[PATCH] powerpc/64s: relocation, register save fixes for system reset interrupt
Mahesh J Salgaonkar
mahesh at linux.vnet.ibm.com
Wed Nov 2 19:24:43 AEDT 2016
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.
>
> Thanks,
> Nick
>
> ---
> arch/powerpc/include/asm/exception-64s.h | 13 +++++++++++--
> arch/powerpc/kernel/exceptions-64s.S | 11 ++++++++---
> 2 files changed, 19 insertions(+), 5 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/exception-64s.h b/arch/powerpc/include/asm/exception-64s.h
> index 84d49b1..3ce4366 100644
> --- a/arch/powerpc/include/asm/exception-64s.h
> +++ b/arch/powerpc/include/asm/exception-64s.h
> @@ -158,14 +158,17 @@ BEGIN_FTR_SECTION_NESTED(943) \
> std ra,offset(r13); \
> END_FTR_SECTION_NESTED(ftr,ftr,943)
>
> -#define EXCEPTION_PROLOG_0(area) \
> - GET_PACA(r13); \
> +#define EXCEPTION_PROLOG_0_PACA(area) \
> std r9,area+EX_R9(r13); /* save r9 */ \
> OPT_GET_SPR(r9, SPRN_PPR, CPU_FTR_HAS_PPR); \
> HMT_MEDIUM; \
> std r10,area+EX_R10(r13); /* save r10 - r12 */ \
> OPT_GET_SPR(r10, SPRN_CFAR, CPU_FTR_CFAR)
>
> +#define EXCEPTION_PROLOG_0(area) \
> + GET_PACA(r13); \
> + EXCEPTION_PROLOG_0_PACA(area)
> +
> #define __EXCEPTION_PROLOG_1(area, extra, vec) \
> OPT_SAVE_REG_TO_PACA(area+EX_PPR, r9, CPU_FTR_HAS_PPR); \
> OPT_SAVE_REG_TO_PACA(area+EX_CFAR, r10, CPU_FTR_CFAR); \
> @@ -196,6 +199,12 @@ END_FTR_SECTION_NESTED(ftr,ftr,943)
> EXCEPTION_PROLOG_1(area, extra, vec); \
> EXCEPTION_PROLOG_PSERIES_1(label, h);
>
> +/* Have the PACA in r13 already */
> +#define EXCEPTION_PROLOG_PSERIES_PACA(area, label, h, extra, vec) \
> + EXCEPTION_PROLOG_0_PACA(area); \
> + EXCEPTION_PROLOG_1(area, extra, vec); \
> + EXCEPTION_PROLOG_PSERIES_1(label, h);
> +
> #define __KVMTEST(h, n) \
> lbz r10,HSTATE_IN_GUEST(r13); \
> cmpwi r10,0; \
> diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
> index 08ba447..1ba82ea 100644
> --- a/arch/powerpc/kernel/exceptions-64s.S
> +++ b/arch/powerpc/kernel/exceptions-64s.S
> @@ -116,7 +116,9 @@ EXC_VIRT_NONE(0x4000, 0x4100)
>
> EXC_REAL_BEGIN(system_reset, 0x100, 0x200)
> SET_SCRATCH0(r13)
> - EXCEPTION_PROLOG_PSERIES(PACA_EXGEN, system_reset_common, EXC_STD,
> + GET_PACA(r13)
> + clrrdi r13,r13,1 /* Last bit of HSPRG0 is set if waking from winkle */
> + EXCEPTION_PROLOG_PSERIES_PACA(PACA_EXGEN, system_reset_common, EXC_STD,
> IDLETEST, 0x100)
>
> EXC_REAL_END(system_reset, 0x100, 0x200)
> @@ -124,6 +126,9 @@ EXC_VIRT_NONE(0x4100, 0x4200)
>
> #ifdef CONFIG_PPC_P7_NAP
> EXC_COMMON_BEGIN(system_reset_idle_common)
> +BEGIN_FTR_SECTION
> + GET_PACA(r13) /* Restore HSPRG0 to get the winkle bit in r13 */
> +END_FTR_SECTION_IFCLR(CPU_FTR_ARCH_300)
> bl pnv_restore_hyp_resource
>
> li r0,PNV_THREAD_RUNNING
> @@ -169,7 +174,7 @@ EXC_REAL_BEGIN(machine_check, 0x200, 0x300)
> SET_SCRATCH0(r13) /* save r13 */
> /*
> * Running native on arch 2.06 or later, we may wakeup from winkle
> - * inside machine check. If yes, then last bit of HSPGR0 would be set
> + * inside machine check. If yes, then last bit of HSPRG0 would be set
> * to 1. Hence clear it unconditionally.
> */
> GET_PACA(r13)
> @@ -388,7 +393,7 @@ EXC_COMMON_BEGIN(machine_check_handle_early)
> /*
> * Go back to winkle. Please note that this thread was woken up in
> * machine check from winkle and have not restored the per-subcore
> - * state. Hence before going back to winkle, set last bit of HSPGR0
> + * state. Hence before going back to winkle, set last bit of HSPRG0
> * to 1. This will make sure that if this thread gets woken up
> * again at reset vector 0x100 then it will get chance to restore
> * the subcore state.
> --
> 2.9.3
>
--
Mahesh J Salgaonkar
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