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b=FYw9u4JyY6IrjZ+viPaZhpv445h12H08bmsKim9gDxQEEoQBx1U/lWp+6b2wsU7VY /J2vJyAfpJTNB1U+Fu66WudIsqY6Pu51sgPNtYLjNThG4MhY4d0cmCh8PGbhTAliE7 hIezCvoesoIVE6+xRk5gSX8tCRdr7ESRj92vazq8WMApe20OPqUZkj367zixcGYMrg iXcwnX33D7XigvEo5XXl7wzg6mtV3bD/FFmz2q/Qfd9mjZ5b9zJsUIOxZI+gjguYJF /wdgME4lFkmzdiT4CSFba0bE78J276XhXpsTTKJ6Uu/5Hz/cSHcfASvav0Ov6OoqNG 2IyKmtuqiDysA== From: SeongJae Park To: Anshuman Khandual Cc: SeongJae Park , linux-mm@kvack.org, Andrew Morton , David Hildenbrand , Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Namhyung Kim , linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] perf/events: Replace READ_ONCE() with standard pgtable accessors Date: Sat, 28 Feb 2026 08:49:58 -0800 Message-ID: <20260228164959.39672-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260227062744.2215491-1-anshuman.khandual@arm.com> References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: BA7AB120005 X-Stat-Signature: 9xxfjf1istpwq1ete6pu1dn4z9h7tyfg X-Rspam-User: X-HE-Tag: 1772297408-530028 X-HE-Meta: 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 5voDhK/m c30N8ZE/C8CPdLaET1Bi9G09M9u9bPhzCG1exJzqL8xunLME= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, 27 Feb 2026 06:27:44 +0000 Anshuman Khandual wrote: > Replace raw READ_ONCE() dereferences of pgtable entries with corresponding > standard page table accessors pxdp_get() in perf_get_pgtable_size(). These > accessors default to READ_ONCE() on platforms that don't override them. So > there is no functional change on such platforms. > > However arm64 platform is being extended to support 128 bit page tables via > a new architecture feature i.e FEAT_D128 in which case READ_ONCE() will not > provide required single copy atomic access for 128 bit page table entries. > Although pxdp_get() accessors can later be overridden on arm64 platform to > extend required single copy atomicity support on 128 bit entries. > > Cc: Andrew Morton > Cc: David Hildenbrand > Cc: Peter Zijlstra > Cc: Ingo Molnar > Cc: Arnaldo Carvalho de Melo > Cc: Namhyung Kim > Cc: linux-perf-users@vger.kernel.org > Cc: linux-mm@kvack.org > Cc: linux-kernel@vger.kernel.org > Acked-by: Peter Zijlstra (Intel) > Signed-off-by: Anshuman Khandual Acked-by: SeongJae Park Thanks, SJ [...]