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b=qRpyAbZFZmLuBkW96iFZWGvYTcvU6yEUgg3li9k9FXDXVxQ1vFE7pjAOuGS4yFqPhW5FQjLobrvvGBvTBcCpNatpvEl0S/asGqvk0C9b94o0AxguAddLosmRLiPl/WvNLyrhrYYrdQSnT37ZqxKQJLvAIrErFqG8guS/Iwa3P+k= Received: from DESKTOP-5N7EMDA(mailfrom:ying.huang@linux.alibaba.com fp:SMTPD_---0WqmTUwB_1761129260 cluster:ay36) by smtp.aliyun-inc.com; Wed, 22 Oct 2025 18:34:20 +0800 From: "Huang, Ying" To: Barry Song <21cnbao@gmail.com> Cc: Catalin Marinas , Will Deacon , Andrew Morton , David Hildenbrand , Lorenzo Stoakes , Vlastimil Babka , Zi Yan , Baolin Wang , Ryan Roberts , Yang Shi , "Christoph Lameter (Ampere)" , Dev Jain , Anshuman Khandual , Yicong Yang , Kefeng Wang , Kevin Brodsky , Yin Fengwei , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH -v2 2/2] arm64, tlbflush: don't TLBI broadcast if page reused in write fault In-Reply-To: (Barry Song's message of "Wed, 22 Oct 2025 22:55:05 +1300") References: <20251013092038.6963-1-ying.huang@linux.alibaba.com> <20251013092038.6963-3-ying.huang@linux.alibaba.com> <87a51jfl44.fsf@DESKTOP-5N7EMDA> <871pmv9unr.fsf@DESKTOP-5N7EMDA> <875xc78es0.fsf@DESKTOP-5N7EMDA> <87a51j6zg7.fsf@DESKTOP-5N7EMDA> Date: Wed, 22 Oct 2025 18:34:19 +0800 Message-ID: <87ms5j4444.fsf@DESKTOP-5N7EMDA> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Stat-Signature: aksj9dc9q38d4gk739op1s6gpa3ctoah X-Rspamd-Queue-Id: 1DDD4100006 X-Rspamd-Server: rspam09 X-HE-Tag: 1761129264-850287 X-HE-Meta: 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 Ip/+/V1o JrPZF+xlNLQT94+RhKMjR3CcU4GIhMyq8mmq/Ezf4BvLL+1eQtbLWE16aJOiiuc5sp/nSO05IIZzBPcCbQyO2dUMBsZd0vk9PUCB4Jz6uzhtQg+vGJXuNcngMqN2viXLoFGBeN6a8qnl5MZLX6K48Eewek2uuUEvq0rR+J1wG+J2vHk/hXXM9fWEs6RQMcfjMsbi6AYxuXEGP05W5m9zKD0/I5QrM6ZZYcOc/+1M5U4o/X8Ns9GKSsrxawA== 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: Barry Song <21cnbao@gmail.com> writes: > On Wed, Oct 22, 2025 at 10:46=E2=80=AFPM Huang, Ying > wrote: > >> > >> > I agree. Yet the ish barrier can still avoid the page faults during CP= U0's PTL. >> >> IIUC, you think that dsb(ish) compared with dsb(nsh) can accelerate >> memory writing (visible to other CPUs). TBH, I suspect that this is the >> case. > > Why? In any case, nsh is not a smp domain. I think dsb(ish) will be slower than dsb(nsh) in theory. I guess that dsb just wait for the memory write to be visible in the specified shareability domain instead of making write faster. > I believe a dmb(ishst) is sufficient to ensure that the new PTE writes > are visible dmb(ishst) (smp_wmb()) should pair with dmb(ishld) (smp_rmb()). > to other CPUs. I=E2=80=99m not quite sure why the current flush code uses= dsb(ish); > it seems like overkill. dsb(ish) here is used for tlbi(XXis) broadcast. It waits until the page table change is visible to the page table walker of the remote CPU. --- Best Regards, Huang, Ying