Message-ID: <CACi5LpNYtAFq6PYjsYArViz+gzuh5-_CKZLBqo826oWhERrx8A@mail.gmail.com>
Date:   Tue, 16 Jun 2020 00:41:37 +0530
From:   Bhupesh Sharma <bhsharma@...hat.com>
To:     linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        x86@...nel.org, Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>
Cc:     Bhupesh SHARMA <bhupesh.linux@...il.com>,
        Boris Petkov <bp@...en8.de>, Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jonathan Corbet <corbet@....net>,
        James Morse <james.morse@....com>,
        Mark Rutland <mark.rutland@....com>,
        Steve Capper <steve.capper@....com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Paul Mackerras <paulus@...ba.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Dave Anderson <anderson@...hat.com>,
        Kazuhito Hagio <k-hagio@...jp.nec.com>,
        John Donnelly <john.p.donnelly@...cle.com>,
        Scott Branden <scott.branden@...adcom.com>,
        Amit Kachhap <amit.kachhap@....com>,
        linuxppc-dev@...ts.ozlabs.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Doc Mailing List <linux-doc@...r.kernel.org>,
        kexec mailing list <kexec@...ts.infradead.org>
Subject: Re: [PATCH v6 0/2] Append new variables to vmcoreinfo (TCR_EL1.T1SZ
 for arm64 and MAX_PHYSMEM_BITS for all archs)

Hello Catalin, Will,

On Tue, Jun 2, 2020 at 10:54 AM Bhupesh Sharma <bhsharma@...hat.com> wrote:
>
> Hello,
>
> On Thu, May 14, 2020 at 12:22 AM Bhupesh Sharma <bhsharma@...hat.com> wrote:
> >
> > Apologies for the delayed update. Its been quite some time since I
> > posted the last version (v5), but I have been really caught up in some
> > other critical issues.
> >
> > Changes since v5:
> > ----------------
> > - v5 can be viewed here:
> >   http://lists.infradead.org/pipermail/kexec/2019-November/024055.html
> > - Addressed review comments from James Morse and Boris.
> > - Added Tested-by received from John on v5 patchset.
> > - Rebased against arm64 (for-next/ptr-auth) branch which has Amit's
> >   patchset for ARMv8.3-A Pointer Authentication feature vmcoreinfo
> >   applied.
> >
> > 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@...en8.de>
> > Cc: Ingo Molnar <mingo@...nel.org>
> > Cc: Thomas Gleixner <tglx@...utronix.de>
> > Cc: Jonathan Corbet <corbet@....net>
> > Cc: James Morse <james.morse@....com>
> > Cc: Mark Rutland <mark.rutland@....com>
> > Cc: Will Deacon <will@...nel.org>
> > Cc: Steve Capper <steve.capper@....com>
> > Cc: Catalin Marinas <catalin.marinas@....com>
> > Cc: Ard Biesheuvel <ard.biesheuvel@...aro.org>
> > Cc: Michael Ellerman <mpe@...erman.id.au>
> > Cc: Paul Mackerras <paulus@...ba.org>
> > Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
> > Cc: Dave Anderson <anderson@...hat.com>
> > Cc: Kazuhito Hagio <k-hagio@...jp.nec.com>
> > Cc: John Donnelly <john.p.donnelly@...cle.com>
> > Cc: scott.branden@...adcom.com
> > Cc: Amit Kachhap <amit.kachhap@....com>
> > Cc: x86@...nel.org
> > Cc: linuxppc-dev@...ts.ozlabs.org
> > Cc: linux-arm-kernel@...ts.infradead.org
> > Cc: linux-kernel@...r.kernel.org
> > Cc: linux-doc@...r.kernel.org
> > Cc: kexec@...ts.infradead.org
> >
> > Bhupesh Sharma (2):
> >   crash_core, vmcoreinfo: Append 'MAX_PHYSMEM_BITS' to vmcoreinfo
> >   arm64/crash_core: Export TCR_EL1.T1SZ in vmcoreinfo
> >
> >  Documentation/admin-guide/kdump/vmcoreinfo.rst | 16 ++++++++++++++++
> >  arch/arm64/include/asm/pgtable-hwdef.h         |  1 +
> >  arch/arm64/kernel/crash_core.c                 | 10 ++++++++++
> >  kernel/crash_core.c                            |  1 +
> >  4 files changed, 28 insertions(+)
>
> Ping. @James Morse , Others
>
> Please share if you have some comments regarding this patchset.

Ping. I think we have two Tested-by available from Oracle and Marvell
folks on this patchset and no further review-comments.
Can you please help review/pick this patchset via the arm64 tree?

User-space utilities like makedumpfile and crash have been broken
since 52-bit VA addressing was enabled on arm64 kernel, so distros are
obliged to carry downstream-only fixes for these user-space utilities
to make them work with the kernel which support 52-bit VA addressing
on arm64.

Thanks,
Bhupesh

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