all the TLB entries of non-huge mappings for
> the block. PATCH 2/3 adds enough TLBI when merging 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
> good 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.

For the series:

Acked-by: Will Deacon <will@kernel.org>

Thanks for reporting these, helping me to understand the issues and then
spinning a v2 so promptly.

Will

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