From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120] helo=us-smtp-1.mimecast.com) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1jYwUs-0003Ie-DW for kexec@lists.infradead.org; Wed, 13 May 2020 18:52:52 +0000 Received: by mail-pf1-f197.google.com with SMTP id 126so488460pfd.10 for ; Wed, 13 May 2020 11:52:47 -0700 (PDT) From: Bhupesh Sharma Subject: [PATCH v6 1/2] crash_core, vmcoreinfo: Append 'MAX_PHYSMEM_BITS' to vmcoreinfo Date: Thu, 14 May 2020 00:22:36 +0530 Message-Id: <1589395957-24628-2-git-send-email-bhsharma@redhat.com> In-Reply-To: <1589395957-24628-1-git-send-email-bhsharma@redhat.com> References: <1589395957-24628-1-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-arm-kernel@lists.infradead.org, x86@kernel.org Cc: Mark Rutland , Kazuhito Hagio , Michael Ellerman , bhsharma@redhat.com, kexec@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, James Morse , Benjamin Herrenschmidt , Boris Petkov , Thomas Gleixner , bhupesh.linux@gmail.com, Will Deacon , Ingo Molnar , Paul Mackerras , Dave Anderson 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: While at it also update vmcoreinfo documentation for 'MAX_PHYSMEM_BITS' variable being added to vmcoreinfo. 'MAX_PHYSMEM_BITS' defines the maximum supported physical address space memory. Cc: Boris Petkov Cc: Ingo Molnar Cc: Thomas Gleixner Cc: James Morse Cc: Mark Rutland Cc: Will Deacon 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 Tested-by: John Donnelly Signed-off-by: Bhupesh Sharma --- Documentation/admin-guide/kdump/vmcoreinfo.rst | 5 +++++ kernel/crash_core.c | 1 + 2 files changed, 6 insertions(+) diff --git a/Documentation/admin-guide/kdump/vmcoreinfo.rst b/Documentation/admin-guide/kdump/vmcoreinfo.rst index e4ee8b2db604..2a632020f809 100644 --- a/Documentation/admin-guide/kdump/vmcoreinfo.rst +++ b/Documentation/admin-guide/kdump/vmcoreinfo.rst @@ -93,6 +93,11 @@ It exists in the sparse memory mapping model, and it is also somewhat similar to the mem_map variable, both of them are used to translate an address. +MAX_PHYSMEM_BITS +---------------- + +Defines the maximum supported physical address space memory. + page ---- 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