On Thu, Jan 27, 2022 at 6:14 PM Peter Maydell <peter.mayd...@linaro.org>
wrote:
> Ping for code review? This is a nice short easy one :-)
>
Looks good comparing with the Pseudocode. I tried reading the chapters
about these exceptions but couldn't find a clear description :-)
Reviewed-by: Edgar E. Iglesias <edgar.igles...@xilinx.com>
>
> thanks
> -- PMM
>
> On Mon, 17 Jan 2022 at 13:19, Peter Maydell <peter.mayd...@linaro.org>
> wrote:
> >
> > The exception caused by an SVC instruction may be taken to AArch32
> > Hyp mode for two reasons:
> > * HCR.TGE indicates that exceptions from EL0 should trap to EL2
> > * we were already in Hyp mode
> >
> > The entrypoint in the vector table to be used differs in these two
> > cases: for an exception routed to Hyp mode from EL0, we enter at the
> > common 0x14 "hyp trap" entrypoint. For SVC from Hyp mode to Hyp
> > mode, we enter at the 0x08 (svc/hvc trap) entrypoint.
> > In the v8A Arm ARM pseudocode this is done in AArch32.TakeSVCException.
> >
> > QEMU incorrectly routed both of these exceptions to the 0x14
> > entrypoint. Correct the entrypoint for SVC from Hyp to Hyp by making
> > use of the existing logic which handles "normal entrypoint for
> > Hyp-to-Hyp, otherwise 0x14" for traps like UNDEF and data/prefetch
> > aborts (reproduced here since it's outside the visible context
> > in the diff for this commit):
> >
> > if (arm_current_el(env) != 2 && addr < 0x14) {
> > addr = 0x14;
> > }
> >
> > Signed-off-by: Peter Maydell <peter.mayd...@linaro.org>
> > ---
> > target/arm/helper.c | 4 ++--
> > 1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/target/arm/helper.c b/target/arm/helper.c
> > index cfca0f5ba6d..a898e400f6c 100644
> > --- a/target/arm/helper.c
> > +++ b/target/arm/helper.c
> > @@ -9655,7 +9655,7 @@ static void
> arm_cpu_do_interrupt_aarch32_hyp(CPUState *cs)
> > * separately here.
> > *
> > * The vector table entry used is always the 0x14 Hyp mode entry
> point,
> > - * unless this is an UNDEF/HVC/abort taken from Hyp to Hyp.
> > + * unless this is an UNDEF/SVC/HVC/abort taken from Hyp to Hyp.
> > * The offset applied to the preferred return address is always zero
> > * (see DDI0487C.a section G1.12.3).
> > * PSTATE A/I/F masks are set based only on the SCR.EA/IRQ/FIQ
> values.
> > @@ -9669,7 +9669,7 @@ static void
> arm_cpu_do_interrupt_aarch32_hyp(CPUState *cs)
> > addr = 0x04;
> > break;
> > case EXCP_SWI:
> > - addr = 0x14;
> > + addr = 0x08;
> > break;
> > case EXCP_BKPT:
> > /* Fall through to prefetch abort. */
> > --
> > 2.25.1
> >
>
>
