Clear the PCR (Processor Compatibility Register) on boot to ensure we are not running in a compatibility 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 mikey@neuling.org Cc: stable@vger.kernel.org # v4.9 Signed-off-by: Michael Ellerman mpe@ellerman.id.au --

Greg, This is a backport for v4.9 only since the original patch didn't apply.

Commit faf37c44a105f3608115785f17cbbf3500f8bc71 upstream. --- arch/powerpc/kernel/cpu_setup_power.S | 6 ++++++ 1 file changed, 6 insertions(+)

diff --git a/arch/powerpc/kernel/cpu_setup_power.S b/arch/powerpc/kernel/cpu_setup_power.S index 9e05c8828e..ff45d007d1 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 bl __init_LPCR bl __init_tlb_power7 @@ -41,6 +42,7 @@ _GLOBAL(__restore_cpu_power7) beqlr li r0,0 mtspr SPRN_LPID,r0 + mtspr SPRN_PCR,r0 mfspr r3,SPRN_LPCR bl __init_LPCR bl __init_tlb_power7 @@ -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 bl __init_LPCR @@ -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 bl __init_LPCR @@ -98,6 +102,7 @@ _GLOBAL(__setup_cpu_power9) li r0,0 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) or r3, r3, r4 @@ -121,6 +126,7 @@ _GLOBAL(__restore_cpu_power9) li r0,0 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) or r3, r3, r4