[PATCH] powepc: Clear PCR on boot

[Michael Neuling]

Clear the PCR on boot to ensure we are not running in a compat mode.

We've seen this cause problems when a crash (and kdump) occurs while
running compat mode guests. The kdump kernel then runs with the PCR
set and causes problems. The symptom in the kdump kernel (also seen in
petitboot after fast-reboot) is early userspace programs taking
sigills on newer instructions (seen in libc).

Signed-off-by: Michael Neuling <mi...@neuling.org>
Cc: <sta...@vger.kernel.org>
---
 arch/powerpc/kernel/cpu_setup_power.S | 6 ++++++
 arch/powerpc/kernel/dt_cpu_ftrs.c     | 1 +
 2 files changed, 7 insertions(+)

diff --git a/arch/powerpc/kernel/cpu_setup_power.S 
b/arch/powerpc/kernel/cpu_setup_power.S
index 3f30c994e9..458b928dbd 100644
--- a/arch/powerpc/kernel/cpu_setup_power.S
+++ b/arch/powerpc/kernel/cpu_setup_power.S
@@ -28,6 +28,7 @@ _GLOBAL(__setup_cpu_power7)
        beqlr
        li      r0,0
        mtspr   SPRN_LPID,r0
+       mtspr   SPRN_PCR,r0
        mfspr   r3,SPRN_LPCR
        li      r4,(LPCR_LPES1 >> LPCR_LPES_SH)
        bl      __init_LPCR_ISA206
@@ -41,6 +42,7 @@ _GLOBAL(__restore_cpu_power7)
        beqlr
        li      r0,0
        mtspr   SPRN_LPID,r0
+       mtspr   SPRN_PCR,r0
        mfspr   r3,SPRN_LPCR
        li      r4,(LPCR_LPES1 >> LPCR_LPES_SH)
        bl      __init_LPCR_ISA206
@@ -57,6 +59,7 @@ _GLOBAL(__setup_cpu_power8)
        beqlr
        li      r0,0
        mtspr   SPRN_LPID,r0
+       mtspr   SPRN_PCR,r0
        mfspr   r3,SPRN_LPCR
        ori     r3, r3, LPCR_PECEDH
        li      r4,0 /* LPES = 0 */
@@ -78,6 +81,7 @@ _GLOBAL(__restore_cpu_power8)
        beqlr
        li      r0,0
        mtspr   SPRN_LPID,r0
+       mtspr   SPRN_PCR,r0
        mfspr   r3,SPRN_LPCR
        ori     r3, r3, LPCR_PECEDH
        li      r4,0 /* LPES = 0 */
@@ -99,6 +103,7 @@ _GLOBAL(__setup_cpu_power9)
        mtspr   SPRN_PSSCR,r0
        mtspr   SPRN_LPID,r0
        mtspr   SPRN_PID,r0
+       mtspr   SPRN_PCR,r0
        mfspr   r3,SPRN_LPCR
        LOAD_REG_IMMEDIATE(r4, LPCR_PECEDH | LPCR_PECE_HVEE | LPCR_HVICE  | 
LPCR_HEIC)
        or      r3, r3, r4
@@ -123,6 +128,7 @@ _GLOBAL(__restore_cpu_power9)
        mtspr   SPRN_PSSCR,r0
        mtspr   SPRN_LPID,r0
        mtspr   SPRN_PID,r0
+       mtspr   SPRN_PCR,r0
        mfspr   r3,SPRN_LPCR
        LOAD_REG_IMMEDIATE(r4, LPCR_PECEDH | LPCR_PECE_HVEE | LPCR_HVICE | 
LPCR_HEIC)
        or      r3, r3, r4
diff --git a/arch/powerpc/kernel/dt_cpu_ftrs.c 
b/arch/powerpc/kernel/dt_cpu_ftrs.c
index 8ab51f6ca0..c904477aba 100644
--- a/arch/powerpc/kernel/dt_cpu_ftrs.c
+++ b/arch/powerpc/kernel/dt_cpu_ftrs.c
@@ -101,6 +101,7 @@ static void __restore_cpu_cpufeatures(void)
        if (hv_mode) {
                mtspr(SPRN_LPID, 0);
                mtspr(SPRN_HFSCR, system_registers.hfscr);
+               mtspr(SPRN_PCR, 0);
        }
        mtspr(SPRN_FSCR, system_registers.fscr);
 
-- 
2.14.1