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Zeng Heng 47490bbb05 arm64: tlb: Flush walk cache when unsharing PMD tables 
[ Upstream commit c2ff4764e0 ]

When huge_pmd_unshare() is called to unshare a PMD table, the
tlb_unshare_pmd_ptdesc() function sets tlb->unshared_tables=true
but the aarch64 tlb_flush() only checked tlb->freed_tables to
determine whether to use TLBF_NONE (vae1is, invalidates walk
cache) or TLBF_NOWALKCACHE (vale1is, leaf-only).

This caused the stale PMD page table entry to remain in the walk cache
after unshare, potentially leading to incorrect page table walks.

Fix by including unshared_tables in the check, so that when
unsharing tables, TLBF_NONE is used and the walk cache is properly
invalidated.

Here is the detailed distinction between vae1is and vale1is:

| Instruction Combination  | Actual Invalidation Scope                         |
| ------------------------ | --------------------------------------------------|
| `VAE1IS`  + TTL=`0`      | All entries at all levels (full invalidation)     |
| `VAE1IS`  + TTL=`2` (L2) | Non-leaf at Level 0/1 + leaf at Level 2           |
| `VALE1IS` + TTL=`0`      | Leaf entries at all levels (non-leaf not cleared) |
| `VALE1IS` + TTL=`2` (L2) | Leaf entry at Level 2 only                        |

Signed-off-by: Zeng Heng <zengheng4@huawei.com>
Fixes: 8ce720d5bd ("mm/hugetlb: fix excessive IPI broadcasts when unsharing PMD tables using mmu_gather")
Cc: <stable@vger.kernel.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2026-06-19 13:33:47 +02:00
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README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.