[PATCH] powerpc/64s: relocation, register save fixes for system reset interrupt
Nicholas Piggin
npiggin at gmail.com
Wed Nov 2 19:36:24 AEDT 2016
On Wed, 2 Nov 2016 13:54:43 +0530
Mahesh J Salgaonkar <mahesh at linux.vnet.ibm.com> wrote:
> On 2016-11-02 17:57:01 Wed, Nicholas Piggin wrote:
> > On Wed, 2 Nov 2016 11:34:59 +0530
> > Mahesh Jagannath Salgaonkar <mahesh at linux.vnet.ibm.com> wrote:
> >
> > > On 10/13/2016 07:47 AM, Nicholas Piggin wrote:
> > > > This patch does a couple of things. First of all, powernv immediately
> > > > explodes when running a relocated kernel, because the system reset
> > > > exception for handling sleeps does not do correct relocated branches.
> > > >
> > > > Secondly, the sleep handling code trashes the condition and cfar
> > > > registers, which we would like to preserve for debugging purposes (for
> > > > non-sleep case exception).
> > > >
> > > > This patch changes the exception to use the standard format that saves
> > > > registers before any tests or branches are made. It adds the test for
> > > > idle-wakeup as an "extra" to break out of the normal exception path.
> > > > Then it branches to a relocated idle handler that calls the various
> > > > idle handling functions.
> > > >
> > > > After this patch, POWER8 CPU simulator now boots powernv kernel that is
> > > > running at non-zero.
> > > >
> > > > Cc: Balbir Singh <bsingharora at gmail.com>
> > > > Cc: Shreyas B. Prabhu <shreyas at linux.vnet.ibm.com>
> > > > Cc: Gautham R. Shenoy <ego at linux.vnet.ibm.com>
> > > > Signed-off-by: Nicholas Piggin <npiggin at gmail.com>
> > > > ---
> > > > arch/powerpc/include/asm/exception-64s.h | 16 ++++++++++
> > > > arch/powerpc/kernel/exceptions-64s.S | 50 ++++++++++++++++++--------------
> > > > 2 files changed, 45 insertions(+), 21 deletions(-)
> > > >
> > > > diff --git a/arch/powerpc/include/asm/exception-64s.h b/arch/powerpc/include/asm/exception-64s.h
> > > > index 2e4e7d8..84d49b1 100644
> > > > --- a/arch/powerpc/include/asm/exception-64s.h
> > > > +++ b/arch/powerpc/include/asm/exception-64s.h
> > > > @@ -93,6 +93,10 @@
> > > > ld reg,PACAKBASE(r13); /* get high part of &label */ \
> > > > ori reg,reg,(FIXED_SYMBOL_ABS_ADDR(label))@l;
> > > >
> > > > +#define __LOAD_HANDLER(reg, label) \
> > > > + ld reg,PACAKBASE(r13); \
> > > > + ori reg,reg,(ABS_ADDR(label))@l;
> > > > +
> > > > /* Exception register prefixes */
> > > > #define EXC_HV H
> > > > #define EXC_STD
> > > > @@ -208,6 +212,18 @@ END_FTR_SECTION_NESTED(ftr,ftr,943)
> > > > #define kvmppc_interrupt kvmppc_interrupt_pr
> > > > #endif
> > > >
> > > > +#ifdef CONFIG_RELOCATABLE
> > > > +#define BRANCH_TO_COMMON(reg, label) \
> > > > + __LOAD_HANDLER(reg, label); \
> > > > + mtctr reg; \
> > > > + bctr
> > > > +
> > > > +#else
> > > > +#define BRANCH_TO_COMMON(reg, label) \
> > > > + b label
> > > > +
> > > > +#endif
> > > > +
> > > > #define __KVM_HANDLER_PROLOG(area, n) \
> > > > BEGIN_FTR_SECTION_NESTED(947) \
> > > > ld r10,area+EX_CFAR(r13); \
> > > > diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
> > > > index 08992f8..e680e84 100644
> > > > --- a/arch/powerpc/kernel/exceptions-64s.S
> > > > +++ b/arch/powerpc/kernel/exceptions-64s.S
> > > > @@ -95,19 +95,35 @@ __start_interrupts:
> > > > /* No virt vectors corresponding with 0x0..0x100 */
> > > > EXC_VIRT_NONE(0x4000, 0x4100)
> > > >
> > > > -EXC_REAL_BEGIN(system_reset, 0x100, 0x200)
> > > > - SET_SCRATCH0(r13)
> > > > +
> > > > #ifdef CONFIG_PPC_P7_NAP
> > > > -BEGIN_FTR_SECTION
> > > > - /* Running native on arch 2.06 or later, check if we are
> > > > - * waking up from nap/sleep/winkle.
> > > > + /*
> > > > + * If running native on arch 2.06 or later, check if we are waking up
> > > > + * from nap/sleep/winkle, and branch to idle handler.
> > > > */
> > > > - mfspr r13,SPRN_SRR1
> > > > - rlwinm. r13,r13,47-31,30,31
> > > > - beq 9f
> > > > +#define IDLETEST(n) \
> > > > + BEGIN_FTR_SECTION ; \
> > > > + mfspr r10,SPRN_SRR1 ; \
> > > > + rlwinm. r10,r10,47-31,30,31 ; \
> > > > + beq- 1f ; \
> > > > + cmpwi cr3,r10,2 ; \
> > > > + BRANCH_TO_COMMON(r10, system_reset_idle_common) ; \
> > > > +1: \
> > > > + END_FTR_SECTION_IFSET(CPU_FTR_HVMODE | CPU_FTR_ARCH_206)
> > > > +#else
> > > > +#define IDLETEST NOTEST
> > > > +#endif
> > > >
> > > > - cmpwi cr3,r13,2
> > > > - GET_PACA(r13)
> > > > +EXC_REAL_BEGIN(system_reset, 0x100, 0x200)
> > > > + SET_SCRATCH0(r13)
> > > > + EXCEPTION_PROLOG_PSERIES(PACA_EXGEN, system_reset_common, EXC_STD,
> > > > + IDLETEST, 0x100)
> > >
> > > Very sorry for late review. On arch 2.07 and less if we wakeup from
> > > winkle then last bit of HSPGR0 would be set to 1. Hence before we access
> > > paca we need to fix it by clearing that bit and that is done in
> > > pnv_restore_hyp_resource(). But with this patch, we would end up there
> > > after going through EXCEPTION_PROLOG_PSERIES(). This macro gets the paca
> > > using GET_PACA(r13) and all the EXCEPTION_PROLOG_* starts
> > > using/accessing r13/paca without fixing it. Wouldn't this break things
> > > badly on arch 2.07 and less ? Am I missing anything ?
> >
> > Arg, that's a stupid bug :( Thanks for catching it.
> >
> > Would something like the following do the trick, do you think? I obviously
> > was not reaching winkle state in my testing.
>
> Yup, that will work.
Okay, I'll work with that. What's the best way to make a P8 do winkle sleeps?
Thanks,
Nick
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