[PATCH v5 0/3] makedumpfile/arm64: Add support for ARMv8.2 extensions

[HAGIO KAZUHITO(萩尾 一仁)]

Hi Bhupesh,

-----Original Message-----
> Hi Bhupesh,
> 
> sorry for my scattered comments.
> 
> As for 1/3 and 2/3, I think we can merge them separately with 3/3, right?
> so if you can ack the updated 1/3 I sent, I will merge them first.
> Could you check it?

Hopefully I'd like to release the next version of makedumpfile next week.

So I'm going to merge the modified 1/3 patch and your 2/3 patch separately
from 3/3, I think it can use "MAX_PHYSMEM_BITS" and reduce distribution-specific
patches.  If you have any concerns about it, please let me know.

Thanks,
Kazu

> 
> As for 3/3, you introduced a couple of new ways, so I'd like to discuss
> whether there is no better way a little more.
> 
> Thanks,
> Kazu
> 
> -----Original Message-----
> > Changes since v4:
> > ----------------
> > - v4 can be seen here:
> >   https://www.spinics.net/lists/kexec/msg23850.html
> > - Removed the patch (via [PATCH 4/4] in v3) which marked '--mem-usage'
> >   option as unsupported for arm64 architecture, as we now have a mechanism
> >   to read the 'vabits_actual' value from 'id_aa64mmfr2_el1' arm64 system
> >   architecture register. As per discussions with arm64 and gcc/binutils
> >   maintainers it turns out there is no standard ABI available between
> >   the kernel and user-space to export this value early enough to be used
> >   for page_offset calculation in the --mem-usage case. So, the next best
> >   option is to have the user-space read the system register to determine
> >   underlying hardware support for larger (52-bit) addressing support.
> >
> >   This allows us to keep supporting '--mem-usage' option on arm64 even
> >   on newer kernels (with flipped VA space).
> >
> > Changes since v3:
> > ----------------
> > - v3 can be seen here:
> >   http://lists.infradead.org/pipermail/kexec/2019-March/022534.html
> > - Added a new patch (via [PATCH 4/4]) which marks '--mem-usage' option as
> >   unsupported for arm64 architecture. With the newer arm64 kernels
> >   supporting 48-bit/52-bit VA address spaces and keeping a single
> >   binary for supporting the same, the address of
> >   kernel symbols like _stext, which could be earlier used to determine
> >   VA_BITS value, can no longer to determine whether VA_BITS is set to 48
> >   or 52 in the kernel space. Hence for now, it makes sense to mark
> >   '--mem-usage' option as unsupported for arm64 architecture until
> >   we have more clarity from arm64 kernel maintainers on how to manage
> >   the same in future kernel/makedumpfile versions.
> >
> > Changes since v2:
> > ----------------
> > - v2 can be seen here:
> >   http://lists.infradead.org/pipermail/kexec/2019-February/022456.html
> > - I missed some comments from Kazu sent on the LVA v1 patch when I sent
> >   out the v2. So, addressing them now in v3.
> > - Also added a patch that adds a tree-wide feature to read
> >   'MAX_PHYSMEM_BITS' from vmcoreinfo (if available).
> >
> > Changes since v1:
> > ----------------
> > - v1 was sent as two separate patches:
> >   http://lists.infradead.org/pipermail/kexec/2019-February/022424.html
> >   (ARMv8.2-LPA)
> >   http://lists.infradead.org/pipermail/kexec/2019-February/022425.html
> >   (ARMv8.2-LVA)
> > - v2 combined the two in a single patchset and also addresses Kazu's
> >   review comments.
> >
> > This patchset adds support for ARMv8.2 extensions in makedumpfile code.
> > I cover the following cases with this patchset:
> > - Both old (<5.4) and new kernels (>= 5.4) work well.
> > - All VA and PA bit combinations currently supported via the kernel
> >   CONFIG options work well, including:
> >  - 48-bit kernel VA + 52-bit PA (LPA)
> >  - 52-bit kernel VA (LVA) + 52-bit PA (LPA)
> >
> > This has been tested for the following user-cases:
> > 1. Analysing page information via '--mem-usage' option.
> > 2. Creating a dumpfile using /proc/vmcore,
> > 3. Creating a dumpfile using /proc/kcore, and
> > 4. Post-processing a vmcore.
> >
> > I have tested this patchset on the following platforms, with kernels
> > which support/do-not-support ARMv8.2 features:
> > 1. CPUs which don't support ARMv8.2 features, e.g. qualcomm-amberwing,
> >    ampere-osprey.
> > 2. Prototype models which support ARMv8.2 extensions (e.g. ARMv8 FVP
> >    simulation model).
> >
> > Also a preparation patch has been added in this patchset which adds a
> > common feature for archs (except arm64, for which similar support is
> > added via subsequent patch) to retrieve 'MAX_PHYSMEM_BITS' from
> > vmcoreinfo (if available).
> >
> > This patchset ensures backward compatibility for kernel versions in
> > which 'TCR_EL1.T1SZ' and 'MAX_PHYSMEM_BITS' are not available in
> > vmcoreinfo.
> >
> > In the newer kernels (>= 5.4.0) the following patches export these
> > variables in the vmcoreinfo:
> >  - 1d50e5d0c505 ("crash_core, vmcoreinfo: Append 'MAX_PHYSMEM_BITS' to vmcoreinfo")
> >  - bbdbc11804ff ("arm64/crash_core: Export TCR_EL1.T1SZ in vmcoreinfo")
> >
> > Cc: John Donnelly <john.p.donnelly at oracle.com>
> > Cc: Kazuhito Hagio <k-hagio at ab.jp.nec.com>
> > Cc: kexec at lists.infradead.org
> >
> > Bhupesh Sharma (3):
> >   tree-wide: Retrieve 'MAX_PHYSMEM_BITS' from vmcoreinfo (if available)
> >   makedumpfile/arm64: Add support for ARMv8.2-LPA (52-bit PA support)
> >   makedumpfile/arm64: Add support for ARMv8.2-LVA (52-bit kernel VA
> >     support)
> >
> >  arch/arm.c     |   8 +-
> >  arch/arm64.c   | 520 ++++++++++++++++++++++++++++++++++++++-----------
> >  arch/ia64.c    |   7 +-
> >  arch/ppc.c     |   8 +-
> >  arch/ppc64.c   |  49 +++--
> >  arch/s390x.c   |  29 +--
> >  arch/sparc64.c |   9 +-
> >  arch/x86.c     |  34 ++--
> >  arch/x86_64.c  |  27 +--
> >  common.h       |  10 +
> >  makedumpfile.c |   4 +-
> >  makedumpfile.h |   6 +-
> >  12 files changed, 529 insertions(+), 182 deletions(-)
> >
> > --
> > 2.26.2
> 
> 
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