diff mbox series

[v6,1/2] crash_core, vmcoreinfo: Append 'MAX_PHYSMEM_BITS' to vmcoreinfo

Message ID 1589395957-24628-2-git-send-email-bhsharma@redhat.com (mailing list archive)
State Mainlined
Commit 1d50e5d0c5052446cb85a3bf11fe8ba4e8d770ca
Headers show
Series Append new variables to vmcoreinfo (TCR_EL1.T1SZ for arm64 and MAX_PHYSMEM_BITS for all archs) | expand

Commit Message

Bhupesh Sharma May 13, 2020, 6:52 p.m. UTC 
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:

While at it also update vmcoreinfo documentation for 'MAX_PHYSMEM_BITS'
variable being added to vmcoreinfo.

'MAX_PHYSMEM_BITS' defines the maximum supported physical address
space memory.

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: 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
Tested-by: John Donnelly <john.p.donnelly@oracle.com>
Signed-off-by: Bhupesh Sharma <bhsharma@redhat.com>
---
 Documentation/admin-guide/kdump/vmcoreinfo.rst | 5 +++++
 kernel/crash_core.c                            | 1 +
 2 files changed, 6 insertions(+)

Comments

Catalin Marinas July 2, 2020, 11 a.m. UTC | #1 
On Thu, May 14, 2020 at 12:22:36AM +0530, Bhupesh Sharma wrote:
> 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);

I can queue this patch via the arm64 tree (together with the second one)
but I'd like an ack from the kernel/crash_core.c maintainers. They don't
seem to have been cc'ed either (only the kexec list).

Thanks.
Dave Young July 2, 2020, 12:08 p.m. UTC | #2 
Hi Catalin,
On 07/02/20 at 12:00pm, Catalin Marinas wrote:
> On Thu, May 14, 2020 at 12:22:36AM +0530, Bhupesh Sharma wrote:
> > 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);
> 
> I can queue this patch via the arm64 tree (together with the second one)
> but I'd like an ack from the kernel/crash_core.c maintainers. They don't
> seem to have been cc'ed either (only the kexec list).

For the VMCOREINFO part, I'm fine with the changes, but since I do not
understand the arm64 pieces so I would like to leave to arm64 people to
review.  If arm64 bits are good enough, feel free to add:

Acked-by: Dave Young <dyoung@redhat.com>

Thanks
Dave
Catalin Marinas July 2, 2020, 4:55 p.m. UTC | #3 
On Thu, Jul 02, 2020 at 08:08:55PM +0800, Dave Young wrote:
> Hi Catalin,
> On 07/02/20 at 12:00pm, Catalin Marinas wrote:
> > On Thu, May 14, 2020 at 12:22:36AM +0530, Bhupesh Sharma wrote:
> > > 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);
> > 
> > I can queue this patch via the arm64 tree (together with the second one)
> > but I'd like an ack from the kernel/crash_core.c maintainers. They don't
> > seem to have been cc'ed either (only the kexec list).
> 
> For the VMCOREINFO part, I'm fine with the changes, but since I do not
> understand the arm64 pieces so I would like to leave to arm64 people to
> review.  If arm64 bits are good enough, feel free to add:
> 
> Acked-by: Dave Young <dyoung@redhat.com>

Thanks.
diff mbox series

Patch

diff --git a/Documentation/admin-guide/kdump/vmcoreinfo.rst b/Documentation/admin-guide/kdump/vmcoreinfo.rst
index e4ee8b2db604..2a632020f809 100644
--- a/Documentation/admin-guide/kdump/vmcoreinfo.rst
+++ b/Documentation/admin-guide/kdump/vmcoreinfo.rst
@@ -93,6 +93,11 @@  It exists in the sparse memory mapping model, and it is also somewhat
 similar to the mem_map variable, both of them are used to translate an
 address.
 
+MAX_PHYSMEM_BITS
+----------------
+
+Defines the maximum supported physical address space memory.
+
 page
 ----
 
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);