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AFNElJ+QPkjp0d089jo7DaPNMNmyy+FChEchUfohnUXusDMISsR6gOG/zscEcX2n2V8qofTmyfbvyodAVHU1fUPK67A=@vger.kernel.org X-Gm-Message-State: AOJu0Yzvv3HLaH7E9nsaUroJ+20+lyZ4pSUS0OUX87gR0neXH+CjH33Z 64091IizaIYcu8TVFdo8IPfbozlfvaPCiL8ZJ/uf0aGU1VlOrM6hnU9eSD99knfzUDWKuK31uw= = X-Received: from edpg3.prod.google.com ([2002:aa7:d1c3:0:b0:68b:f715:5345]) (user=ardb job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6402:a29b:10b0:683:be46:c20c with SMTP id 4fb4d7f45d1cf-68c8a65763dmr15813a12.16.1780066952419; Fri, 29 May 2026 08:02:32 -0700 (PDT) Date: Fri, 29 May 2026 17:02:03 +0200 In-Reply-To: <20260529150150.1670604-17-ardb+git@google.com> Precedence: bulk X-Mailing-List: linux-hardening@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260529150150.1670604-17-ardb+git@google.com> X-Developer-Key: i=ardb@kernel.org; a=openpgp; fpr=F43D03328115A198C90016883D200E9CA6329909 X-Developer-Signature: v=1; a=openpgp-sha256; l=1322; i=ardb@kernel.org; h=from:subject; bh=4saoJOhT3cEc7dpWXJZksxFCf7gWJDz5CDZcsy0RHE0=; b=owGbwMvMwCVmkMcZplerG8N4Wi2JIUtyVe4Vpn2a3EuL7z5c9yPshq/FTf8NSmKzXz68s33ZB ld1mYh7HaUsDGJcDLJiiiwCs/++23l6olSt8yxZmDmsTCBDGLg4BWAibDIM/2u5Yv7kFfP5v2Ww OfqOx3NBpOKey7t5vhR6LI5Y9SY78z3D/5SO1Jh354yPPvIQfsjEWFAfIL3vxawn2VI8ya8XJ21 dxwwA X-Mailer: git-send-email 2.54.0.823.g6e5bcc1fc9-goog Message-ID: <20260529150150.1670604-29-ardb+git@google.com> Subject: [PATCH v7 12/15] sh: Drop cache flush of the zero page at boot From: Ard Biesheuvel To: linux-arm-kernel@lists.infradead.org Cc: linux-kernel@vger.kernel.org, will@kernel.org, catalin.marinas@arm.com, mark.rutland@arm.com, Ard Biesheuvel , Ryan Roberts , Anshuman Khandual , Kevin Brodsky , Liz Prucka , Seth Jenkins , Kees Cook , Mike Rapoport , David Hildenbrand , Andrew Morton , Jann Horn , linux-mm@kvack.org, linux-hardening@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-sh@vger.kernel.org, Yoshinori Sato , Rich Felker , John Paul Adrian Glaubitz , Geert Uytterhoeven Content-Type: text/plain; charset="UTF-8" From: Ard Biesheuvel SuperH performs cache maintenance on the zero page during boot, presumably because before commit 6215d9f4470f ("arch, mm: consolidate empty_zero_page") the zero page did double duty as a boot params region, and was cleared separately, as it was not part of BSS. The memset() in question was dropped by that commit, but the __flush_wback_region() call remained. As empty_zero_page[] has been moved to BSS, it can be treated as any other BSS memory, and so the cache flush can be dropped. Cc: Yoshinori Sato Cc: Rich Felker Cc: John Paul Adrian Glaubitz Cc: Mike Rapoport Cc: Geert Uytterhoeven Signed-off-by: Ard Biesheuvel --- arch/sh/mm/init.c | 3 --- 1 file changed, 3 deletions(-) diff --git a/arch/sh/mm/init.c b/arch/sh/mm/init.c index 4e40d5e96be9..110308bdef01 100644 --- a/arch/sh/mm/init.c +++ b/arch/sh/mm/init.c @@ -331,9 +331,6 @@ void __init mem_init(void) /* Set this up early, so we can take care of the zero page */ cpu_cache_init(); - /* clear the zero-page */ - __flush_wback_region(empty_zero_page, PAGE_SIZE); - vsyscall_init(); pr_info("virtual kernel memory layout:\n" -- 2.54.0.823.g6e5bcc1fc9-goog