On Thu Mar 23, 2023 at 10:12 PM AEST, Thomas Huth wrote: > On 20/03/2023 08.03, Nicholas Piggin wrote: > > This consolidates several implementations, and it no longer leaves > > MSR[EE] enabled after the decrementer interrupt is handled, but > > rather disables it on return. > > > > The handler no longer allows a continuous ticking, but rather dec > > has to be re-armed and EE re-enabled (e.g., via H_CEDE hcall) each > > time. > > > > Signed-off-by: Nicholas Piggin <npig...@gmail.com> > > --- > > lib/powerpc/asm/handlers.h | 2 +- > > lib/powerpc/asm/ppc_asm.h | 1 + > > lib/powerpc/asm/processor.h | 7 +++++++ > > lib/powerpc/handlers.c | 10 ++++----- > > lib/powerpc/processor.c | 42 +++++++++++++++++++++++++++++++++++++ > > powerpc/sprs.c | 6 +----- > > powerpc/tm.c | 20 +----------------- > > 7 files changed, 57 insertions(+), 31 deletions(-) > > > > diff --git a/lib/powerpc/asm/handlers.h b/lib/powerpc/asm/handlers.h > > index 64ba727..e4a0cd4 100644 > > --- a/lib/powerpc/asm/handlers.h > > +++ b/lib/powerpc/asm/handlers.h > > @@ -3,6 +3,6 @@ > > > > #include <asm/ptrace.h> > > > > -void dec_except_handler(struct pt_regs *regs, void *data); > > +void dec_handler_oneshot(struct pt_regs *regs, void *data); > > > > #endif /* _ASMPOWERPC_HANDLERS_H_ */ > > diff --git a/lib/powerpc/asm/ppc_asm.h b/lib/powerpc/asm/ppc_asm.h > > index 1b85f6b..6299ff5 100644 > > --- a/lib/powerpc/asm/ppc_asm.h > > +++ b/lib/powerpc/asm/ppc_asm.h > > @@ -36,6 +36,7 @@ > > #endif /* __BYTE_ORDER__ */ > > > > /* Machine State Register definitions: */ > > +#define MSR_EE_BIT 15 /* External Interrupts Enable */ > > #define MSR_SF_BIT 63 /* 64-bit mode */ > > > > #endif /* _ASMPOWERPC_PPC_ASM_H */ > > diff --git a/lib/powerpc/asm/processor.h b/lib/powerpc/asm/processor.h > > index ac001e1..ebfeff2 100644 > > --- a/lib/powerpc/asm/processor.h > > +++ b/lib/powerpc/asm/processor.h > > @@ -20,6 +20,8 @@ static inline uint64_t get_tb(void) > > > > extern void delay(uint64_t cycles); > > extern void udelay(uint64_t us); > > +extern void sleep_tb(uint64_t cycles); > > +extern void usleep(uint64_t us); > > > > static inline void mdelay(uint64_t ms) > > { > > @@ -27,4 +29,9 @@ static inline void mdelay(uint64_t ms) > > udelay(1000); > > } > > > > +static inline void msleep(uint64_t ms) > > +{ > > + usleep(ms * 1000); > > +} > > + > > #endif /* _ASMPOWERPC_PROCESSOR_H_ */ > > diff --git a/lib/powerpc/handlers.c b/lib/powerpc/handlers.c > > index c8721e0..296f14f 100644 > > --- a/lib/powerpc/handlers.c > > +++ b/lib/powerpc/handlers.c > > @@ -9,15 +9,13 @@ > > #include <libcflat.h> > > #include <asm/handlers.h> > > #include <asm/ptrace.h> > > +#include <asm/ppc_asm.h> > > > > /* > > * Generic handler for decrementer exceptions (0x900) > > - * Just reset the decrementer back to the value specified when registering > > the > > - * handler > > + * Return with MSR[EE] disabled. > > */ > > -void dec_except_handler(struct pt_regs *regs __unused, void *data) > > +void dec_handler_oneshot(struct pt_regs *regs, void *data) > > { > > - uint64_t dec = *((uint64_t *) data); > > - > > - asm volatile ("mtdec %0" : : "r" (dec)); > > + regs->msr &= ~(1UL << MSR_EE_BIT); > > } > > diff --git a/lib/powerpc/processor.c b/lib/powerpc/processor.c > > index ec85b9d..e77a240 100644 > > --- a/lib/powerpc/processor.c > > +++ b/lib/powerpc/processor.c > > @@ -10,6 +10,8 @@ > > #include <asm/ptrace.h> > > #include <asm/setup.h> > > #include <asm/barrier.h> > > +#include <asm/hcall.h> > > +#include <asm/handlers.h> > > > > static struct { > > void (*func)(struct pt_regs *, void *data); > > @@ -54,3 +56,43 @@ void udelay(uint64_t us) > > { > > delay((us * tb_hz) / 1000000); > > } > > + > > +void sleep_tb(uint64_t cycles) > > +{ > > + uint64_t start, end, now; > > + > > + start = now = get_tb(); > > + end = start + cycles; > > + > > + while (end > now) { > > + uint64_t left = end - now; > > + > > + /* Could support large decrementer */ > > + if (left > 0x7fffffff) > > + left = 0x7fffffff; > > + > > + asm volatile ("mtdec %0" : : "r" (left)); > > + handle_exception(0x900, &dec_handler_oneshot, NULL); > > Wouldn't it be better to first call handle_exception() before moving > something into the decrementer?
It shouldn't really matter, the drecrementer could be anything here (probably it's already -ve here if it starts at zero). It only matters when MSR[EE]=1 or we make the H_CEDE call. I'll add a comment at least. Thanks, Nick