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 2F962C43334 for ; Tue, 21 Jun 2022 05:34:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=j/aD1sUyDz4s8P5cJrkR7XAxC9k3ZxQRTb431j+svLE=; b=47wtEOI0wOKIvm f/TYPDeAwzrSqNLtwD9pMfzOdxgpAA2xN6kCpkxkSPD1w//gxKkJ3OPSdUwTQE4JVecMK8rEMo+9i JGExKgKq53tUGs9zGwSCqA1y7tWkzNMBPLC3mUP7vKI1WmlHwLxBlnXVG3Bljp30GXUOvfmrSSGa4 5xDgZupQ9Be32G7jJ9q9bdqkT6t0SDp3AYc+EfirrirKcuEaFEQRRc+Yrg0yFHYA31DwsM1Cwg0dx R/IgEcvS4sg3sX6M5gm2OZH4/NyR3EVLPoY2OpYoiIVHAuZ3ZKBhtHZ5ydnOT393NBlvW3weuppGh JnaaDpkWnw6/Rd2UNR+A==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1o3WWF-003i1O-4A; Tue, 21 Jun 2022 05:33:43 +0000 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1o3WW6-003hzD-Fb for linux-arm-kernel@lists.infradead.org; Tue, 21 Jun 2022 05:33:38 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1655789610; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=h+MrydMOJRPtRlmLWVZnu2Vf2FmC8y0u+vnzj78C7Ng=; b=SVFER4kxi2YZefPiemDFBaglr9G/muqUPfloaQJnukxy2EXLuPkDsfbSmWHaNYXf6MbiUI 5GdvCtZKsr2BisUqSYXEep+ZG8alhLlnSUHRH2jLwyWdwRePbTh4hc4abwSubyBAP2NBOA K9CTXOjRimIk0TrA+sh4tPn9SCVyFQ8= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-154-pyhe4RwjNv-T_j2ChAXYbA-1; Tue, 21 Jun 2022 01:33:24 -0400 X-MC-Unique: pyhe4RwjNv-T_j2ChAXYbA-1 Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.rdu2.redhat.com [10.11.54.9]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id C9735101AA47; Tue, 21 Jun 2022 05:33:23 +0000 (UTC) Received: from localhost (ovpn-12-183.pek2.redhat.com [10.72.12.183]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 303CF492C3B; Tue, 21 Jun 2022 05:33:21 +0000 (UTC) Date: Tue, 21 Jun 2022 13:33:17 +0800 From: Baoquan He To: Zhen Lei , Catalin Marinas , Ard Biesheuvel Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, "H . Peter Anvin" , Eric Biederman , Rob Herring , Frank Rowand , devicetree@vger.kernel.org, Dave Young , Vivek Goyal , kexec@lists.infradead.org, linux-kernel@vger.kernel.org, Will Deacon , linux-arm-kernel@lists.infradead.org, Jonathan Corbet , linux-doc@vger.kernel.org, Randy Dunlap , Feng Zhou , Kefeng Wang , Chen Zhou , John Donnelly , Dave Kleikamp Subject: Re: [PATCH 5/5] arm64: kdump: Don't defer the reservation of crash high memory Message-ID: References: <20220613080932.663-1-thunder.leizhen@huawei.com> <20220613080932.663-6-thunder.leizhen@huawei.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20220613080932.663-6-thunder.leizhen@huawei.com> X-Scanned-By: MIMEDefang 2.85 on 10.11.54.9 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220620_223334_808072_464EF992 X-CRM114-Status: GOOD ( 41.20 ) 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: , 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 Hi, On 06/13/22 at 04:09pm, Zhen Lei wrote: > If the crashkernel has both high memory above DMA zones and low memory > in DMA zones, kexec always loads the content such as Image and dtb to the > high memory instead of the low memory. This means that only high memory > requires write protection based on page-level mapping. The allocation of > high memory does not depend on the DMA boundary. So we can reserve the > high memory first even if the crashkernel reservation is deferred. > > This means that the block mapping can still be performed on other kernel > linear address spaces, the TLB miss rate can be reduced and the system > performance will be improved. Ugh, this looks a little ugly, honestly. If that's for sure arm64 can't split large page mapping of linear region, this patch is one way to optimize linear mapping. Given kdump setting is necessary on arm64 server, the booting speed is truly impacted heavily. However, I would suggest letting it as is with below reasons: 1) The code will complicate the crashkernel reservatoin code which is already difficult to understand. 2) It can only optimize the two cases, first is CONFIG_ZONE_DMA|DMA32 disabled, the other is crashkernel=,high is specified. While both two cases are corner case, most of systems have CONFIG_ZONE_DMA|DMA32 enabled, and most of systems have crashkernel=xM which is enough. Having them optimized won't bring benefit to most of systems. 