On Mon, May 31, 2021 at 4:40 PM HAGIO KAZUHITO(萩尾 一仁)
<k-hagio-ab@xxxxxxx> wrote:
>
>
> -----Original Message-----
> > On RHEL9, crash hits a bug when executing "crash /proc/kcore" :
> > seek error: kernel virtual address: ffff6a0f3fff0000 type: "pmd page"
> >
> > The kernel virtual address does not vary with va_actual bits, instead,
> > is determined by configuration value. But crash does not observe this
> > fact.
> >
> > Since this disagreement only happens if 52-bits kernel on 48 bits platform,
> > it can be handled only if "phys_offset_nominal < 0".
> >
> > Signed-off-by: Pingfan Liu <piliu@xxxxxxxxxx>
> > Cc: HAGIO KAZUHITO <k-hagio-ab@xxxxxxx>
> > Cc: Lianbo Jiang <lijiang@xxxxxxxxxx>
> > Cc: Bhupesh Sharma <bhupesh.sharma@xxxxxxxxxx>
> > To: crash-utility@xxxxxxxxxx
> > ---
> > arm64.c | 10 +++++++++-
> > defs.h | 1 +
> > 2 files changed, 10 insertions(+), 1 deletion(-)
> >
> > diff --git a/arm64.c b/arm64.c
> > index f1bac84..7cc19e8 100644
> > --- a/arm64.c
> > +++ b/arm64.c
> > @@ -221,7 +221,15 @@ arm64_init(int when)
> > arm64_calc_VA_BITS();
> > arm64_calc_KERNELPACMASK();
> > ms = machdep->machspec;
> > - if (ms->VA_BITS_ACTUAL) {
> > + /* For 52-bits kernel running on 48 bits platform */
> > + if (ms->phys_offset_nominal < 0) {
>
> Maybe I miss something, is the ms->phys_offset_nominal set at this point?
>
You are right. And I am planning to use ms->VA_BITS_ACTUAL as the hint
of memory layout flip since vabits_actual comes after the memory
layout flip commit.
Thanks,
Pingfan
> if (ms->phys_offset_nominal < 0) {
> ...
> /* use machdep parameters */
> arm64_calc_phys_offset(); <<-- set here?
> arm64_calc_physvirt_offset();
>
> Thanks,
> Kazu
>
> > + ms->page_offset = ARM64_FLIP_PAGE_OFFSET;
> > + /* useless on arm64 */
> > + machdep->identity_map_base = ARM64_FLIP_PAGE_OFFSET;
> > + machdep->kvbase = ARM64_FLIP_PAGE_OFFSET;
> > + ms->userspace_top = ARM64_USERSPACE_TOP_ACTUAL;
> > + /* For 52-bits on 52-bits platform, or 48-bits on 48 */
> > + } else if (ms->VA_BITS_ACTUAL) {
> > ms->page_offset = ARM64_FLIP_PAGE_OFFSET_ACTUAL;
> > machdep->identity_map_base = ARM64_FLIP_PAGE_OFFSET_ACTUAL;
> > machdep->kvbase = ARM64_FLIP_PAGE_OFFSET_ACTUAL;
> > diff --git a/defs.h b/defs.h
> > index 1007c69..f804212 100644
> > --- a/defs.h
> > +++ b/defs.h
> > @@ -3224,6 +3224,7 @@ 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)
> >
> > --
> > 2.29.2
>
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