powerpc/64s: relocation, register save fixes for system reset interrupt

This patch does a couple of things. First of all, powernv immediately
explodes when running a relocated kernel, because the system reset
exception for handling sleeps does not do correct relocated branches.

Secondly, the sleep handling code trashes the condition and cfar
registers, which we would like to preserve for debugging purposes (for
non-sleep case exception).

This patch changes the exception to use the standard format that saves
registers before any tests or branches are made. It adds the test for
idle-wakeup as an "extra" to break out of the normal exception path.
Then it branches to a relocated idle handler that calls the various
idle handling functions.

After this patch, POWER8 CPU simulator now boots powernv kernel that is
running at non-zero.

Fixes: 948cf67c4726 ("powerpc: Add NAP mode support on Power7 in HV mode")
Cc: stable@vger.kernel.org # v3.0+
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Acked-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
Acked-by: Balbir Singh <bsingharora@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

diff --git a/arch/powerpc/include/asm/exception-64s.h b/arch/powerpc/include/asm/exception-64s.h
index 2e4e7d8..84d49b1 100644 (file)
--- a/arch/powerpc/include/asm/exception-64s.h
+++ b/arch/powerpc/include/asm/exception-64s.h
@@ -93,6 +93,10 @@
        ld      reg,PACAKBASE(r13);     /* get high part of &label */   \
        ori     reg,reg,(FIXED_SYMBOL_ABS_ADDR(label))@l;
 
+#define __LOAD_HANDLER(reg, label)                                     \
+       ld      reg,PACAKBASE(r13);                                     \
+       ori     reg,reg,(ABS_ADDR(label))@l;
+
 /* Exception register prefixes */
 #define EXC_HV H
 #define EXC_STD
@@ -208,6 +212,18 @@ END_FTR_SECTION_NESTED(ftr,ftr,943)
 #define kvmppc_interrupt kvmppc_interrupt_pr
 #endif
 
+#ifdef CONFIG_RELOCATABLE
+#define BRANCH_TO_COMMON(reg, label)                                   \
+       __LOAD_HANDLER(reg, label);                                     \
+       mtctr   reg;                                                    \
+       bctr
+
+#else
+#define BRANCH_TO_COMMON(reg, label)                                   \
+       b       label
+
+#endif
+
 #define __KVM_HANDLER_PROLOG(area, n)                                  \
        BEGIN_FTR_SECTION_NESTED(947)                                   \
        ld      r10,area+EX_CFAR(r13);                                  \

diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index f129408..08ba447 100644 (file)
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -95,19 +95,35 @@ __start_interrupts:
 /* No virt vectors corresponding with 0x0..0x100 */
 EXC_VIRT_NONE(0x4000, 0x4100)
 
-EXC_REAL_BEGIN(system_reset, 0x100, 0x200)
-       SET_SCRATCH0(r13)
+
 #ifdef CONFIG_PPC_P7_NAP
-BEGIN_FTR_SECTION
-       /* Running native on arch 2.06 or later, check if we are
-        * waking up from nap/sleep/winkle.
+       /*
+        * If running native on arch 2.06 or later, check if we are waking up
+        * from nap/sleep/winkle, and branch to idle handler.
         */
-       mfspr   r13,SPRN_SRR1
-       rlwinm. r13,r13,47-31,30,31
-       beq     9f
+#define IDLETEST(n)                                                    \
+       BEGIN_FTR_SECTION ;                                             \
+       mfspr   r10,SPRN_SRR1 ;                                         \
+       rlwinm. r10,r10,47-31,30,31 ;                                   \
+       beq-    1f ;                                                    \
+       cmpwi   cr3,r10,2 ;                                             \
+       BRANCH_TO_COMMON(r10, system_reset_idle_common) ;               \
+1:                                                                     \
+       END_FTR_SECTION_IFSET(CPU_FTR_HVMODE | CPU_FTR_ARCH_206)
+#else
+#define IDLETEST NOTEST
+#endif
 
-       cmpwi   cr3,r13,2
-       GET_PACA(r13)
+EXC_REAL_BEGIN(system_reset, 0x100, 0x200)
+       SET_SCRATCH0(r13)
+       EXCEPTION_PROLOG_PSERIES(PACA_EXGEN, system_reset_common, EXC_STD,
+                                IDLETEST, 0x100)
+
+EXC_REAL_END(system_reset, 0x100, 0x200)
+EXC_VIRT_NONE(0x4100, 0x4200)
+
+#ifdef CONFIG_PPC_P7_NAP
+EXC_COMMON_BEGIN(system_reset_idle_common)
        bl      pnv_restore_hyp_resource
 
        li      r0,PNV_THREAD_RUNNING
@@ -130,14 +146,8 @@ BEGIN_FTR_SECTION
        blt     cr3,2f
        b       pnv_wakeup_loss
 2:     b       pnv_wakeup_noloss
+#endif
 
-9:
-END_FTR_SECTION_IFSET(CPU_FTR_HVMODE | CPU_FTR_ARCH_206)
-#endif /* CONFIG_PPC_P7_NAP */
-       EXCEPTION_PROLOG_PSERIES(PACA_EXGEN, system_reset_common, EXC_STD,
-                                NOTEST, 0x100)
-EXC_REAL_END(system_reset, 0x100, 0x200)
-EXC_VIRT_NONE(0x4100, 0x4200)
 EXC_COMMON(system_reset_common, 0x100, system_reset_exception)
 
 #ifdef CONFIG_PPC_PSERIES
@@ -817,10 +827,8 @@ EXC_VIRT(trap_0b, 0x4b00, 0x4c00, 0xb00)
 TRAMP_KVM(PACA_EXGEN, 0xb00)
 EXC_COMMON(trap_0b_common, 0xb00, unknown_exception)
 
-
-#define LOAD_SYSCALL_HANDLER(reg)                              \
-       ld      reg,PACAKBASE(r13);                             \
-       ori     reg,reg,(ABS_ADDR(system_call_common))@l;
+#define LOAD_SYSCALL_HANDLER(reg)                                      \
+       __LOAD_HANDLER(reg, system_call_common)
 
 /* Syscall routine is used twice, in reloc-off and reloc-on paths */
 #define SYSCALL_PSERIES_1                                      \