From patchwork Fri Apr 7 01:15:05 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Baoquan He X-Patchwork-Id: 13204368 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 47A00C761A6 for ; Fri, 7 Apr 2023 01:16:31 +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: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=244VF1KaesQ9rtP4sIODNU8vztkIGN7fhYyahJHKuKw=; b=yt3NXh0XdrNFdR CENXLSqqhcAjhbtbsWc311TvLs2kt9WMuNjch59XXuA61W0a4b+SXdStPeEjNBd66j0gw17ALiEI7 I7MBW6jQruf+crtxg4I0UwzN2jxMheWJhN+72Pw7cxZBkYRqQZxB/F/FHTd4lBr9QA8sn8bFm6wBs 2ura0uI7owb73ZUmY4+t1RoX0naEgb8whk2sPHPcifpHY5WfMKiJOTCKFOR3ZNl5dFw7jAT7r/z1G WEOm764Ir4bSAIOy9MhbxlOYFTaEvu4sbkrXQB5ylRirywZjDC9ieD609KpNH6DlRlHsdStFx1VLs nPRBoHfZ3L8edCKt6fjQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1pkahO-008vqy-2y; Fri, 07 Apr 2023 01:15:30 +0000 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by bombadil.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1pkahK-008vpV-2V for linux-arm-kernel@lists.infradead.org; Fri, 07 Apr 2023 01:15:28 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1680830125; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Oy29AYYgML7Ch0hXumRCRb+rrtZVQXUDb4HMadFEibw=; b=Dqxhov5hLslDqhp212FJ7hFxgOQ3+UP4OmzNKqKtevO5957Q340eMZFOFkS8o96z0pboOP lXJkUSHeTRyDrVvZtWJ6pK7isaT3QUhSIbeuFkaRr8Nsyl9Bb3VN61M+h9A776k0ttL0ki +TYWm5+8cYBqORLGhvb/XXJUDqmoQSE= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-624-lIi9gKHuOBqBB7clS_i7ww-1; Thu, 06 Apr 2023 21:15:24 -0400 X-MC-Unique: lIi9gKHuOBqBB7clS_i7ww-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 180203806737; Fri, 7 Apr 2023 01:15:24 +0000 (UTC) Received: from MiWiFi-R3L-srv.redhat.com (ovpn-12-86.pek2.redhat.com [10.72.12.86]) by smtp.corp.redhat.com (Postfix) with ESMTP id E509718EC6; Fri, 7 Apr 2023 01:15:17 +0000 (UTC) From: Baoquan He To: linux-kernel@vger.kernel.org Cc: catalin.marinas@arm.com, rppt@kernel.org, thunder.leizhen@huawei.com, will@kernel.org, ardb@kernel.org, horms@kernel.org, John.p.donnelly@oracle.com, kexec@lists.infradead.org, linux-arm-kernel@lists.infradead.org, Baoquan He Subject: [PATCH v2 1/3] arm64: kdump : take off the protection on crashkernel memory region Date: Fri, 7 Apr 2023 09:15:05 +0800 Message-Id: <20230407011507.17572-2-bhe@redhat.com> In-Reply-To: <20230407011507.17572-1-bhe@redhat.com> References: <20230407011507.17572-1-bhe@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.5 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230406_181526_891369_6C1297D3 X-CRM114-Status: GOOD ( 15.12 ) 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 Problem: ======= On arm64, block and section mapping is supported to build page tables. However, currently it enforces to take base page mapping for the whole linear mapping if CONFIG_ZONE_DMA or CONFIG_ZONE_DMA32 is enabled and crashkernel kernel parameter is set. This will cause longer time of the linear mapping process during bootup and severe performance degradation during running time. Root cause: ========== On arm64, crashkernel reservation relies on knowing the upper limit of low memory zone because it needs to reserve memory in the zone so that devices' DMA addressing in kdump kernel can be satisfied. However, the upper limit of low memory on arm64 is variant. And the upper limit can only be decided late till bootmem_init() is called [1]. And we need to map the crashkernel region with base page granularity when doing linear mapping, because kdump needs to protect the crashkernel region via set_memory_valid(,0) after kdump kernel loading. However, arm64 doesn't support well on splitting the built block or section mapping due to some cpu reststriction [2]. And unfortunately, the linear mapping is done before bootmem_init(). To resolve the above conflict on arm64, the compromise is enforcing to take base page mapping for the entire linear mapping if crashkernel is set, and CONFIG_ZONE_DMA or CONFIG_ZONE_DMA32 is enabed. Hence performance is sacrificed. Solution: ========= Comparing with the base page mapping for the whole linear region, it's better to take off the protection on crashkernel memory region for the time being because the anticipated stamping on crashkernel memory region could only happen in a chance in one million, while the base page mapping for the whole linear region is mitigating arm64 systems with crashkernel set always. [1] https://lore.kernel.org/all/YrIIJkhKWSuAqkCx@arm.com/T/#u [2] https://lore.kernel.org/linux-arm-kernel/20190911182546.17094-1-nsaenzjulienne@suse.de/T/ Signed-off-by: Baoquan He Acked-by: Catalin Marinas Acked-by: Mike Rapoport (IBM) Reviewed-by: Zhen Lei --- arch/arm64/include/asm/kexec.h | 6 ------ arch/arm64/kernel/machine_kexec.c | 20 -------------------- 2 files changed, 26 deletions(-) diff --git a/arch/arm64/include/asm/kexec.h b/arch/arm64/include/asm/kexec.h index 559bfae26715..9ac9572a3bbe 100644 --- a/arch/arm64/include/asm/kexec.h +++ b/arch/arm64/include/asm/kexec.h @@ -102,12 +102,6 @@ void cpu_soft_restart(unsigned long el2_switch, unsigned long entry, int machine_kexec_post_load(struct kimage *image); #define machine_kexec_post_load machine_kexec_post_load - -void arch_kexec_protect_crashkres(void); -#define arch_kexec_protect_crashkres arch_kexec_protect_crashkres - -void arch_kexec_unprotect_crashkres(void); -#define arch_kexec_unprotect_crashkres arch_kexec_unprotect_crashkres #endif #define ARCH_HAS_KIMAGE_ARCH diff --git a/arch/arm64/kernel/machine_kexec.c b/arch/arm64/kernel/machine_kexec.c index ce3d40120f72..22da7fc1ff50 100644 --- a/arch/arm64/kernel/machine_kexec.c +++ b/arch/arm64/kernel/machine_kexec.c @@ -268,26 +268,6 @@ void machine_crash_shutdown(struct pt_regs *regs) pr_info("Starting crashdump kernel...\n"); } -void arch_kexec_protect_crashkres(void) -{ - int i; - - for (i = 0; i < kexec_crash_image->nr_segments; i++) - set_memory_valid( - __phys_to_virt(kexec_crash_image->segment[i].mem), - kexec_crash_image->segment[i].memsz >> PAGE_SHIFT, 0); -} - -void arch_kexec_unprotect_crashkres(void) -{ - int i; - - for (i = 0; i < kexec_crash_image->nr_segments; i++) - set_memory_valid( - __phys_to_virt(kexec_crash_image->segment[i].mem), - kexec_crash_image->segment[i].memsz >> PAGE_SHIFT, 1); -} - #ifdef CONFIG_HIBERNATION /* * To preserve the crash dump kernel image, the relevant memory segments