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=-14.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT autolearn=unavailable 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 39D9AC432C0 for ; Fri, 29 Nov 2019 19:59:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0ECDB2176D for ; Fri, 29 Nov 2019 19:59:42 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="YXkmupl3" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727133AbfK2T7m (ORCPT ); Fri, 29 Nov 2019 14:59:42 -0500 Received: from us-smtp-2.mimecast.com ([205.139.110.61]:54053 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727107AbfK2T7l (ORCPT ); Fri, 29 Nov 2019 14:59:41 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1575057580; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=/y8p7TWJ4+9dx0qZYntYI0vqqca78jHSFlqFEn+6Y9I=; b=YXkmupl3b6m/6g7V0RJKTlWyd3F3cWO5v4Z+4hft9LbjXJqGpxyDYIcTUw19KTCzUZBbQX 9gTwJG5dlKSZ27iBWXQ20wwAyvnhA0gtWU4BNVGprkuBH5h4mEEBh4d2co3zoga1xxll1z 3ee7Pd90ZJ/0evvupakme6jFkh6sMU8= Received: from mail-pf1-f199.google.com (mail-pf1-f199.google.com [209.85.210.199]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-336-OSpe2VMAMbqDnecsklNsWA-1; Fri, 29 Nov 2019 14:59:38 -0500 Received: by mail-pf1-f199.google.com with SMTP id b17so18586118pfb.8 for ; Fri, 29 Nov 2019 11:59:37 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references; bh=D7Q1sNAJK7KGCeC1/osi4u/yd8LMbojW2DcAg7eyhwk=; b=tUWxtv/4woHH1PCIgbXqOYIxgqOYrKa+1OSHoDJdQScYgDcgS+WxuX5ZunYCxXmHeu saWukriU41IGqIdiMX9mVGz55qP0u6XutEyFecKNLvpbyLei4GUkH4yqNWaMw+2RMFsa eK23n6Sm9aIirQG5R33mxILkeh3WaW29u2XCxMSAwvdpNyyJazquNngLyPyNSP1sUO5D cq/gviHInQV837GXa2W/BIVt8hDetAsSleztE7p/QhkOeJbP1QlRa5ZZqpN6S2sVUr9U EBWe2IshaGWDj15pyetPpobrvW5SJPWjMynSRor4sgWUL5P3LTlqE7hBMe2E/21DYPlH G9BA== X-Gm-Message-State: APjAAAWaJue9ijh3TXCh+UFWV26htzjMzlLcPdCglm/FL8hXV+zlRvlt 1MCx9tqrUlduklq/PuboOvwE7zts7kjIwjFEe1V5Aayy4PRROZx6oAreoZOuY+t5VIs58JggikW J47oPFgX3hBGlw31KH7NTuXgu X-Received: by 2002:a63:6f4c:: with SMTP id k73mr15574206pgc.374.1575057575545; Fri, 29 Nov 2019 11:59:35 -0800 (PST) X-Google-Smtp-Source: APXvYqxxfC5l5m0YoqdbJOwab9vDMWknIRaUJM6sjnSau+oJsA046vHWiBYg3wYv5hDxMjiI/P8T+w== X-Received: by 2002:a63:6f4c:: with SMTP id k73mr15574178pgc.374.1575057575265; Fri, 29 Nov 2019 11:59:35 -0800 (PST) Received: from localhost ([122.177.85.74]) by smtp.gmail.com with ESMTPSA id r28sm23294033pgk.75.2019.11.29.11.59.33 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 29 Nov 2019 11:59:34 -0800 (PST) From: Bhupesh Sharma To: linux-kernel@vger.kernel.org Cc: bhsharma@redhat.com, bhupesh.linux@gmail.com, x86@kernel.org, linuxppc-dev@lists.ozlabs.org, linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, kexec@lists.infradead.org, Boris Petkov , Ingo Molnar , Thomas Gleixner , James Morse , Mark Rutland , Will Deacon , Steve Capper , Catalin Marinas , Ard Biesheuvel , Michael Ellerman , Paul Mackerras , Benjamin Herrenschmidt , Dave Anderson , Kazuhito Hagio Subject: [RESEND PATCH v5 1/5] crash_core, vmcoreinfo: Append 'MAX_PHYSMEM_BITS' to vmcoreinfo Date: Sat, 30 Nov 2019 01:29:15 +0530 Message-Id: <1575057559-25496-2-git-send-email-bhsharma@redhat.