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

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

[Bhupesh Sharma]

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

[PATCH v5 1/5] crash_core, vmcoreinfo: Append 'MAX_PHYSMEM_BITS' to vmcoreinfo

[Bhupesh Sharma]

Right now user-space tools like 'makedumpfile' and 'crash' need to rely
on a best-guess method of determining value of 'MAX_PHYSMEM_BITS'
supported by underlying kernel.

This value is used in user-space code to calculate the bit-space
required to store a section for SPARESMEM (similar to the existing
calculation method used in the kernel implementation):

  #define SECTIONS_SHIFT    (MAX_PHYSMEM_BITS - SECTION_SIZE_BITS)

Now, regressions have been reported in user-space utilities
like 'makedumpfile' and 'crash' on arm64, with the recently added
kernel support for 52-bit physical address space, as there is
no clear method of determining this value in user-space
(other than reading kernel CONFIG flags).

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 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.

A reference 'makedumpfile' implementation which reads the
'MAX_PHYSMEM_BITS' value from vmcoreinfo in a arch-independent fashion
is available here:

[0]. https://github.com/bhupesh-sharma/makedumpfile/blob/remove-max-phys-mem-bit-v1/arch/ppc64.c#L471

Cc: Boris Petkov <bp@alien8.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
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: kexec@lists.infradead.org
Signed-off-by: Bhupesh Sharma <bhsharma@redhat.com>
---
 kernel/crash_core.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/crash_core.c b/kernel/crash_core.c
index 9f1557b98468..18175687133a 100644
--- a/kernel/crash_core.c
+++ b/kernel/crash_core.c
@@ -413,6 +413,7 @@ 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(MAX_PHYSMEM_BITS);
 #endif
 	VMCOREINFO_STRUCT_SIZE(page);
 	VMCOREINFO_STRUCT_SIZE(pglist_data);
-- 
2.7.4

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

[Will Deacon]

On Fri, Nov 29, 2019 at 01:53:36AM +0530, Bhupesh Sharma wrote:
> 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.

Please can you fix your mail setup? The last two times you've sent this
series it seems to get split into two threads, which is really hard to
track in my inbox:

First thread:

https://lore.kernel.org/lkml/1574972621-25750-1-git-send-email-bhsharma@redhat.com/

Second thread:

https://lore.kernel.org/lkml/1574972716-25858-1-git-send-email-bhsharma@redhat.com/

Thanks,

Will

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

[Bhupesh Sharma]

Hi Will,

On Fri, Nov 29, 2019 at 3:54 PM Will Deacon <will@kernel.org> wrote:
>
> On Fri, Nov 29, 2019 at 01:53:36AM +0530, Bhupesh Sharma wrote:
> > 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.
>
> Please can you fix your mail setup? The last two times you've sent this
> series it seems to get split into two threads, which is really hard to
> track in my inbox:
>
> First thread:
>
> https://lore.kernel.org/lkml/1574972621-25750-1-git-send-email-bhsharma@redhat.com/
>
> Second thread:
>
> https://lore.kernel.org/lkml/1574972716-25858-1-git-send-email-bhsharma@redhat.com/

There seems to be some issue with my server's msmtp settings. I have
tried resending the v5 (see
<http://lists.infradead.org/pipermail/linux-arm-kernel/2019-November/696833.html>).

I hope the threading is ok this time.

Thanks for your patience.

Regards,
Bhupesh

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

[Will Deacon]

On Sat, Nov 30, 2019 at 01:35:36AM +0530, Bhupesh Sharma wrote:
> On Fri, Nov 29, 2019 at 3:54 PM Will Deacon <will@kernel.org> wrote:
> > On Fri, Nov 29, 2019 at 01:53:36AM +0530, Bhupesh Sharma wrote:
> > > 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.
> >
> > Please can you fix your mail setup? The last two times you've sent this
> > series it seems to get split into two threads, which is really hard to
> > track in my inbox:
> >
> > First thread:
> >
> > https://lore.kernel.org/lkml/1574972621-25750-1-git-send-email-bhsharma@redhat.com/
> >
> > Second thread:
> >
> > https://lore.kernel.org/lkml/1574972716-25858-1-git-send-email-bhsharma@redhat.com/
> 
> There seems to be some issue with my server's msmtp settings. I have
> tried resending the v5 (see
> <http://lists.infradead.org/pipermail/linux-arm-kernel/2019-November/696833.html>).
> 
> I hope the threading is ok this time.

Much better now, thanks for sorting it out.

Will

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

[Borislav Petkov]

On Fri, Nov 29, 2019 at 01:53:36AM +0530, Bhupesh Sharma wrote:
> 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'

why are those last two separate patches and not part of the patches
which export the respective variable/define?

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

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

[Bhupesh Sharma]

Hi Boris,

On Sat, Dec 14, 2019 at 5:57 PM Borislav Petkov <bp@alien8.de> wrote:
>
> On Fri, Nov 29, 2019 at 01:53:36AM +0530, Bhupesh Sharma wrote:
> > 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'
>
> why are those last two separate patches and not part of the patches
> which export the respective variable/define?

I remember there was a suggestion during the review of an earlier
version to keep them as a separate patch(es) so that the documentation
text is easier to review, but I have no strong preference towards the
same.

I can merge the documentation patches with the respective patches
(which export the variables/defines to vmcoreinfo) in v6, unless other
maintainers have an objections towards the same.

Thanks,
Bhupesh

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

[Borislav Petkov]

On Mon, Dec 16, 2019 at 12:16:12PM +0530, Bhupesh Sharma wrote:
> I remember there was a suggestion during the review of an earlier
> version to keep them as a separate patch(es) so that the documentation
> text is easier to review,

Documentation text is one sentence, respectively. Not really worth a
separate patch.

> I can merge the documentation patches with the respective patches
> (which export the variables/defines to vmcoreinfo) in v6,

Please do.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette