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imf15.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=arm.com; spf=pass (imf15.hostedemail.com: domain of ryan.roberts@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=ryan.roberts@arm.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1702381629; a=rsa-sha256; cv=none; b=ro+2NMF5fSRsHv0gJ/lL+ljCup+WE5DXrHP6bSXUzbZmYYAXjlAoI0WldjC6EOenICwJ2+ i51fN0ek+139wUEym+FgZC2gk8iFhltQbbEMxrnPaL53VayuQaHhkPM+EHGoLBVxNOQgT/ cGnWZYf/xwiCvx8V99DTAQYvcTi/SkU= Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 61161143D; Tue, 12 Dec 2023 03:47:54 -0800 (PST) Received: from [10.1.39.183] (XHFQ2J9959.cambridge.arm.com [10.1.39.183]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id B122A3F762; Tue, 12 Dec 2023 03:47:04 -0800 (PST) Message-ID: <0969c413-bf40-4c46-9f1e-a92101ff2d2e@arm.com> Date: Tue, 12 Dec 2023 11:47:03 +0000 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 12/15] arm64/mm: Split __flush_tlb_range() to elide trailing DSB To: Will Deacon Cc: Catalin Marinas , Ard Biesheuvel , Marc Zyngier , Oliver Upton , James Morse , Suzuki K Poulose , Zenghui Yu , Andrey Ryabinin , Alexander Potapenko , Andrey Konovalov , Dmitry Vyukov , Vincenzo Frascino , Andrew Morton , Anshuman Khandual , Matthew Wilcox , Yu Zhao , Mark Rutland , David Hildenbrand , Kefeng Wang , John Hubbard , Zi Yan , Barry Song <21cnbao@gmail.com>, Alistair Popple , Yang Shi , linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20231204105440.61448-1-ryan.roberts@arm.com> <20231204105440.61448-13-ryan.roberts@arm.com> <20231212113517.GA28857@willie-the-truck> Content-Language: en-GB From: Ryan Roberts In-Reply-To: <20231212113517.GA28857@willie-the-truck> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 5A388A000E X-Rspam-User: X-Rspamd-Server: rspam04 X-Stat-Signature: jrruonj6ybb58du7dzen3k6sugzoixek X-HE-Tag: 1702381629-732053 X-HE-Meta: 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 fG0/kB+e aFq009s+dDC26FcdPf2f8SDu/I/y8hwYccsrZ5V9F5mzvsqZpdRXPejPZbgC0LPNa9feW0q7nidntHJtGntYYXsHYmLFDj4PiXaYOHw10bQQyGVA//3nx34MMbcGd0Ot5+7r0JHreZSeA2FmjqYuYfKbMAXTcOVZTtVlYedQ//p9yeZozA42/rAkSh6fGhS3hwx1YF7/6YE/DZyZwaSJxby6rqiLknnA1NV4ZGKOAGH+3pYHtfvjyC6RFKafyPjBHXRelLkFhjH+M8uTt7HwamcCXMjOvCxkecxEXYrEgaSNM6U43EaT3ZUizxb1yeNRDjfV6CkvBMvUKxZs= 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 12/12/2023 11:35, Will Deacon wrote: > On Mon, Dec 04, 2023 at 10:54:37AM +0000, Ryan Roberts wrote: >> Split __flush_tlb_range() into __flush_tlb_range_nosync() + >> __flush_tlb_range(), in the same way as the existing flush_tlb_page() >> arrangement. This allows calling __flush_tlb_range_nosync() to elide the >> trailing DSB. Forthcoming "contpte" code will take advantage of this >> when clearing the young bit from a contiguous range of ptes. >> >> Signed-off-by: Ryan Roberts >> --- >> arch/arm64/include/asm/tlbflush.h | 13 +++++++++++-- >> 1 file changed, 11 insertions(+), 2 deletions(-) >> >> diff --git a/arch/arm64/include/asm/tlbflush.h b/arch/arm64/include/asm/tlbflush.h >> index bb2c2833a987..925ef3bdf9ed 100644 >> --- a/arch/arm64/include/asm/tlbflush.h >> +++ b/arch/arm64/include/asm/tlbflush.h >> @@ -399,7 +399,7 @@ do { \ >> #define __flush_s2_tlb_range_op(op, start, pages, stride, tlb_level) \ >> __flush_tlb_range_op(op, start, pages, stride, 0, tlb_level, false) >> >> -static inline void __flush_tlb_range(struct vm_area_struct *vma, >> +static inline void __flush_tlb_range_nosync(struct vm_area_struct *vma, >> unsigned long start, unsigned long end, >> unsigned long stride, bool last_level, >> int tlb_level) >> @@ -431,10 +431,19 @@ static inline void __flush_tlb_range(struct vm_area_struct *vma, >> else >> __flush_tlb_range_op(vae1is, start, pages, stride, asid, tlb_level, true); >> >> - dsb(ish); >> mmu_notifier_arch_invalidate_secondary_tlbs(vma->vm_mm, start, end); >> } >> >> +static inline void __flush_tlb_range(struct vm_area_struct *vma, >> + unsigned long start, unsigned long end, >> + unsigned long stride, bool last_level, >> + int tlb_level) >> +{ >> + __flush_tlb_range_nosync(vma, start, end, stride, >> + last_level, tlb_level); >> + dsb(ish); >> +} > > Hmm, are you sure it's safe to defer the DSB until after the secondary TLB > invalidation? It will have a subtle effect on e.g. an SMMU participating > in broadcast TLB maintenance, because now the ATC will be invalidated > before completion of the TLB invalidation and it's not obviously safe to me. I'll be honest; I don't know that it's safe. The notifier calls turned up during a rebase and I stared at it for a while, before eventually concluding that I should just follow the existing pattern in __flush_tlb_page_nosync(): That one calls the mmu notifier without the dsb, then flush_tlb_page() does the dsb after. So I assumed it was safe. If you think it's not safe, I guess there is a bug to fix in __flush_tlb_page_nosync()? > > Will