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1575057559-25496-1-git-send-email-bhsharma@redhat.com> References: <1575057559-25496-1-git-send-email-bhsharma@redhat.com> X-MC-Unique: OSpe2VMAMbqDnecsklNsWA-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Right now user-space tools like 'makedumpfile' and 'crash' need to rely on a best-guess method of determining value of 'MAX_PHYSMEM_BITS' supported by underlying kernel. This value is used in user-space code to calculate the bit-space required to store a section for SPARESMEM (similar to the existing calculation method used in the kernel implementation): #define SECTIONS_SHIFT (MAX_PHYSMEM_BITS - SECTION_SIZE_BITS) Now, regressions have been reported in user-space utilities like 'makedumpfile' and 'crash' on arm64, with the recently added kernel support for 52-bit physical address space, as there is no clear method of determining this value in user-space (other than reading kernel CONFIG flags). As per suggestion from makedumpfile maintainer (Kazu), it makes more sense to append 'MAX_PHYSMEM_BITS' to vmcoreinfo in the core code itself rather than in arch-specific code, so that the user-space code for other archs can also benefit from this addition to the vmcoreinfo and use it as a standard way of determining 'SECTIONS_SHIFT' value in user-land. A reference 'makedumpfile' implementation which reads the 'MAX_PHYSMEM_BITS' value from vmcoreinfo in a arch-independent fashion is available here: [0]. https://github.com/bhupesh-sharma/makedumpfile/blob/remove-max-phys-me= m-bit-v1/arch/ppc64.c#L471 Cc: Boris Petkov Cc: Ingo Molnar Cc: Thomas Gleixner Cc: James Morse Cc: Mark Rutland Cc: Will Deacon Cc: Steve Capper Cc: Catalin Marinas Cc: Ard Biesheuvel Cc: Michael Ellerman Cc: Paul Mackerras Cc: Benjamin Herrenschmidt Cc: Dave Anderson Cc: Kazuhito Hagio Cc: x86@kernel.org Cc: linuxppc-dev@lists.ozlabs.org Cc: linux-arm-kernel@lists.infradead.org Cc: linux-kernel@vger.kernel.org Cc: kexec@lists.infradead.org Signed-off-by: Bhupesh Sharma --- kernel/crash_core.c | 1 + 1 file changed, 1 insertion(+) diff --git a/kernel/crash_core.c b/kernel/crash_core.c index 9f1557b98468..18175687133a 100644 --- a/kernel/crash_core.c +++ b/kernel/crash_core.c @@ -413,6 +413,7 @@ static int __init crash_save_vmcoreinfo_init(void) =09VMCOREINFO_LENGTH(mem_section, NR_SECTION_ROOTS); =09VMCOREINFO_STRUCT_SIZE(mem_section); =09VMCOREINFO_OFFSET(mem_section, section_mem_map); +=09VMCOREINFO_NUMBER(MAX_PHYSMEM_BITS); #endif =09VMCOREINFO_STRUCT_SIZE(page); =09VMCOREINFO_STRUCT_SIZE(pglist_data); --=20 2.7.4 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=-14.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable 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 CAEB2C432C0 for ; Fri, 29 Nov 2019 20:05:14 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (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 6FAFF21721 for ; 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Fri, 29 Nov 2019 11:59:35 -0800 (PST) Received: from localhost ([122.177.85.74]) by smtp.gmail.com with ESMTPSA id r28sm23294033pgk.75.2019.11.29.11.59.33 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 29 Nov 2019 11:59:34 -0800 (PST) From: Bhupesh Sharma To: linux-kernel@vger.kernel.org Subject: [RESEND PATCH v5 1/5] crash_core, vmcoreinfo: Append 'MAX_PHYSMEM_BITS' to vmcoreinfo Date: Sat, 30 Nov 2019 01:29:15 +0530 Message-Id: <1575057559-25496-2-git-send-email-bhsharma@redhat.