On 09/09/2012 09:24 PM, Benjamin Herrenschmidt wrote: > On Sun, 2012-09-09 at 04:43 -0700, Haren Myneni wrote: >> Several macros are defined for saving and restore user defined PPR value. >> >> Signed-off-by: Haren Myneni <ha...@us.ibm.com> >> --- >> arch/powerpc/include/asm/exception-64s.h | 35 >> ++++++++++++++++++++++++++++++ >> arch/powerpc/include/asm/reg.h | 1 + >> 2 files changed, 36 insertions(+) >> >> diff --git a/arch/powerpc/include/asm/exception-64s.h >> b/arch/powerpc/include/asm/exception-64s.h >> index bfd3f1f..618fd18 100644 >> --- a/arch/powerpc/include/asm/exception-64s.h >> +++ b/arch/powerpc/include/asm/exception-64s.h >> @@ -62,6 +62,41 @@ >> #define EXC_HV H >> #define EXC_STD >> >> +/* >> + * PPR save/restore macros - Used on P7 or later processors >> + */ >> +#define SAVE_PPR(area, ra, rb) >> \ >> +BEGIN_FTR_SECTION_NESTED(940) >> \ >> + ld ra,area+EX_PPR(r13); /* Read PPR from paca */ \ >> + clrrdi rb,r1,THREAD_SHIFT; /* thread_info struct */ \ >> + std ra,TI_PPR(rb); /* Save PPR in thread_info */ \ >> +END_FTR_SECTION_NESTED(CPU_FTR_HAS_PPR,CPU_FTR_HAS_PPR,940) > > Why the thread info and not the thread struct ?
We can also use thread struct, but the saved ppr is needed as long as the process is in kernel context. Once the process exits, we do not need this value - means the kernel or any other command will not be reading this value. Even the process can change this value later. Need to add ppr in thread_struct which uses extra 8 bytes for each task. Whereas thread_info is at the top of stack. No need to allocate extra memory. Since the saved process PPR value is needed temporarily whenever the process is in kernel, thought thread_info is proper. Also easy to read - one less load instruction. Saving in thread_info: ld r4,area+EX_PPR(r13); clrrdi r5,r1,THREAD_SHIFT; std r4,TI_PPR(r5); Saving in thread_struct: ld r4,PACACURRENT(r13) addi r5,r4,THREAD ld r4,paca+EX_PPR(r13); std r4,THREAD_PPR(r5) If you prefer thread_struct, I will change the patch. Please let me know. Thanks Haren > > Cheers, > Ben. > >> +#define RESTORE_PPR(ra,rb) \ >> +BEGIN_FTR_SECTION_NESTED(941) >> \ >> + clrrdi ra,r1,THREAD_SHIFT; \ >> + ld rb,TI_PPR(ra); /* Read PPR from thread_info */ \ >> + mtspr SPRN_PPR,rb; /* Restore PPR */ \ >> +END_FTR_SECTION_NESTED(CPU_FTR_HAS_PPR,CPU_FTR_HAS_PPR,941) >> + >> +#define RESTORE_PPR_PACA(area,ra) \ >> +BEGIN_FTR_SECTION_NESTED(942) >> \ >> + ld ra,area+EX_PPR(r13); \ >> + mtspr SPRN_PPR,ra; \ >> +END_FTR_SECTION_NESTED(CPU_FTR_HAS_PPR,CPU_FTR_HAS_PPR,942) >> + >> +#define HMT_MEDIUM_NO_PPR \ >> +BEGIN_FTR_SECTION_NESTED(944) >> \ >> + HMT_MEDIUM; \ >> +END_FTR_SECTION_NESTED(CPU_FTR_HAS_PPR,0,944) /*non P7*/ >> + >> +#define HMT_MEDIUM_HAS_PPR(area, ra) >> \ >> +BEGIN_FTR_SECTION_NESTED(943) >> \ >> + mfspr ra,SPRN_PPR; \ >> + std ra,area+EX_PPR(r13); \ >> + HMT_MEDIUM; \ >> +END_FTR_SECTION_NESTED(CPU_FTR_HAS_PPR,CPU_FTR_HAS_PPR,943) /* P7 */ >> + >> #define __EXCEPTION_PROLOG_1(area, extra, vec) >> \ >> GET_PACA(r13); \ >> std r9,area+EX_R9(r13); /* save r9 - r12 */ \ >> diff --git a/arch/powerpc/include/asm/reg.h b/arch/powerpc/include/asm/reg.h >> index 6386086..dff2f89 100644 >> --- a/arch/powerpc/include/asm/reg.h >> +++ b/arch/powerpc/include/asm/reg.h >> @@ -284,6 +284,7 @@ >> #define SPRN_DBAT6U 0x23C /* Data BAT 6 Upper Register */ >> #define SPRN_DBAT7L 0x23F /* Data BAT 7 Lower Register */ >> #define SPRN_DBAT7U 0x23E /* Data BAT 7 Upper Register */ >> +#define SPRN_PPR 0x380 /* SMT Thread status Register */ >> >> #define SPRN_DEC 0x016 /* Decrement Register */ >> #define SPRN_DER 0x095 /* Debug Enable Regsiter */ > > _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
