[Crash-utility] [PATCH] arm64: Use VA_BITS for page_offset calculation

[HAGIO KAZUHITO(萩尾 一仁)]

-----Original Message-----
> On Wed, Oct 27, 2021 at 11:17 AM HAGIO KAZUHITO(萩尾　一仁) <k-hagio-ab at nec.com <mailto:k-hagio-ab at nec.com>
> > wrote:
> 
> 
> 	Hi Pingfan, Lianbo,
> 
> 	-----Original Message-----
> 	> On Mon, Oct 25, 2021 at 4:43 PM HAGIO KAZUHITO(萩尾　一仁)
> 	> <k-hagio-ab at nec.com <mailto:k-hagio-ab at nec.com> > wrote:
> 	> >
> 	> > Hi,
> 	> >
> 	> > Here is a patch for the issue reported by Ankur.
> 	> > Could you help test this with your ramdumps and arm64 machines?
> 	> >
> 	> The patch looks good to me. And I will schedule a machine to have a test.
> 
> 	Pingfan, thank you for the check and test, it's very helpful.
> 
> 	Ankur told me that the patch was working fine.
> 
> 	Lianbo, my understanding is that to get a raw ramdump, hardware functionality
> 
> 
> 
> I mean that the raw dumpfile had been generated on my machine, but it didn't reproduce
> this issue.  :-)

oh ok, I misread your email..  Thanks for the test and ack.

Kazu

> I guess that may be related to the  kernel '.config'.
> 
> 
> 	or something is required.  But maybe you can reproduce a similar situation
> 	with QEMU memory dump without vmcoreinfo?  e.g. on RHEL:
> 
> 	  # virsh dump <domain> domain.dump --memory-only
> 
> 
> 
> 
> Thank you for the suggestion, Kazu.
> 
> 
> 	but you may need a kernel configured with VA_BITS=48 to reproduce and check
> 	the fix, I guess.
> 
> 
> 
> I can confirm that kernel has enabled the VA_BITS=48 as below:
> CONFIG_ARM64_VA_BITS_48=y
> CONFIG_ARM64_VA_BITS=48
> Thanks.
> 
> 
> 
> 	Thanks,
> 	Kazu
> 
> 	>
> 	> Regards,
> 	> Pingfan
> 	> > --
> 	> > From 028ddf655c847c16cce23198017d2ff0169bb4de Mon Sep 17 00:00:00 2001
> 	> > From: Kazuhito Hagio <k-hagio-ab at nec.com <mailto:k-hagio-ab at nec.com> >
> 	> > Date: Mon, 25 Oct 2021 16:53:26 +0900
> 	> > Subject: [PATCH] arm64: Use VA_BITS for page_offset calculation
> 	> >
> 	> > Commit 167d37e347fe ("arm64: assign page_offset with VA_BITS kernel
> 	> > configuration value") changed the page_offset calculation from
> 	> > using VA_BITS_ACTUAL to CONFIG_ARM64_VA_BITS.  This caused an error
> 	> > for ramdumps without vmcoreinfo like this:
> 	> >
> 	> >   crash: vmlinux and /var/tmp/ramdump_elf_XUtCMT do not match!
> 	> >
> 	> > Set the vmcoreinfo value to VA_BITS if available, and use VA_BITS
> 	> > for page_offset calculation instead.
> 	> >
> 	> > Also remove ARM64_FLIP_PAGE_OFFSET_ACTUAL because it's not used
> 	> > actually.
> 	> >
> 	> > Reported-by: Ankur Bansal <er.ankurbansal at gmail.com <mailto:er.ankurbansal at gmail.com> >
> 	> > Signed-off-by: Kazuhito Hagio <k-hagio-ab at nec.com <mailto:k-hagio-ab at nec.com> >
> 	> > ---
> 	> >  arm64.c | 5 ++++-
> 	> >  defs.h  | 4 +---
> 	> >  2 files changed, 5 insertions(+), 4 deletions(-)
> 	> >
> 	> > diff --git a/arm64.c b/arm64.c
> 	> > index 7069312671cf..3dcbcc642fda 100644
> 	> > --- a/arm64.c
> 	> > +++ b/arm64.c
> 	> > @@ -404,7 +404,7 @@ arm64_init(int when)
> 	> >                                 fprintf(fp, "CONFIG_ARM64_VA_BITS: %ld\n",
> ms->CONFIG_ARM64_VA_BITS);
> 	> >                                 fprintf(fp, "      VA_BITS_ACTUAL: %ld\n",
> ms->VA_BITS_ACTUAL);
> 	> >                                 fprintf(fp, "(calculated) VA_BITS: %ld\n", ms->VA_BITS);
> 	> > -                               fprintf(fp, " PAGE_OFFSET: %lx\n",
> ARM64_FLIP_PAGE_OFFSET_ACTUAL);
> 	> > +                               fprintf(fp, " PAGE_OFFSET: %lx\n", ARM64_FLIP_PAGE_OFFSET);
> 	> >                                 fprintf(fp, "    VA_START: %lx\n", ms->VA_START);
> 	> >                                 fprintf(fp, "     modules: %lx - %lx\n", ms->modules_vaddr,
> 	> ms->modules_end);
> 	> >                                 fprintf(fp, "     vmalloc: %lx - %lx\n",
> ms->vmalloc_start_addr,
> 	> ms->vmalloc_end);
> 	> > @@ -4031,6 +4031,9 @@ arm64_calc_VA_BITS(void)
> 	> >                                 error(FATAL, "cannot determine VA_BITS_ACTUAL\n");
> 	> >                 }
> 	> >
> 	> > +               if (machdep->machspec->CONFIG_ARM64_VA_BITS)
> 	> > +                       machdep->machspec->VA_BITS = machdep->machspec->CONFIG_ARM64_VA_BITS;
> 	> > +
> 	> >                 /*
> 	> >                  * The mm flip commit is introduced before 52-bits VA, which is before the
> 	> >                  * commit to export NUMBER(TCR_EL1_T1SZ)
> 	> > diff --git a/defs.h b/defs.h
> 	> > index 8b356d5e8959..971005596506 100644
> 	> > --- a/defs.h
> 	> > +++ b/defs.h
> 	> > @@ -3238,9 +3238,7 @@ typedef signed int s32;
> 	> >  #define ARM64_PAGE_OFFSET    ((0xffffffffffffffffUL) \
> 	> >                                         << (machdep->machspec->VA_BITS - 1))
> 	> >  /* kernels >= v5.4 the kernel VA space is flipped */
> 	> > -#define ARM64_FLIP_PAGE_OFFSET (-(1UL) << machdep->machspec->CONFIG_ARM64_VA_BITS)
> 	> > -#define ARM64_FLIP_PAGE_OFFSET_ACTUAL ((0xffffffffffffffffUL) \
> 	> > -                                       - ((1UL) << machdep->machspec->VA_BITS_ACTUAL) + 1)
> 	> > +#define ARM64_FLIP_PAGE_OFFSET (-(1UL) << machdep->machspec->VA_BITS)
> 	> >
> 	> >  #define ARM64_USERSPACE_TOP  ((1UL) << machdep->machspec->VA_BITS)
> 	> >  #define ARM64_USERSPACE_TOP_ACTUAL  ((1UL) << machdep->machspec->VA_BITS_ACTUAL)
> 	> > --
> 	> > 2.27.0
> 	> >
>