On Fri, 2023-07-28 at 13:02 -0700, Richard Henderson wrote:
> On 7/28/23 12:55, Richard Henderson wrote:
> > This solves a problem in which the store to LowCore during tlb_fill
> > triggers a clean-page TB invalidation for page0 during translation,
> > which results in an assertion failure for locked pages.
> >
> > By delaying the store until after the exception has been raised,
> > we will have unwound the pages locked for translation and the
> > problem does not arise. There are plenty of other updates to
> > LowCore while delivering an interrupt/exception; trans_exc_code
> > does not need to be special.
> >
> > Reported-by: Claudio Fontana <cfont...@suse.de>
> > Signed-off-by: Richard Henderson <richard.hender...@linaro.org>
> > ---
> > target/s390x/tcg/excp_helper.c | 42 +++++++++++++++++++++++------
> > -----
> > 1 file changed, 29 insertions(+), 13 deletions(-)
[...]
> > switch (env->int_pgm_code) {
> > case PGM_PER:
> > - if (env->per_perc_atmid & PER_CODE_EVENT_NULLIFICATION) {
> > - break;
> > - }
> > - /* FALL THROUGH */
> > + advance = !(env->per_perc_atmid &
> > PER_CODE_EVENT_NULLIFICATION);
> > + break;
> > + case PGM_ASCE_TYPE:
> > + case PGM_REG_FIRST_TRANS:
> > + case PGM_REG_SEC_TRANS:
> > + case PGM_REG_THIRD_TRANS:
> > + case PGM_SEGMENT_TRANS:
> > + case PGM_PAGE_TRANS:
> > + assert(env->int_pgm_code == env->tlb_fill_exc);
> > + set_trans_exc_code = true;
> > + break;
>
> I should have mentioned that this block of exceptions came from page
> 3-76
> (Translation-Exception Identification for DAT Exceptions) of the 13th
> edition of the PoO.
>
> > + case PGM_PROTECTION:
> > + case PGM_TRANS_SPEC:
> > + assert(env->int_pgm_code == env->tlb_fill_exc);
> > + set_trans_exc_code = true;
> > + advance = true;
> > + break;
>
> These exceptions came from seeing an early kernel fault, grepping for
> the set of
> exceptions raised in mmu_helper.c, and eliminating PGM_ADDRESSING per
> the first hunk.
Does POp specify that the CPU stores Translation-Exception
Identification on Translation-Specification Exceptions
(PGM_TRANS_SPEC)? I re-read the 0xA8 documentation a few times, but
could not find it.
It's also interesting what the kernel was attempting when it got
PGM_TRANS_SPEC and recovered from it. Maybe something else is wrong?
Other than the POp question:
Reviewed-by: Ilya Leoshkevich <i...@linux.ibm.com>
>
> I wasn't sure where to look for the full specification of exception
> effects, but this did
> solve the kernel fault.
>
>
> r~