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1575057559-25496-1-git-send-email-bhsharma@redhat.com> References: <1575057559-25496-1-git-send-email-bhsharma@redhat.com> X-MC-Unique: nE0_eEn2Ox-JFPOu8HTqmw-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , Ard Biesheuvel , linux-doc@vger.kernel.org, Will Deacon , bhsharma@redhat.com, x86@kernel.org, kexec@lists.infradead.org, Dave Anderson , Paul Mackerras , Kazuhito Hagio , Boris Petkov , Catalin Marinas , James Morse , Thomas Gleixner , bhupesh.linux@gmail.com, linuxppc-dev@lists.ozlabs.org, Ingo Molnar , linux-arm-kernel@lists.infradead.org, Steve Capper Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Right now user-space tools like 'makedumpfile' and 'crash' need to rely on a best-guess method of determining value of 'MAX_PHYSMEM_BITS' supported by underlying kernel. This value is used in user-space code to calculate the bit-space required to store a section for SPARESMEM (similar to the existing calculation method used in the kernel implementation): #define SECTIONS_SHIFT (MAX_PHYSMEM_BITS - SECTION_SIZE_BITS) Now, regressions have been reported in user-space utilities like 'makedumpfile' and 'crash' on arm64, with the recently added kernel support for 52-bit physical address space, as there is no clear method of determining this value in user-space (other than reading kernel CONFIG flags). As per suggestion from makedumpfile maintainer (Kazu), it makes more sense to append 'MAX_PHYSMEM_BITS' to vmcoreinfo in the core code itself rather than in arch-specific code, so that the user-space code for other archs can also benefit from this addition to the vmcoreinfo and use it as a standard way of determining 'SECTIONS_SHIFT' value in user-land. A reference 'makedumpfile' implementation which reads the 'MAX_PHYSMEM_BITS' value from vmcoreinfo in a arch-independent fashion is available here: [0]. https://github.com/bhupesh-sharma/makedumpfile/blob/remove-max-phys-me= m-bit-v1/arch/ppc64.c#L471 Cc: Boris Petkov Cc: Ingo Molnar Cc: Thomas Gleixner Cc: James Morse Cc: Mark Rutland Cc: Will Deacon Cc: Steve Capper Cc: Catalin Marinas Cc: Ard Biesheuvel Cc: Michael Ellerman Cc: Paul Mackerras Cc: Benjamin Herrenschmidt Cc: Dave Anderson Cc: Kazuhito Hagio Cc: x86@kernel.org Cc: linuxppc-dev@lists.ozlabs.org Cc: linux-arm-kernel@lists.infradead.org Cc: linux-kernel@vger.kernel.org Cc: kexec@lists.infradead.org Signed-off-by: Bhupesh Sharma --- kernel/crash_core.c | 1 + 1 file changed, 1 insertion(+) diff --git a/kernel/crash_core.c b/kernel/crash_core.c index 9f1557b98468..18175687133a 100644 --- a/kernel/crash_core.c +++ b/kernel/crash_core.c @@ -413,6 +413,7 @@ static int __init crash_save_vmcoreinfo_init(void) =09VMCOREINFO_LENGTH(mem_section, NR_SECTION_ROOTS); =09VMCOREINFO_STRUCT_SIZE(mem_section); =09VMCOREINFO_OFFSET(mem_section, section_mem_map); +=09VMCOREINFO_NUMBER(MAX_PHYSMEM_BITS); #endif =09VMCOREINFO_STRUCT_SIZE(page); =09VMCOREINFO_STRUCT_SIZE(pglist_data); --=20 2.7.4 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=-14.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable 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 4FB74C432C0 for ; Fri, 29 Nov 2019 20:00:18 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 1A2FC2158A for ; 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Fri, 29 Nov 2019 11:59:35 -0800 (PST) X-Google-Smtp-Source: APXvYqxxfC5l5m0YoqdbJOwab9vDMWknIRaUJM6sjnSau+oJsA046vHWiBYg3wYv5hDxMjiI/P8T+w== X-Received: by 2002:a63:6f4c:: with SMTP id k73mr15574178pgc.374.1575057575265; Fri, 29 Nov 2019 11:59:35 -0800 (PST) Received: from localhost ([122.177.85.74]) by smtp.gmail.com with ESMTPSA id r28sm23294033pgk.75.2019.11.29.11.59.33 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 29 Nov 2019 11:59:34 -0800 (PST) From: Bhupesh Sharma To: linux-kernel@vger.kernel.org Subject: [RESEND PATCH v5 1/5] crash_core, vmcoreinfo: Append 'MAX_PHYSMEM_BITS' to vmcoreinfo Date: Sat, 30 Nov 2019 01:29:15 +0530 Message-Id: <1575057559-25496-2-git-send-email-bhsharma@redhat.