Re: [PATCH] crash_core, vmcoreinfo: Append 'SECTION_SIZE_BITS' to vmcoreinfo
From: Baoquan He <hidden>
Date: 2021-06-08 14:24:57
Also in:
kexec, linux-arm-kernel, lkml
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 <redacted> Cc: Bhupesh Sharma <redacted> Cc: Kazuhito Hagio <redacted> Cc: Dave Young <redacted> Cc: Baoquan He <redacted> Cc: Boris Petkov <bp@alien8.de> Cc: Ingo Molnar <mingo@kernel.org> Cc: Thomas Gleixner <redacted> Cc: James Morse <james.morse@arm.com> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Will Deacon <will@kernel.org> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Paul Mackerras <redacted> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Dave Anderson <redacted> 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 <redacted>
quoted hunk ↗ jump to hunk
--- 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