powerpc: Add denormalisation exception handling for POWER6/7

On POWER6 and POWER7 if the input operand to an instruction is a
denormalised single precision binary floating point value 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 <mikey@neuling.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 98e513b..748ccaa 100644 (file)
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -560,6 +560,14 @@ 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"
+       depends on PPC_BOOK3S_64
+       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"
 

diff --git a/arch/powerpc/configs/ppc64_defconfig b/arch/powerpc/configs/ppc64_defconfig
index db27c82..e263e6a 100644 (file)
--- a/arch/powerpc/configs/ppc64_defconfig
+++ b/arch/powerpc/configs/ppc64_defconfig
@@ -51,6 +51,7 @@ 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

diff --git a/arch/powerpc/configs/pseries_defconfig b/arch/powerpc/configs/pseries_defconfig
index 1f65b3c..c169dfb 100644 (file)
--- a/arch/powerpc/configs/pseries_defconfig
+++ b/arch/powerpc/configs/pseries_defconfig
@@ -48,6 +48,7 @@ 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

diff --git a/arch/powerpc/include/asm/ppc-opcode.h b/arch/powerpc/include/asm/ppc-opcode.h
index 4c25319..5f73ce6 100644 (file)
--- a/arch/powerpc/include/asm/ppc-opcode.h
+++ b/arch/powerpc/include/asm/ppc-opcode.h
@@ -126,6 +126,7 @@
 #define PPC_INST_TLBIVAX               0x7c000624
 #define PPC_INST_TLBSRX_DOT            0x7c0006a5
 #define PPC_INST_XXLOR                 0xf0000510
+#define PPC_INST_XVCPSGNDP             0xf0000780
 
 #define PPC_INST_NAP                   0x4c000364
 #define PPC_INST_SLEEP                 0x4c0003a4
@@ -277,6 +278,8 @@
                                               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 (PPC_INST_XVCPSGNDP | \
+                                              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)

diff --git a/arch/powerpc/include/asm/reg.h b/arch/powerpc/include/asm/reg.h
index 121a90b..a1096fb 100644 (file)
--- a/arch/powerpc/include/asm/reg.h
+++ b/arch/powerpc/include/asm/reg.h
@@ -524,6 +524,7 @@
 
 #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 */

diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index 39aa97d..5eb0056 100644 (file)
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -275,6 +275,31 @@ vsx_unavailable_pSeries_1:
        STD_EXCEPTION_PSERIES(0x1300, 0x1300, instruction_breakpoint)
        KVM_HANDLER_PR_SKIP(PACA_EXGEN, EXC_STD, 0x1300)
 
+       . = 0x1500
+       .global denorm_Hypervisor
+denorm_exception_hv:
+       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
+
+#ifdef CONFIG_PPC_DENORMALISATION
+       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
+#endif
+
+       EXCEPTION_PROLOG_PSERIES_1(denorm_common, EXC_HV)
+       KVM_HANDLER_SKIP(PACA_EXGEN, EXC_STD, 0x1500)
+
 #ifdef CONFIG_CBE_RAS
        STD_EXCEPTION_HV(0x1600, 0x1602, cbe_maintenance)
        KVM_HANDLER_SKIP(PACA_EXGEN, EXC_HV, 0x1602)
@@ -336,6 +361,103 @@ do_stab_bolted_pSeries:
        KVM_HANDLER_PR(PACA_EXGEN, EXC_STD, 0x900)
        KVM_HANDLER(PACA_EXGEN, EXC_HV, 0x982)
 
+#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_ARCH_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
        /* moved from 0xe00 */
        STD_EXCEPTION_HV(., 0xe02, h_data_storage)
@@ -495,6 +617,7 @@ machine_check_common:
         STD_EXCEPTION_COMMON(0xe60, hmi_exception, .unknown_exception)
        STD_EXCEPTION_COMMON_ASYNC(0xf00, performance_monitor, .performance_monitor_exception)
        STD_EXCEPTION_COMMON(0x1300, instruction_breakpoint, .instruction_breakpoint_exception)
+       STD_EXCEPTION_COMMON(0x1502, denorm, .unknown_exception)
 #ifdef CONFIG_ALTIVEC
        STD_EXCEPTION_COMMON(0x1700, altivec_assist, .altivec_assist_exception)
 #else