3) Besides, the crashkernel=,high can be handled earlier because arm64 alwasys have memblock.bottom_up == false currently, thus we don't need worry arbout the lower limit of crashkernel,high reservation for now. If memblock.bottom_up is set true in the future, this patch doesn't work any more. ... crash_base = memblock_phys_alloc_range(crash_size, CRASH_ALIGN, crash_base, crash_max); So, in my opinion, we can leave the current NON_BLOCK|SECT mapping as is caused by crashkernel reserving, since no regression is brought. And meantime, turning to check if there's any way to make the contiguous linear mapping and later splitting work. The patch 4, 5 in this patchset doesn't make much sense to me, frankly speaking. Thanks Baoquan > > Signed-off-by: Zhen Lei > --- > arch/arm64/mm/init.c | 71 ++++++++++++++++++++++++++++++++++++++++---- > 1 file changed, 65 insertions(+), 6 deletions(-) > > diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c > index fb24efbc46f5ef4..ae0bae2cafe6ab0 100644 > --- a/arch/arm64/mm/init.c > +++ b/arch/arm64/mm/init.c > @@ -141,15 +141,44 @@ static void __init reserve_crashkernel(int dma_state) > unsigned long long crash_max = CRASH_ADDR_LOW_MAX; > char *cmdline = boot_command_line; > int dma_enabled = IS_ENABLED(CONFIG_ZONE_DMA) || IS_ENABLED(CONFIG_ZONE_DMA32); > - int ret; > + int ret, skip_res = 0, skip_low_res = 0; > bool fixed_base; > > if (!IS_ENABLED(CONFIG_KEXEC_CORE)) > return; > > - if ((!dma_enabled && (dma_state != DMA_PHYS_LIMIT_UNKNOWN)) || > - (dma_enabled && (dma_state != DMA_PHYS_LIMIT_KNOWN))) > - return; > + /* > + * In the following table: > + * X,high means crashkernel=X,high > + * unknown means dma_state = DMA_PHYS_LIMIT_UNKNOWN > + * known means dma_state = DMA_PHYS_LIMIT_KNOWN > + * > + * The first two columns indicate the status, and the last two > + * columns indicate the phase in which crash high or low memory > + * needs to be reserved. > + * --------------------------------------------------- > + * | DMA enabled | X,high used | unknown | known | > + * --------------------------------------------------- > + * | N N | low | NOP | > + * | Y N | NOP | low | > + * | N Y | high/low | NOP | > + * | Y Y | high | low | > + * --------------------------------------------------- > + * > + * But in this function, the crash high memory allocation of > + * crashkernel=Y,high and the crash low memory allocation of > + * crashkernel=X[@offset] for crashk_res are mixed at one place. > + * So the table above need to be adjusted as below: > + * --------------------------------------------------- > + * | DMA enabled | X,high used | unknown | known | > + * --------------------------------------------------- > + * | N N | res | NOP | > + * | Y N | NOP | res | > + * | N Y |res/low_res| NOP | > + * | Y Y | res | low_res | > + * --------------------------------------------------- > + * > + */ > > /* crashkernel=X[@offset] */ > ret = parse_crashkernel(cmdline, memblock_phys_mem_size(), > @@ -169,10 +198,33 @@ static void __init reserve_crashkernel(int dma_state) > else if (ret) > return; > > + /* See the third row of the second table above, NOP */ > + if (!dma_enabled && (dma_state == DMA_PHYS_LIMIT_KNOWN)) > + return; > + > + /* See the fourth row of the second table above */ > + if (dma_enabled) { > + if (dma_state == DMA_PHYS_LIMIT_UNKNOWN) > + skip_low_res = 1; > + else > + skip_res = 1; > + } > + > crash_max = CRASH_ADDR_HIGH_MAX; > } else if (ret || !crash_size) { > /* The specified value is invalid */ > return; > + } else { > + /* See the 1-2 rows of the second table above, NOP */ > + if ((!dma_enabled && (dma_state == DMA_PHYS_LIMIT_KNOWN)) || > + (dma_enabled && (dma_state == DMA_PHYS_LIMIT_UNKNOWN))) > + return; > + } > + > + if (skip_res) { > + crash_base = crashk_res.start; > + crash_size = crashk_res.end - crashk_res.start + 1; > + goto check_low; > } > > fixed_base = !!crash_base; > @@ -202,9 +254,18 @@ static void __init reserve_crashkernel(int dma_state) > return; > } > > + crashk_res.start = crash_base; > + crashk_res.end = crash_base + crash_size - 1; > + > +check_low: > + if (skip_low_res) > + return; > + > if ((crash_base >= CRASH_ADDR_LOW_MAX) && > crash_low_size && reserve_crashkernel_low(crash_low_size)) { > memblock_phys_free(crash_base, crash_size); > + crashk_res.start = 0; > + crashk_res.end = 0; > return; > } > > @@ -219,8 +280,6 @@ static void __init reserve_crashkernel(int dma_state) > if (crashk_low_res.end) > kmemleak_ignore_phys(crashk_low_res.start); > > - crashk_res.start = crash_base; > - crashk_res.end = crash_base + crash_size - 1; > insert_resource(&iomem_resource, &crashk_res); > } > > -- > 2.25.1 > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel