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Fri, 09 Oct 2026 14:05:06 -0700 (PDT) From: Magnus Lindholm To: richard.henderson@linaro.org, mattst88@gmail.com, linux-kernel@vger.kernel.org, linux-alpha@vger.kernel.org Cc: linmag7@gmail.com, stable@vger.kernel.org Subject: [PATCH v4 5/8] alpha: fix the local TLB invalidate in flush_tlb_page() Date: Fri, 9 Oct 2026 23:03:50 +0200 Message-ID: <20261009210449.971057-6-linmag7@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261009210449.971057-1-linmag7@gmail.com> References: <20261009210449.971057-1-linmag7@gmail.com> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit flush_tlb_page() invalidates the calling CPU itself before asking the others, and gates that on current->active_mm. For a non-executable vma that means a targeted tbi(2, addr), which acts on the context currently loaded and is only guaranteed to invalidate the intended translations when the target mm's context is the loaded one. A lazy active_mm does not establish that, so as in ipi_flush_tlb_page() the target mm's stale translations can survive, and nothing forces the old ASN to be retired afterwards. Test current->mm instead. A lazy caller then takes the flush_tlb_other() branch added by the previous patch, retiring its local context. Adding that branch first preserves the local invalidate at every step, including on EV7 where a targeted tbi() against a foreign ASN appeared to work. Which callers reach here with a foreign mm depends on the configuration. folio_mkclean(), from the writeback flusher kworker that has no mm of its own, accounted for about half the calls during writeback of a shared mapping and none at all on anonymous memory. Those counts were measured with CONFIG_COMPACTION=n: with COMPACTION=y, asm/pgtable.h overrides ptep_clear_flush() to call migrate_flush_tlb_page(), which rendezvouses with every CPU and handles the context itself, so folio_mkclean() does not reach this function. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Cc: stable@vger.kernel.org Reviewed-by: Matt Turner Signed-off-by: Magnus Lindholm Message-ID: <20260923074903.862898-4-linmag7@gmail.com> --- arch/alpha/kernel/smp.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/alpha/kernel/smp.c b/arch/alpha/kernel/smp.c index e4ba0aab8a66..a5a42ae4a7d8 100644 --- a/arch/alpha/kernel/smp.c +++ b/arch/alpha/kernel/smp.c @@ -684,7 +684,8 @@ flush_tlb_page(struct vm_area_struct *vma, unsigned long addr) preempt_disable(); - if (mm == current->active_mm) { + /* As in ipi_flush_tlb_page(): a targeted tbi() needs MM current. */ + if (mm == current->mm) { flush_tlb_current_page(mm, vma, addr); if (atomic_read(&mm->mm_users) <= 1) { int cpu, this_cpu = smp_processor_id(); -- 2.43.0