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Tue, 8 Jun 2021 14:24:35 +0000 (UTC) Date: Tue, 8 Jun 2021 22:24:32 +0800 From: Baoquan He To: Pingfan Liu Subject: Re: [PATCH] crash_core, vmcoreinfo: Append 'SECTION_SIZE_BITS' to vmcoreinfo Message-ID: <20210608142432.GA587883@MiWiFi-R3L-srv> References: <20210608103359.84907-1-kernelfans@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210608103359.84907-1-kernelfans@gmail.com> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 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 , x86@kernel.org, Kazuhito Hagio , Thomas Gleixner , Bhupesh Sharma , linux-arm-kernel@lists.infradead.org, Will Deacon , linuxppc-dev@lists.ozlabs.org, kexec@lists.infradead.org, Dave Anderson , linux-kernel@vger.kernel.org, Boris Petkov , Catalin Marinas , James Morse , akpm@linux-foundation.org, Dave Young , Ingo Molnar , Paul Mackerras Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 06/08/21 at 06:33am, Pingfan Liu wrote: > As mentioned in kernel commit 1d50e5d0c505 ("crash_core, vmcoreinfo: > Append 'MAX_PHYSMEM_BITS' to vmcoreinfo"), SECTION_SIZE_BITS in the > formula: > #define SECTIONS_SHIFT (MAX_PHYSMEM_BITS - SECTION_SIZE_BITS) > > Besides SECTIONS_SHIFT, SECTION_SIZE_BITS is also used to calculate > PAGES_PER_SECTION in makedumpfile just like kernel. > > Unfortunately, this arch-dependent macro SECTION_SIZE_BITS changes, e.g. > recently in kernel commit f0b13ee23241 ("arm64/sparsemem: reduce > SECTION_SIZE_BITS"). But user space wants a stable interface to get this > info. Such info is impossible to be deduced from a crashdump vmcore. > Hence append SECTION_SIZE_BITS to vmcoreinfo. > > Signed-off-by: Pingfan Liu > Cc: Bhupesh Sharma > Cc: Kazuhito Hagio > Cc: Dave Young > Cc: Baoquan He > Cc: Boris Petkov > Cc: Ingo Molnar > Cc: Thomas Gleixner > Cc: James Morse > Cc: Mark Rutland > Cc: Will Deacon > Cc: Catalin Marinas > Cc: Michael Ellerman > Cc: Paul Mackerras > Cc: Benjamin Herrenschmidt > Cc: Dave Anderson > Cc: linuxppc-dev@lists.ozlabs.org > Cc: linux-kernel@vger.kernel.org > Cc: kexec@lists.infradead.org > Cc: x86@kernel.org > Cc: linux-arm-kernel@lists.infradead.org Add the discussion of the original thread in kexec ML for reference: http://lists.infradead.org/pipermail/kexec/2021-June/022676.html This looks good to me. Acked-by: Baoquan He > --- > kernel/crash_core.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/kernel/crash_core.c b/kernel/crash_core.c > index 825284baaf46..684a6061a13a 100644 > --- a/kernel/crash_core.c > +++ b/kernel/crash_core.c > @@ -464,6 +464,7 @@ 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(SECTION_SIZE_BITS); > VMCOREINFO_NUMBER(MAX_PHYSMEM_BITS); > #endif > VMCOREINFO_STRUCT_SIZE(page); > -- > 2.29.2 >