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PowerNV decrementer fails to fire
From: |
Anton Blanchard |
Subject: |
PowerNV decrementer fails to fire |
Date: |
Thu, 24 Oct 2019 09:04:31 +1100 |
Hi,
Mikey and I noticed that the decrementer isn't firing when
it should. If a decrementer is pending and an mtmsrd(MSR_EE) is
executed then we should take the decrementer exception. From the PPC AS:
If MSR EE = 0 and an External, Decrementer, or Per-
formance Monitor exception is pending, executing
an mtmsrd instruction that sets MSR EE to 1 will
cause the interrupt to occur before the next instruc-
tion is executed, if no higher priority exception
exists
A test case is below. r31 is incremented for every decrementer
exception.
powerpc64le-linux-gcc -c test.S
powerpc64le-linux-ld -Ttext=0x0 -o test.elf test.o
powerpc64le-linux-objcopy -O binary test.elf test.bin
r31 never moves. If I build with:
powerpc64le-linux-gcc -DFIX_BROKEN -c test.S
I see r31 move.
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
- PowerNV decrementer fails to fire,
Anton Blanchard <=