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1575057559-25496-1-git-send-email-bhsharma@redhat.com> References: <1575057559-25496-1-git-send-email-bhsharma@redhat.com> X-MC-Unique: j6cAnfqxN-i9sl7R1MkLrg-1 X-Mimecast-Spam-Score: 0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20191129_115943_334686_90164072 X-CRM114-Status: GOOD ( 17.10 ) 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 , Ard Biesheuvel , Benjamin Herrenschmidt , linux-doc@vger.kernel.org, Will Deacon , bhsharma@redhat.com, x86@kernel.org, kexec@lists.infradead.org, Dave Anderson , Paul Mackerras , Kazuhito Hagio , Boris Petkov , Michael Ellerman , Catalin Marinas , James Morse , Thomas Gleixner , bhupesh.linux@gmail.com, linuxppc-dev@lists.ozlabs.org, Ingo Molnar , linux-arm-kernel@lists.infradead.org, Steve Capper MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org Right now user-space tools like 'makedumpfile' and 'crash' need to rely on a best-guess method of determining value of 'MAX_PHYSMEM_BITS' supported by underlying kernel. This value is used in user-space code to calculate the bit-space required to store a section for SPARESMEM (similar to the existing calculation method used in the kernel implementation): #define SECTIONS_SHIFT (MAX_PHYSMEM_BITS - SECTION_SIZE_BITS) Now, regressions have been reported in user-space utilities like 'makedumpfile' and 'crash' on arm64, with the recently added kernel support for 52-bit physical address space, as there is no clear method of determining this value in user-space (other than reading kernel CONFIG flags). As per suggestion from makedumpfile maintainer (Kazu), it makes more sense to append 'MAX_PHYSMEM_BITS' to vmcoreinfo in the core code itself rather than in arch-specific code, so that the user-space code for other archs can also benefit from this addition to the vmcoreinfo and use it as a standard way of determining 'SECTIONS_SHIFT' value in user-land. A reference 'makedumpfile' implementation which reads the 'MAX_PHYSMEM_BITS' value from vmcoreinfo in a arch-independent fashion is available here: [0]. https://github.com/bhupesh-sharma/makedumpfile/blob/remove-max-phys-mem-bit-v1/arch/ppc64.c#L471 Cc: Boris Petkov Cc: Ingo Molnar Cc: Thomas Gleixner Cc: James Morse Cc: Mark Rutland Cc: Will Deacon Cc: Steve Capper Cc: Catalin Marinas Cc: Ard Biesheuvel Cc: Michael Ellerman Cc: Paul Mackerras Cc: Benjamin Herrenschmidt Cc: Dave Anderson Cc: Kazuhito Hagio Cc: x86@kernel.org Cc: linuxppc-dev@lists.ozlabs.org Cc: linux-arm-kernel@lists.infradead.org Cc: linux-kernel@vger.kernel.org Cc: kexec@lists.infradead.org Signed-off-by: Bhupesh Sharma --- kernel/crash_core.c | 1 + 1 file changed, 1 insertion(+) diff --git a/kernel/crash_core.c b/kernel/crash_core.c index 9f1557b98468..18175687133a 100644 --- a/kernel/crash_core.c +++ b/kernel/crash_core.c @@ -413,6 +413,7 @@ static int __init crash_save_vmcoreinfo_init(void) VMCOREINFO_LENGTH(mem_section, NR_SECTION_ROOTS); VMCOREINFO_STRUCT_SIZE(mem_section); VMCOREINFO_OFFSET(mem_section, section_mem_map); + VMCOREINFO_NUMBER(MAX_PHYSMEM_BITS); #endif VMCOREINFO_STRUCT_SIZE(page); VMCOREINFO_STRUCT_SIZE(pglist_data); -- 2.7.4 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120] helo=us-smtp-1.mimecast.com) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1iamQW-00074G-88 