On POWER6 and POWER7 if the input operand to an instruction is a
denormalised single precision binary floating we can take a
denormalisation exception where it's expected that the hypervisor (HV=1)
will fix up the inputs before the instruction is run.
This adds code to handle this denormalisation exception for POWER6 and
POWER7.
It also add a CONFIG_PPC_DENORMALISATION option and sets it in
pseries/ppc64_defconfig.
This is useful on bare metal systems only. Based on patch from Milton
Miller.
Signed-off-by: Michael Neuling <mi...@neuling.org>
---
arch/powerpc/Kconfig | 7 +
arch/powerpc/configs/ppc64_defconfig | 1
arch/powerpc/configs/pseries_defconfig | 1
arch/powerpc/include/asm/ppc-opcode.h | 2
arch/powerpc/include/asm/reg.h | 1
arch/powerpc/kernel/exceptions-64s.S | 125 +++++++++++++++++++++++++++++++++
6 files changed, 137 insertions(+)
Index: linux-ozlabs/arch/powerpc/Kconfig
===================================================================
--- linux-ozlabs.orig/arch/powerpc/Kconfig
+++ linux-ozlabs/arch/powerpc/Kconfig
@@ -556,6 +556,13 @@ config SCHED_SMT
when dealing with POWER5 cpus at a cost of slightly increased
overhead in some places. If unsure say N here.
+config PPC_DENORMALISATION
+ bool "PowerPC denormalisation exception handling"
+ default "n"
+ ---help---
+ Add support for handling denormalisation of single precision
+ values. Useful for bare metal only. If unsure say Y here.
+
config CMDLINE_BOOL
bool "Default bootloader kernel arguments"
Index: linux-ozlabs/arch/powerpc/configs/ppc64_defconfig
===================================================================
--- linux-ozlabs.orig/arch/powerpc/configs/ppc64_defconfig
+++ linux-ozlabs/arch/powerpc/configs/ppc64_defconfig
@@ -54,6 +54,7 @@ CONFIG_KEXEC=y
CONFIG_IRQ_ALL_CPUS=y
CONFIG_MEMORY_HOTREMOVE=y
CONFIG_SCHED_SMT=y
+CONFIG_PPC_DENORMALISATION=y
CONFIG_PCCARD=y
CONFIG_ELECTRA_CF=y
CONFIG_HOTPLUG_PCI=m
Index: linux-ozlabs/arch/powerpc/configs/pseries_defconfig
===================================================================
--- linux-ozlabs.orig/arch/powerpc/configs/pseries_defconfig
+++ linux-ozlabs/arch/powerpc/configs/pseries_defconfig
@@ -47,6 +47,7 @@ CONFIG_MEMORY_HOTREMOVE=y
CONFIG_PPC_64K_PAGES=y
CONFIG_PPC_SUBPAGE_PROT=y
CONFIG_SCHED_SMT=y
+CONFIG_PPC_DENORMALISATION=y
CONFIG_HOTPLUG_PCI=m
CONFIG_HOTPLUG_PCI_RPA=m
CONFIG_HOTPLUG_PCI_RPA_DLPAR=m
Index: linux-ozlabs/arch/powerpc/include/asm/ppc-opcode.h
===================================================================
--- linux-ozlabs.orig/arch/powerpc/include/asm/ppc-opcode.h
+++ linux-ozlabs/arch/powerpc/include/asm/ppc-opcode.h
@@ -157,6 +157,8 @@
VSX_XX1((s), (a), (b)))
#define XXLOR(t, a, b) stringify_in_c(.long PPC_INST_XXLOR | \
VSX_XX3((t), (a), (b)))
+#define XVCPSGNDP(t, a, b) stringify_in_c(.long (0xf0000780 | \
+ VSX_XX3((t), (a), (b))))
#define PPC_NAP stringify_in_c(.long PPC_INST_NAP)
#define PPC_SLEEP stringify_in_c(.long PPC_INST_SLEEP)
Index: linux-ozlabs/arch/powerpc/include/asm/reg.h
===================================================================
--- linux-ozlabs.orig/arch/powerpc/include/asm/reg.h
+++ linux-ozlabs/arch/powerpc/include/asm/reg.h
@@ -496,6 +496,7 @@
#define SPRN_HSRR0 0x13A /* Save/Restore Register 0 */
#define SPRN_HSRR1 0x13B /* Save/Restore Register 1 */
+#define HSRR1_DENORM 0x00100000 /* Denorm exception */
#define SPRN_TBCTL 0x35f /* PA6T Timebase control register */
#define TBCTL_FREEZE 0x0000000000000000ull /* Freeze all tbs */
Index: linux-ozlabs/arch/powerpc/kernel/exceptions-64s.S
===================================================================
--- linux-ozlabs.orig/arch/powerpc/kernel/exceptions-64s.S
+++ linux-ozlabs/arch/powerpc/kernel/exceptions-64s.S
@@ -264,6 +264,31 @@ vsx_unavailable_pSeries_1:
STD_EXCEPTION_HV(0x1200, 0x1202, cbe_system_error)
#endif /* CONFIG_CBE_RAS */
STD_EXCEPTION_PSERIES(0x1300, 0x1300, instruction_breakpoint)
+
+#ifdef CONFIG_PPC_DENORMALISATION
+ . = 0x1500
+ .global denorm_Hypervisor
+denorm_Hypervisor:
+ HMT_MEDIUM
+ mtspr SPRN_SPRG_HSCRATCH0,r13
+ mfspr r13,SPRN_SPRG_HPACA
+ std r9,PACA_EXGEN+EX_R9(r13)
+ std r10,PACA_EXGEN+EX_R10(r13)
+ std r11,PACA_EXGEN+EX_R11(r13)
+ std r12,PACA_EXGEN+EX_R12(r13)
+ mfspr r9,SPRN_SPRG_HSCRATCH0
+ std r9,PACA_EXGEN+EX_R13(r13)
+ mfcr r9
+
+ mfspr r10,SPRN_HSRR1
+ mfspr r11,SPRN_HSRR0 /* save HSRR0 */
+ andis. r10,r10,(HSRR1_DENORM)@h /* denorm? */
+ addi r11,r11,-4 /* HSRR0 is next instruction */
+ bne+ denorm_assist
+
+ EXCEPTION_PROLOG_PSERIES_1(denorm_common, EXC_HV)
+#endif
+
#ifdef CONFIG_CBE_RAS
STD_EXCEPTION_HV(0x1600, 0x1602, cbe_maintenance)
#endif /* CONFIG_CBE_RAS */
@@ -317,6 +342,103 @@ masked_Hinterrupt:
hrfid
b .
