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AJvYcCUBH9erp68NrqWnNhUXw3yVzQgF6USIByWUiMh0RaZMq2JsuO8MxjqhptBxfNeSihoCEkCWAsvb2RHSmZ9bdjyFeZ4= X-Gm-Message-State: AOJu0Yy1ebbGUmR6K5DBbB5dx7am59t6BWSg6/63P7/rthpS2V+DmqGr ek6ovq2VlR5t54VMOI/tbPCjay6iqBdJm/9/mK2foKG/oeVBw/s2TNjgVZCrRM4pFHaHy8YkdfZ GULPGZLsxxv0Byu+vP3TQwfCHwtl/rCNXGFxsRg== X-Google-Smtp-Source: AGHT+IGIN9RjvMLUDIpAmm7RsOi7H4k0RkSaVfgiFkKRBh0h1VzmfcxUfv/UOTCfGZuR0DO8KsX58y/fWkIBiXxYREE= X-Received: by 2002:a81:7785:0:b0:615:1dc6:429a with SMTP id s127-20020a817785000000b006151dc6429amr922136ywc.46.1712189564372; Wed, 03 Apr 2024 17:12:44 -0700 (PDT) MIME-Version: 1.0 References: <20240402051154.476244-1-rmclure@linux.ibm.com> <20240402051154.476244-11-rmclure@linux.ibm.com> In-Reply-To: <20240402051154.476244-11-rmclure@linux.ibm.com> From: Pasha Tatashin Date: Wed, 3 Apr 2024 20:12:07 -0400 Message-ID: Subject: Re: [PATCH v12 10/11] powerpc: mm: Use set_pte_at_unchecked() for early-boot / internal usages To: Rohan McLure Cc: linuxppc-dev@lists.ozlabs.org, mpe@ellerman.id.au, christophe.leroy@csgroup.eu, linux-mm@kvack.org, linux-riscv@lists.infradead.org, linux-arm-kernel@lists.infradead.org, x86@kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 5EDC6100002 X-Stat-Signature: hp87qemk1zaf5x8q6kf3hp17n7izdnhc X-HE-Tag: 1712189565-147999 X-HE-Meta: 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 G+pArR0K 91nUrs+8991f/2Qow8RV2IdB5hmOyAIJy09mobX6+ZpOyMDHFFKs0f0ePalG6S5Z5RIyABUayBErl+5foDGcbidJLchsGU7cxTEqd87zUgujhH/JxlDmMTzmO9uLeMM+iwYpP8JxUF8hqksHMPn/dxG8N+09WXvjfxpTzvySDLYcuvBiP6fUnb1znlN+D/uBNKZg/ECBsLJJ212WOwLM5Wf1EvziErObe7dOF+kyuu4q68POzAvXWbvk29NZXRoDkeGTa9TBD2gNTbIIxQHzkoXHvGb1juM67BSx7GbLhra7lhaKx/vgY9M7nrswJ/uQEz0v4qu4aUCatAr0ukOZFZjeSLtpFp/QWcJkM X-Bogosity: Ham, tests=bogofilter, spamicity=0.005480, 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 Tue, Apr 2, 2024 at 1:13=E2=80=AFAM Rohan McLure = wrote: > > In the new set_ptes() API, set_pte_at() (a special case of set_ptes()) > is intended to be instrumented by the page table check facility. There > are however several other routines that constitute the API for setting > page table entries, including set_pmd_at() among others. Such routines > are themselves implemented in terms of set_ptes_at(). > > A future patch providing support for page table checking on powerpc > must take care to avoid duplicate calls to > page_table_check_p{te,md,ud}_set(). Allow for assignment of pte entries > without instrumentation through the set_pte_at_unchecked() routine > introduced in this patch. > > Cause API-facing routines that call set_pte_at() to instead call > set_pte_at_unchecked(), which will remain uninstrumented by page > table check. set_ptes() is itself implemented by calls to > __set_pte_at(), so this eliminates redundant code. > > Also prefer set_pte_at_unchecked() in early-boot usages which should not = be > instrumented. Would not the early-boot usage be all kernel mappings that are ignored by page table check anways? Sounds like it is better to only use the set_pte_at_unchecked() version where it is really needed, which is to avoid double counting. This will keep the usage of this function only for one purpose that is easy to follow. Pasha