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V" , Andrew Morton , Nick Piggin , Peter Zijlstra , Catalin Marinas , Paul Walmsley , Palmer Dabbelt , Albert Ou , Arnd Bergmann , linux-arch@vger.kernel.org, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, Nadav Amit , Andrea Arcangeli , Andy Lutomirski , Dave Hansen , Thomas Gleixner , Yu Zhao , x86@kernel.org Subject: Re: [PATCH 1/2] mm/tlb: fix fullmm semantics Message-ID: <20240103175001.GF5954@willie-the-truck> References: <20231228084642.1765-1-jszhang@kernel.org> <20231228084642.1765-2-jszhang@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20231228084642.1765-2-jszhang@kernel.org> User-Agent: Mutt/1.10.1 (2018-07-13) X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: BF5F3A0023 X-Stat-Signature: od8wa169pjmxty7jntbshr7k5j84juon X-Rspam-User: X-HE-Tag: 1704304213-384115 X-HE-Meta: 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 AEOiNJzg b6CwQvipXGJvMcleUyi7ZF8KJvgPADuzu25adA3Q9A09b9i1MqYmkj/RJU6xtoUVZl2uU56MBu0WI7nbi56osoIEV4O1obKznUiVqWvSOaDP4KnHXpzYcrOh7RJSPlrBrxeGUUB8NhaBefQUGdqJWXUeT4VNxlu+oincJSRbAeaH7fXPcZxhAr6MuzQBhKspmjpzphJU8IFgVOyrpNn1hzqz4c/3SZuSyPdt8BP0ojg4f9p9U11adZ4Bx/Fgg89cyjtSnAJcQ+UXnjbey9nm2CPM+pg7rqHyLMGwcVjWhabOS1eeVdE/me+8Zt1s25VhtSnAn/toSCW9p/6f6tLX/BdzfgGZdXjjCNJcgSUzYdt2FSOMC8P+JAuwDZMiPhxT9mZ8jw8WvrMQfueQGxadSSTUBw93kOb7OiMrWL4wpDp6yBwsA2iEQkGWObUU0aBS/xfO5PNCyfW048mqhDauIiv9mhcD4fIcscdguNqdglkYjT/s= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Dec 28, 2023 at 04:46:41PM +0800, Jisheng Zhang wrote: > From: Nadav Amit > > fullmm in mmu_gather is supposed to indicate that the mm is torn-down > (e.g., on process exit) and can therefore allow certain optimizations. > However, tlb_finish_mmu() sets fullmm, when in fact it want to say that > the TLB should be fully flushed. > > Change tlb_finish_mmu() to set need_flush_all and check this flag in > tlb_flush_mmu_tlbonly() when deciding whether a flush is needed. > > At the same time, bring the arm64 fullmm on process exit optimization back. > > Signed-off-by: Nadav Amit > Signed-off-by: Jisheng Zhang > Cc: Andrea Arcangeli > Cc: Andrew Morton > Cc: Andy Lutomirski > Cc: Dave Hansen > Cc: Peter Zijlstra > Cc: Thomas Gleixner > Cc: Will Deacon > Cc: Yu Zhao > Cc: Nick Piggin > Cc: x86@kernel.org > --- > arch/arm64/include/asm/tlb.h | 5 ++++- > include/asm-generic/tlb.h | 2 +- > mm/mmu_gather.c | 2 +- > 3 files changed, 6 insertions(+), 3 deletions(-) > > diff --git a/arch/arm64/include/asm/tlb.h b/arch/arm64/include/asm/tlb.h > index 846c563689a8..6164c5f3b78f 100644 > --- a/arch/arm64/include/asm/tlb.h > +++ b/arch/arm64/include/asm/tlb.h > @@ -62,7 +62,10 @@ static inline void tlb_flush(struct mmu_gather *tlb) > * invalidating the walk-cache, since the ASID allocator won't > * reallocate our ASID without invalidating the entire TLB. > */ > - if (tlb->fullmm) { > + if (tlb->fullmm) > + return; > + > + if (tlb->need_flush_all) { > if (!last_level) > flush_tlb_mm(tlb->mm); > return; Why isn't the 'last_level' check sufficient here? In other words, when do we perform a !last_level invalidation with 'fullmm' set outside of teardown? Will