Re: [PATCH v4 0/3] Append new variables to vmcoreinfo (TCR_EL1.T1SZ for arm64 and MAX_PHYSMEM_BITS for all archs)

[Bhupesh Sharma]

Hi Akashi,

On Wed, Nov 13, 2019 at 12:11 PM AKASHI Takahiro
<takahiro.akashi@xxxxxxxxxx> wrote:
>
> Hi Bhupesh,
>
> Do you have a corresponding patch for userspace tools,
> including crash util and/or makedumpfile?
> Otherwise, we can't verify that a generated core file is
> correctly handled.

Sure. I am still working on the crash-utility related changes, but you
can find the makedumpfile changes I posted a couple of days ago here
(see [0]) and the github link for the makedumpfile changes can be seen
via [1].

I will post the crash-util changes shortly as well.
Thanks for having a look at the same.

[0]. http://lists.infradead.org/pipermail/kexec/2019-November/023963.html
[1]. https://github.com/bhupesh-sharma/makedumpfile/tree/52-bit-va-support-via-vmcore-upstream-v4

Regards,
Bhupesh

>
> Thanks,
> -Takahiro Akashi
>
> On Mon, Nov 11, 2019 at 01:31:19PM +0530, Bhupesh Sharma wrote:
> > 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@xxxxxxxxx>
> > Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> > Cc: Jonathan Corbet <corbet@xxxxxxx>
> > Cc: James Morse <james.morse@xxxxxxx>
> > Cc: Mark Rutland <mark.rutland@xxxxxxx>
> > Cc: Will Deacon <will@xxxxxxxxxx>
> > Cc: Steve Capper <steve.capper@xxxxxxx>
> > Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
> > Cc: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
> > Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
> > Cc: Paul Mackerras <paulus@xxxxxxxxx>
> > Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
> > Cc: Dave Anderson <anderson@xxxxxxxxxx>
> > Cc: Kazuhito Hagio <k-hagio@xxxxxxxxxxxxx>
> > Cc: x86@xxxxxxxxxx
> > Cc: linuxppc-dev@xxxxxxxxxxxxxxxx
> > Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
> > Cc: linux-kernel@xxxxxxxxxxxxxxx
> > Cc: linux-doc@xxxxxxxxxxxxxxx
> > Cc: kexec@xxxxxxxxxxxxxxxxxxx
> >
> > Bhupesh Sharma (3):
> >   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/arm64/memory.rst         | 2 +-
> >  arch/arm64/include/asm/pgtable-hwdef.h | 1 +
> >  arch/arm64/kernel/crash_core.c         | 9 +++++++++
> >  kernel/crash_core.c                    | 1 +
> >  4 files changed, 12 insertions(+), 1 deletion(-)
> >
> > --
> > 2.7.4
> >
>