From patchwork Wed Mar 19 15:05:34 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Miko=C5=82aj_Lenczewski?= X-Patchwork-Id: 14022770 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 CE8B7C35FFA for ; Wed, 19 Mar 2025 15:13:06 +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: Content-Type:MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:Cc: To:From:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=Vhd9OLP19nHpcre+78tpM1P6tFgF3pG7vpM2folBU5Q=; b=iTbn5nDVUUXXp8Pjk4swMpd5Ho haii0auaF8xV6M8qbFAiA1rYfdM7t4hUo+0MQbvoUPvBgR0w3g67NUqvKxbi+vh3C1ogBNqG+9yYV aT5vmFIQmyR/fPTkSLB+6vS1ppB6rtzKQcOC5FtsyxAd+nn0q9o5fYn7/xfLhubsURfGch/7+5R1b DpImwzJe/42iyemH58J3wkBs9mqj/iTH1qFZEp8NmQV1qB59ZvI14RGgSeS+i5jimXzKLrHy6Wiwm KxLWA4qLHyg3chTcMzwm7EZu6jhaNJwBir/gZ3SbrCIBmRvnnzXuvq24hhU1QMM3CKgomyfbTSVSu jGbWq4lw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tuv6G-00000009KsL-1TV8; Wed, 19 Mar 2025 15:12:56 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tuuzm-00000009Jh7-4AOv for linux-arm-kernel@lists.infradead.org; Wed, 19 Mar 2025 15:06:16 +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 CA3051655; Wed, 19 Mar 2025 08:06:22 -0700 (PDT) Received: from mazurka.cambridge.arm.com (mazurka.cambridge.arm.com [10.2.80.18]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id A210E3F694; Wed, 19 Mar 2025 08:06:10 -0700 (PDT) From: =?utf-8?q?Miko=C5=82aj_Lenczewski?= To: ryan.roberts@arm.com, suzuki.poulose@arm.com, yang@os.amperecomputing.com, corbet@lwn.net, catalin.marinas@arm.com, will@kernel.org, jean-philippe@linaro.org, robin.murphy@arm.com, joro@8bytes.org, akpm@linux-foundation.org, ardb@kernel.org, mark.rutland@arm.com, joey.gouly@arm.com, maz@kernel.org, james.morse@arm.com, broonie@kernel.org, oliver.upton@linux.dev, baohua@kernel.org, david@redhat.com, ioworker0@gmail.com, jgg@ziepe.ca, nicolinc@nvidia.com, mshavit@google.com, jsnitsel@redhat.com, smostafa@google.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, iommu@lists.linux.dev Cc: =?utf-8?q?Miko=C5=82aj_Lenczewski?= Subject: [PATCH v4 3/3] arm64/mm: Elide tlbi in contpte_convert() under BBML2 Date: Wed, 19 Mar 2025 15:05:34 +0000 Message-ID: <20250319150533.37440-5-miko.lenczewski@arm.com> X-Mailer: git-send-email 2.48.1 In-Reply-To: <20250319150533.37440-2-miko.lenczewski@arm.com> References: <20250319150533.37440-2-miko.lenczewski@arm.com> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250319_080615_070319_E6FD96B7 X-CRM114-Status: GOOD ( 13.37 ) 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 When converting a region via contpte_convert() to use mTHP, we have two different goals. We have to mark each entry as contiguous, and we would like to smear the dirty and young (access) bits across all entries in the contiguous block. Currently, we do this by first accumulating the dirty and young bits in the block, using an atomic __ptep_get_and_clear() and the relevant pte_{dirty,young}() calls, performing a tlbi, and finally smearing the correct bits across the block using __set_ptes(). This approach works fine for BBM level 0, but with support for BBM level 2 we are allowed to reorder the tlbi to after setting the pagetable entries. We expect the time cost of a tlbi to be much greater than the cost of clearing and resetting the PTEs. As such, this reordering of the tlbi outside the window where our PTEs are invalid greatly reduces the duration the PTE are visibly invalid for other threads. This reduces the likelyhood of a concurrent page walk finding an invalid PTE, reducing the likelyhood of a fault in other threads, and improving performance (more so when there are more threads). Because we support via allowlist only bbml2 implementations that never raise conflict aborts and instead invalidate the tlb entries automatically in hardware, we can avoid the final flush altogether. Avoiding flushes is a win. Signed-off-by: MikoĊ‚aj Lenczewski Reviewed-by: Ryan Roberts --- arch/arm64/mm/contpte.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/arm64/mm/contpte.c b/arch/arm64/mm/contpte.c index 55107d27d3f8..77ed03b30b72 100644 --- a/arch/arm64/mm/contpte.c +++ b/arch/arm64/mm/contpte.c @@ -68,7 +68,8 @@ static void contpte_convert(struct mm_struct *mm, unsigned long addr, pte = pte_mkyoung(pte); } - __flush_tlb_range(&vma, start_addr, addr, PAGE_SIZE, true, 3); + if (!system_supports_bbml2_noabort()) + __flush_tlb_range(&vma, start_addr, addr, PAGE_SIZE, true, 3); __set_ptes(mm, start_addr, start_ptep, pte, CONT_PTES); }