Re: PowerNV decrementer fails to fire

[Anton Blanchard]

Hi Cédric,

> I could reproduce but I had to set HILE in HDI0 to make progress. 
> The test program misses a : 
> 
>       /* HID0: HILE */
>       LOAD_IMM64(r0, 0x800000000000000)
>       mtspr   0x3f0,r0
> 
> If I am correct.

Oops, yes you are right - we had a local HILE hack that we forgot
about.

> With a quick hack, QEMU generated the expected DECR exception but 
> it's ugly and incomplete. The emulation of the mtmsrd instruction 
> requires more care. The L=1 form needs a rework to handle pending 
> interrupts and we need to modify the MSR store helper also to return 
> the highest exception.

Thanks for looking into it!

Anton

> 
> Thanks,
> 
> C. 
> 
> > 
> > Thanks,
> > Anton
> > --
> > 
> > #include <ppc-asm.h>
> > 
> > /* Load an immediate 64-bit value into a register */
> > #define LOAD_IMM64(r, e)                    \
> >     lis     r,(e)@highest;                  \
> >     ori     r,r,(e)@higher;                 \
> >     rldicr  r,r, 32, 31;                    \
> >     oris    r,r, (e)@h;                     \
> >     ori     r,r, (e)@l;
> > 
> > #define FIXUP_ENDIAN
> >    \ tdi   0,0,0x48;          /* Reverse endian of b . + 8
> >     */ \ b     191f;          /* Skip trampoline if endian is
> > good        */ \ .long 0xa600607d; /* mfmsr r11
> >             */ \ .long 0x01006b69; /* xori r11,r11,1
> >             */ \ .long 0x05009f42; /* bcl 20,31,$+4
> >             */ \ .long 0xa602487d; /* mflr r10
> >             */ \ .long 0x14004a39; /* addi r10,r10,20
> >             */ \ .long 0xa64b5a7d; /* mthsrr0 r10
> >             */ \ .long 0xa64b7b7d; /* mthsrr1 r11
> >             */ \ .long 0x2402004c; /* hrfid
> >             */ \ 191:
> > 
> >     .= 0x0
> > .globl _start
> > _start:
> >     b       1f
> > 
> >     .= 0x10
> >     FIXUP_ENDIAN
> >     b       1f
> > 
> >     .= 0x100
> > 1:
> >     FIXUP_ENDIAN
> >     b       __initialize
> > 
> > #define EXCEPTION(nr)               \
> >     .= nr                   ;\
> >     b       .
> > 
> >     /* More exception stubs */
> >     EXCEPTION(0x300)
> >     EXCEPTION(0x380)
> >     EXCEPTION(0x400)
> >     EXCEPTION(0x480)
> >     EXCEPTION(0x500)
> >     EXCEPTION(0x600)
> >     EXCEPTION(0x700)
> >     EXCEPTION(0x800)
> > 
> >     .= 0x900
> >     LOAD_IMM64(r0, 0x1000000)
> >     mtdec   r0
> >     addi    r31,r31,1
> >     rfid
> > 
> >     EXCEPTION(0x980)
> >     EXCEPTION(0xa00)
> >     EXCEPTION(0xb00)
> >     EXCEPTION(0xc00)
> >     EXCEPTION(0xd00)
> >     EXCEPTION(0xe00)
> >     EXCEPTION(0xe20)
> >     EXCEPTION(0xe40)
> >     EXCEPTION(0xe60)
> >     EXCEPTION(0xe80)
> >     EXCEPTION(0xf00)
> >     EXCEPTION(0xf20)
> >     EXCEPTION(0xf40)
> >     EXCEPTION(0xf60)
> >     EXCEPTION(0xf80)
> >     EXCEPTION(0x1000)
> >     EXCEPTION(0x1100)
> >     EXCEPTION(0x1200)
> >     EXCEPTION(0x1300)
> >     EXCEPTION(0x1400)
> >     EXCEPTION(0x1500)
> >     EXCEPTION(0x1600)
> > 
> > __initialize:
> >     /* SF, HV, EE, RI, LE */
> >     LOAD_IMM64(r0, 0x9000000000008003)
> >     mtmsrd  r0
> > 
> >     LOAD_IMM64(r0, 0x1000000)
> >     mtdec r0
> > 
> > 1:  LOAD_IMM64(r30,0x8000)
> >     mtmsrd  r30,1
> > 
> >     /* We should take the decrementer here */
> > #ifdef FIX_BROKEN
> >     LOAD_IMM64(r29,0x100000000)
> >     mtctr   r29
> > 2:  bdnz    2b
> > #endif
> > 
> >     li      r30,0x0
> >     mtmsrd  r30,1
> >     b       1b
> >   
>