[PATCH v5 0/5] Append new variables to vmcoreinfo (TCR_EL1.T1SZ for arm64 and MAX_PHYSMEM_BITS for all archs)

Bhupesh Sharma
2019-11-28T20:24:09Z

Changes since v4:
----------------
- v4 can be seen here:
http://lists.infradead.org/pipermail/kexec/2019-November/023961.html
- Addressed comments from Dave and added patches for documenting
new variables appended to vmcoreinfo documentation.
- Added testing report shared by Akashi for PATCH 2/5.

Changes since v3:
----------------
- v3 can be seen here:
http://lists.infradead.org/pipermail/kexec/2019-March/022590.html
- Addressed comments from James and exported TCR_EL1.T1SZ in vmcoreinfo
instead of PTRS_PER_PGD.
- Added a new patch (via [PATCH 3/3]), which fixes a simple typo in
'Documentation/arm64/memory.rst'

Changes since v2:
----------------
- v2 can be seen here:
http://lists.infradead.org/pipermail/kexec/2019-March/022531.html
- Protected 'MAX_PHYSMEM_BITS' vmcoreinfo variable under CONFIG_SPARSEMEM
ifdef sections, as suggested by Kazu.
- Updated vmcoreinfo documentation to add description about
'MAX_PHYSMEM_BITS' variable (via [PATCH 3/3]).

Changes since v1:
----------------
- v1 was sent out as a single patch which can be seen here:
http://lists.infradead.org/pipermail/kexec/2019-February/022411.html

- v2 breaks the single patch into two independent patches:
[PATCH 1/2] appends 'PTRS_PER_PGD' to vmcoreinfo for arm64 arch, whereas
[PATCH 2/2] appends 'MAX_PHYSMEM_BITS' to vmcoreinfo in core kernel code (all archs)

This patchset primarily fixes the regression reported in user-space
utilities like 'makedumpfile' and 'crash-utility' on arm64 architecture
with the availability of 52-bit address space feature in underlying
kernel. These regressions have been reported both on CPUs which don't
support ARMv8.2 extensions (i.e. LVA, LPA) and are running newer kernels
and also on prototype platforms (like ARMv8 FVP simulator model) which
support ARMv8.2 extensions and are running newer kernels.

The reason for these regressions is that right now user-space tools
have no direct access to these values (since these are not exported
from the kernel) and hence need to rely on a best-guess method of
determining value of 'vabits_actual' and 'MAX_PHYSMEM_BITS' supported
by underlying kernel.

Exporting these values via vmcoreinfo will help user-land in such cases.
In addition, 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 arm64 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.

Cc: Boris Petkov <bp@alien8.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: James Morse <james.morse@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Steve Capper <steve.capper@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Dave Anderson <anderson@redhat.com>
Cc: Kazuhito Hagio <k-hagio@ab.jp.nec.com>
Cc: x86@kernel.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-doc@vger.kernel.org
Cc: kexec@lists.infradead.org

Bhupesh Sharma (5):
crash_core, vmcoreinfo: Append 'MAX_PHYSMEM_BITS' to vmcoreinfo
arm64/crash_core: Export TCR_EL1.T1SZ in vmcoreinfo
Documentation/arm64: Fix a simple typo in memory.rst
Documentation/vmcoreinfo: Add documentation for 'MAX_PHYSMEM_BITS'
Documentation/vmcoreinfo: Add documentation for 'TCR_EL1.T1SZ'

Documentation/admin-guide/kdump/vmcoreinfo.rst | 11 +++++++++++
Documentation/arm64/memory.rst | 2 +-
arch/arm64/include/asm/pgtable-hwdef.h | 1 +
arch/arm64/kernel/crash_core.c | 9 +++++++++
kernel/crash_core.c | 1 +
5 files changed, 23 insertions(+), 1 deletion(-)

--
2.7.4