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 X-Spam-Level: X-Spam-Status: No, score=-17.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 46561C4361B for ; Tue, 15 Dec 2020 15:30:46 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 04974224B8 for ; Tue, 15 Dec 2020 15:30:45 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 04974224B8 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:MIME-Version:Message-Id:Date:Subject:To:From: Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender :Resent-To:Resent-Cc:Resent-Message-ID:In-Reply-To:References:List-Owner; bh=7Fh3eJ/0SkOH2DAABi5yx8GhTa/johM0mGooNLbxxm0=; b=BUsAqg1Eif83NMP8wzDzC8GzAX 4bVP5VSimMP9ef924N+S+jOSDi313LkoRN7wCMIGklOH7E5BN7EumyCaE8G2JmjO7KrePUUNKIQvH vfZEA6aOf8XMkP6LIbcT4+sB2JU6kd7v3q+nj1ProPs4Ub5lMFyLAAgwlAKSAaqpT4CoewZQrYc6I wJxG5aceaRLGOQUPb6X6KI+naOP2lCBwICWK13sdpRKn1fA6jXd4UBVzJSSpgkWjNRdWrRTY2FxWo 1n6hGUr1qIc1JuMjSS03rCXXzK3QbagNYpBi6t5IeFbD+hzih7+3NDrdPNxbef4fkoApEbtSI37ib cQohbKaA==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kpCGd-00075F-7n; Tue, 15 Dec 2020 15:29:35 +0000 Received: from mail.kernel.org ([198.145.29.99]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1kpCGZ-00074O-9T for linux-arm-kernel@lists.infradead.org; Tue, 15 Dec 2020 15:29:34 +0000 Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 43EA0224B8; Tue, 15 Dec 2020 15:29:30 +0000 (UTC) Received: from 78.163-31-62.static.virginmediabusiness.co.uk ([62.31.163.78] helo=why.lan) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94) (envelope-from ) id 1kpCGW-001WO1-4f; Tue, 15 Dec 2020 15:29:28 +0000 From: Marc Zyngier To: linux-arm-kernel@lists.infradead.org Subject: [PATCH] arm64: Warn the user when a small VA_BITS value wastes memory Date: Tue, 15 Dec 2020 15:29:18 +0000 Message-Id: <20201215152918.1511108-1-maz@kernel.org> X-Mailer: git-send-email 2.29.2 MIME-Version: 1.0 X-SA-Exim-Connect-IP: 62.31.163.78 X-SA-Exim-Rcpt-To: linux-arm-kernel@lists.infradead.org, catalin.marinas@arm.com, will@kernel.org, ardb@kernel.org, mark.rutland@arm.com, qperret@google.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201215_102931_393757_195078BE X-CRM114-Status: GOOD ( 17.50 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , Catalin Marinas , Will Deacon , Ard Biesheuvel , qperret@google.com Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org The memblock code ignores any memory that doesn't fit in the linear mapping. In order to preserve the distance between two physical memory locations and their mappings in the linear map, any hole between two memory regions occupies the same space in the linear map. On most systems, this is hardly a problem (the memory banks are close together, and VA_BITS represents a large space compared to the available memory *and* the potential gaps). On NUMA systems, things are quite different: the gaps between the memory nodes can be pretty large compared to the memory size itself, and the range from memblock_start_of_DRAM() to memblock_end_of_DRAM() can exceed the space described by VA_BITS. Unfortunately, we're not very good at making this obvious to the user, and on a D05 system (two sockets and 4 nodes with 64GB each) accidentally configured with 39bit VA, we display something like this: [ 0.000000] NUMA: NODE_DATA [mem 0x1ffbffe100-0x1ffbffffff] [ 0.000000] NUMA: NODE_DATA [mem 0x2febfc1100-0x2febfc2fff] [ 0.000000] NUMA: Initmem setup node 2 [] [ 0.000000] NUMA: NODE_DATA [mem 0x2febfbf200-0x2febfc10ff] [ 0.000000] NUMA: NODE_DATA(2) on node 1 [ 0.000000] NUMA: Initmem setup node 3 [] [ 0.000000] NUMA: NODE_DATA [mem 0x2febfbd300-0x2febfbf1ff] [ 0.000000] NUMA: NODE_DATA(3) on node 1 which isn't very explicit, and doesn't tell the user why 128GB have suddently disappeared. Let's add a warning message telling the user that memory has been truncated, and offer a potential solution (bumping VA_BITS up). Signed-off-by: Marc Zyngier --- arch/arm64/mm/init.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c index 095540667f0f..cd5da059de85 100644 --- a/arch/arm64/mm/init.c +++ b/arch/arm64/mm/init.c @@ -283,6 +283,9 @@ void __init arm64_memblock_init(void) memstart_addr = round_down(memblock_start_of_DRAM(), ARM64_MEMSTART_ALIGN); + if ((memblock_end_of_DRAM() - memstart_addr) > linear_region_size) + pr_warn("Memory doesn't fit in the linear mapping, VA_BITS too small\n"); + /* * Remove the memory that we will not be able to cover with the * linear mapping. Take care not to clip the kernel which may be -- 2.29.2 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel