From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id CAF2ECCFA05 for ; Thu, 6 Nov 2025 16:10:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From: Reply-To:Content-Type:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=q/CYVWkdDZGtRQRhFehi9aOOX3xvbt9P8Z4jUxH40cI=; b=nPfwdEe+bS2yPpi9XLcirk+CU5 sK20DdYjbp2MWysIxj2VJBfhACNWAA+wyAP5GLxmgCD4MBUh86KdbOiirQiCGh0bB7hzcyiQKlClI XlxYhhdpydHbQF9sQVQsS9GZghCfpMpvU8SUmtMS19KNm812C3NVXx+fq2Dm7fODDAiLHFoqN2G3g T5zheDEqZGReaOK+v9OKn2uPMbTSTkdvHXLeSkQny8G+E6ERJmTBniLrk4W8PMdmMwLn1H78hHQpZ 94QmObKsu82RTyHmGT18GS5d1jnpsmsZd25WMDjiJ/R1KhfjrRxRr+Ak3WJYeN2UOT/Wqmw1ZzDnV RaMmz9ow==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vH2Yk-0000000Fsnq-2Hlg; Thu, 06 Nov 2025 16:10:02 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vH2Yh-0000000Fsl4-2l6t for linux-arm-kernel@lists.infradead.org; Thu, 06 Nov 2025 16:10:00 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 26FE3169C; Thu, 6 Nov 2025 08:09:51 -0800 (PST) Received: from e125769.cambridge.arm.com (e125769.cambridge.arm.com [10.1.196.27]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 8B1433F66E; Thu, 6 Nov 2025 08:09:57 -0800 (PST) From: Ryan Roberts To: catalin.marinas@arm.com, will@kernel.org, yang@os.amperecomputing.com, david@redhat.com, ardb@kernel.org, dev.jain@arm.com, scott@os.amperecomputing.com, cl@gentwo.org Cc: Ryan Roberts , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: [PATCH v2 2/3] arm64: mm: Optimize range_split_to_ptes() Date: Thu, 6 Nov 2025 16:09:42 +0000 Message-ID: <20251106160945.3182799-3-ryan.roberts@arm.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20251106160945.3182799-1-ryan.roberts@arm.com> References: <20251106160945.3182799-1-ryan.roberts@arm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20251106_080959_740285_F29BA22C X-CRM114-Status: GOOD ( 13.21 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Enter lazy_mmu mode while splitting a range of memory to pte mappings. This causes barriers, which would otherwise be emitted after every pte (and pmd/pud) write, to be deferred until exiting lazy_mmu mode. For large systems, this is expected to significantly speed up fallback to pte-mapping the linear map for the case where the boot CPU has BBML2_NOABORT, but secondary CPUs do not. I haven't directly measured it, but this is equivalent to commit 1fcb7cea8a5f ("arm64: mm: Batch dsb and isb when populating pgtables"). Note that for the path from arch_kfence_init_pool(), we may sleep while allocating memory inside the lazy_mmu mode. Sleeping is not allowed by generic code inside lazy_mmu, but we know that the arm64 implementation is sleep-safe. So this is ok and follows the same pattern already used by split_kernel_leaf_mapping(). Signed-off-by: Ryan Roberts --- arch/arm64/mm/mmu.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c index a364ac2c9c61..652bb8c14035 100644 --- a/arch/arm64/mm/mmu.c +++ b/arch/arm64/mm/mmu.c @@ -832,8 +832,14 @@ static const struct mm_walk_ops split_to_ptes_ops = { static int range_split_to_ptes(unsigned long start, unsigned long end, gfp_t gfp) { - return walk_kernel_page_table_range_lockless(start, end, + int ret; + + arch_enter_lazy_mmu_mode(); + ret = walk_kernel_page_table_range_lockless(start, end, &split_to_ptes_ops, NULL, &gfp); + arch_leave_lazy_mmu_mode(); + + return ret; } static bool linear_map_requires_bbml2 __initdata; -- 2.43.0