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Fri, 29 Nov 2019 11:29:14 -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 00:58:42 +0530 Message-Id: <1575055726-23464-2-git-send-email-bhsharma@redhat.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1575055726-23464-1-git-send-email-bhsharma@redhat.com> References: <1575055726-23464-1-git-send-email-bhsharma@redhat.com> X-MC-Unique: 5j9csuYxOMqKucOXH9UOTw-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