+#ifdef CONFIG_PPC_DENORMALISATION
+denorm_assist:
+BEGIN_FTR_SECTION
+/*
+ * To denormalise we need to move a copy of the register to itself.
+ * For POWER6 do that here for all FP regs.
+ */
+ mfmsr r10
+ ori r10,r10,(MSR_FP|MSR_FE0|MSR_FE1)
+ xori r10,r10,(MSR_FE0|MSR_FE1)
+ mtmsrd r10
+ sync
+ fmr 0,0
+ fmr 1,1
+ fmr 2,2
+ fmr 3,3
+ fmr 4,4
+ fmr 5,5
+ fmr 6,6
+ fmr 7,7
+ fmr 8,8
+ fmr 9,9
+ fmr 10,10
+ fmr 11,11
+ fmr 12,12
+ fmr 13,13
+ fmr 14,14
+ fmr 15,15
+ fmr 16,16
+ fmr 17,17
+ fmr 18,18
+ fmr 19,19
+ fmr 20,20
+ fmr 21,21
+ fmr 22,22
+ fmr 23,23
+ fmr 24,24
+ fmr 25,25
+ fmr 26,26
+ fmr 27,27
+ fmr 28,28
+ fmr 29,29
+ fmr 30,30
+ fmr 31,31
+FTR_SECTION_ELSE
+/*
+ * To denormalise we need to move a copy of the register to itself.
+ * For POWER7 do that here for the first 32 VSX registers only.
+ */
+ mfmsr r10
+ oris r10,r10,MSR_VSX@h
+ mtmsrd r10
+ sync
+ XVCPSGNDP(0,0,0)
+ XVCPSGNDP(1,1,1)
+ XVCPSGNDP(2,2,2)
+ XVCPSGNDP(3,3,3)
+ XVCPSGNDP(4,4,4)
+ XVCPSGNDP(5,5,5)
+ XVCPSGNDP(6,6,6)
+ XVCPSGNDP(7,7,7)
+ XVCPSGNDP(8,8,8)
+ XVCPSGNDP(9,9,9)
+ XVCPSGNDP(10,10,10)
+ XVCPSGNDP(11,11,11)
+ XVCPSGNDP(12,12,12)
+ XVCPSGNDP(13,13,13)
+ XVCPSGNDP(14,14,14)
+ XVCPSGNDP(15,15,15)
+ XVCPSGNDP(16,16,16)
+ XVCPSGNDP(17,17,17)
+ XVCPSGNDP(18,18,18)
+ XVCPSGNDP(19,19,19)
+ XVCPSGNDP(20,20,20)
+ XVCPSGNDP(21,21,21)
+ XVCPSGNDP(22,22,22)
+ XVCPSGNDP(23,23,23)
+ XVCPSGNDP(24,24,24)
+ XVCPSGNDP(25,25,25)
+ XVCPSGNDP(26,26,26)
+ XVCPSGNDP(27,27,27)
+ XVCPSGNDP(28,28,28)
+ XVCPSGNDP(29,29,29)
+ XVCPSGNDP(30,30,30)
+ XVCPSGNDP(31,31,31)
+ALT_FTR_SECTION_END_IFCLR(CPU_FTR_HVMODE_206)
+ mtspr SPRN_HSRR0,r11
+ mtcrf 0x80,r9
+ ld r9,PACA_EXGEN+EX_R9(r13)
+ ld r10,PACA_EXGEN+EX_R10(r13)
+ ld r11,PACA_EXGEN+EX_R11(r13)
+ ld r12,PACA_EXGEN+EX_R12(r13)
+ ld r13,PACA_EXGEN+EX_R13(r13)
+ HRFID
+ b .
+#endif
+
.align 7
do_stab_bolted_pSeries:
std r11,PACA_EXSLB+EX_R11(r13)
@@ -419,6 +541,9 @@ machine_check_common:
STD_EXCEPTION_COMMON(0xe60, hmi_exception, .unknown_exception)
STD_EXCEPTION_COMMON_IDLE(0xf00, performance_monitor,
.performance_monitor_exception)
STD_EXCEPTION_COMMON(0x1300, instruction_breakpoint,
.instruction_breakpoint_exception)
+#ifdef CONFIG_PPC_DENORMALISATION
+ STD_EXCEPTION_COMMON(0x1502, denorm, .unknown_exception)
+#endif
#ifdef CONFIG_ALTIVEC
STD_EXCEPTION_COMMON(0x1700, altivec_assist, .altivec_assist_exception)
#else
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