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Wed, 22 Oct 2025 02:55:16 -0700 (PDT) MIME-Version: 1.0 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> In-Reply-To: <87a51j6zg7.fsf@DESKTOP-5N7EMDA> From: Barry Song <21cnbao@gmail.com> Date: Wed, 22 Oct 2025 22:55:05 +1300 X-Gm-Features: AS18NWC0tC5R_nmZzildYKBiK0mP4MFijg1oZBWOAHCcOJkrnfuDN46LvjeO47c Message-ID: Subject: Re: [PATCH -v2 2/2] arm64, tlbflush: don't TLBI broadcast if page reused in write fault To: "Huang, Ying" 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 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 98988C0008 X-Rspamd-Server: rspam11 X-Rspam-User: X-Stat-Signature: 9fep4dxxpb4bjiitjkh58idbox9iqxfh X-HE-Tag: 1761126917-505539 X-HE-Meta: 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 tUp5rVZw PEnzcVK3moi3D5Sf7/1/snHuC7cSHPWYTt5Mi0I9RMJOyvdXNekz32QNZfjphABpAQHbFE7tRE6RoCcA11RVcCc8fEmfEuJnHt8w+omX6nObWsPMJKVPrDCnTVmdRE3ZtQEcMrJiKI7+RyGJhF1/Xh6GDNzNjFuzdCO+URC2H0kNAmAq4gwY5iuGEmJVtARctAW4w16rCnMMDlAaUD0S7pdrJUt2dKstBhETSiKuZKR+gMPIux8rss3ZAS2xE3nBPgAZ1SdVNixL7FyJD9bLQPLfOx0ZLeV4VAMBSVaqwgE3SCVzD+ySNY8ZLWbWdSFLE5CY49lfnilN5ZAkW6onkvo/KNzViQ1VO1eagGK4fYfQHMQ48btnrIpEFIIU65/N03hSXdfzeFFvsexjxyURrUgo04w== 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 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 CPU= 0'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 believe a dmb(ishst) is sufficient to ensure that the new PTE writes are visible to other CPUs. I=E2=80=99m not quite sure why the current flush code uses d= sb(ish); it seems like overkill. Thanks Barry