for kexec@lists.infradead.org; Fri, 29 Nov 2019 19:59:42 +0000 Received: by mail-pf1-f198.google.com with SMTP id o71so7300966pfg.22 for ; Fri, 29 Nov 2019 11:59:36 -0800 (PST) From: Bhupesh Sharma Subject: [RESEND PATCH v5 1/5] crash_core, vmcoreinfo: Append 'MAX_PHYSMEM_BITS' to vmcoreinfo Date: Sat, 30 Nov 2019 01:29:15 +0530 Message-Id: <1575057559-25496-2-git-send-email-bhsharma@redhat.com> In-Reply-To: <1575057559-25496-1-git-send-email-bhsharma@redhat.com> References: <1575057559-25496-1-git-send-email-bhsharma@redhat.com> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "kexec" Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: linux-kernel@vger.kernel.org Cc: Mark Rutland , Ard Biesheuvel , Benjamin Herrenschmidt , linux-doc@vger.kernel.org, Will Deacon , bhsharma@redhat.com, x86@kernel.org, kexec@lists.infradead.org, Dave Anderson , Paul Mackerras , Kazuhito Hagio , Boris Petkov , Michael Ellerman , Catalin Marinas , James Morse , Thomas Gleixner , bhupesh.linux@gmail.com, linuxppc-dev@lists.ozlabs.org, Ingo Molnar , linux-arm-kernel@lists.infradead.org, Steve Capper Right now user-space tools like 'makedumpfile' and 'crash' need to rely on a best-guess method of determining value of 'MAX_PHYSMEM_BITS' supported by underlying kernel. This value is used in user-space code to calculate the bit-space required to store a section for SPARESMEM (similar to the existing calculation method used in the kernel implementation): #define SECTIONS_SHIFT (MAX_PHYSMEM_BITS - SECTION_SIZE_BITS) Now, regressions have been reported in user-space utilities like 'makedumpfile' and 'crash' on arm64, with the recently added kernel support for 52-bit physical address space, as there is no clear method of determining this value in user-space (other than reading kernel CONFIG flags). As per suggestion from makedumpfile maintainer (Kazu), it makes more sense to append 'MAX_PHYSMEM_BITS' to vmcoreinfo in the core code itself rather than in arch-specific code, so that the user-space code for other archs can also benefit from this addition to the vmcoreinfo and use it as a standard way of determining 'SECTIONS_SHIFT' value in user-land. A reference 'makedumpfile' implementation which reads the 'MAX_PHYSMEM_BITS' value from vmcoreinfo in a arch-independent fashion is available here: [0]. https://github.com/bhupesh-sharma/makedumpfile/blob/remove-max-phys-mem-bit-v1/arch/ppc64.c#L471 Cc: Boris Petkov Cc: Ingo Molnar Cc: Thomas Gleixner Cc: James Morse Cc: Mark Rutland Cc: Will Deacon Cc: Steve Capper Cc: Catalin Marinas Cc: Ard Biesheuvel Cc: Michael Ellerman Cc: Paul Mackerras Cc: Benjamin Herrenschmidt Cc: Dave Anderson Cc: Kazuhito Hagio Cc: x86@kernel.org Cc: linuxppc-dev@lists.ozlabs.org Cc: linux-arm-kernel@lists.infradead.org Cc: linux-kernel@vger.kernel.org Cc: kexec@lists.infradead.org Signed-off-by: Bhupesh Sharma --- kernel/crash_core.c | 1 + 1 file changed, 1 insertion(+) diff --git a/kernel/crash_core.c b/kernel/crash_core.c index 9f1557b98468..18175687133a 100644 --- a/kernel/crash_core.c +++ b/kernel/crash_core.c @@ -413,6 +413,7 @@ static int __init crash_save_vmcoreinfo_init(void) VMCOREINFO_LENGTH(mem_section, NR_SECTION_ROOTS); VMCOREINFO_STRUCT_SIZE(mem_section); VMCOREINFO_OFFSET(mem_section, section_mem_map); + VMCOREINFO_NUMBER(MAX_PHYSMEM_BITS); #endif VMCOREINFO_STRUCT_SIZE(page); VMCOREINFO_STRUCT_SIZE(pglist_data); -- 2.7.4 _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec