Re: [PATCH for-6.2 14/43] target/sparc: Set fault address in sparc_cpu_do_unaligned_access

[Peter Maydell]

On Sun, 1 Aug 2021 at 16:56, Mark Cave-Ayland
<mark.cave-ayland@ilande.co.uk> wrote:
>
> On 29/07/2021 15:51, Peter Maydell wrote:
>
> > On Thu, 29 Jul 2021 at 02:01, Richard Henderson
> > <richard.henderson@linaro.org> wrote:
> >>
> >> We ought to have been recording the virtual address for reporting
> >> to the guest trap handler.  Mirror the SFSR FIXME from the sparc64
> >> version of get_physical_address_data.
> >>
> >> Cc: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
> >> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> >> ---
> >>   target/sparc/ldst_helper.c | 8 ++++++++
> >>   1 file changed, 8 insertions(+)
> >>
> >> diff --git a/target/sparc/ldst_helper.c b/target/sparc/ldst_helper.c
> >> index 974afea041..7367b48c8b 100644
> >> --- a/target/sparc/ldst_helper.c
> >> +++ b/target/sparc/ldst_helper.c
> >> @@ -1963,6 +1963,14 @@ void QEMU_NORETURN 
> >> sparc_cpu_do_unaligned_access(CPUState *cs, vaddr addr,
> >>       SPARCCPU *cpu = SPARC_CPU(cs);
> >>       CPUSPARCState *env = &cpu->env;
> >>
> >> +#ifdef TARGET_SPARC64
> >> +    /* FIXME: ASI field in SFSR must be set */
> >> +    env->dmmu.sfsr = SFSR_VALID_BIT; /* Fault status register */
> >> +    env->dmmu.sfar = addr;           /* Fault address register */
> >> +#else
> >> +    env->mmuregs[4] = addr;
> >> +#endif
> >> +
> >>       cpu_raise_exception_ra(env, TT_UNALIGNED, retaddr);
> >>   }
> >>   #endif
> >
> > The architecture manual seems to be gratuitously opaque about
> > whether and where the fault address for an alignment fault gets
> > recorded, but Linux at least for 64-bit seems to pull it out of the
> > sfar, so I guess that's right.
>
> Yeah, this part is actually contained within the UltraSPARC II specification 
> - it can
> be found in section 6.4 "MMU-Related Faults and Traps" table 6-3 which 
> indicates that
> for *_mem_address_not_aligned traps the D-SFSR and SFAR registers within the 
> MMU are
> updated.

Do you know what 32-bit CPUs do? The Linux kernel sources don't help
here because they don't bother to report the fault address...

thanks
-- PMM