The patch below does not apply to the 4.9-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From faf37c44a105f3608115785f17cbbf3500f8bc71 Mon Sep 17 00:00:00 2001

From: Michael Neuling mikey@neuling.org Date: Fri, 18 May 2018 11:37:42 +1000 Subject: [PATCH] powerpc/64s: Clear PCR on boot

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 Signed-off-by: Michael Ellerman mpe@ellerman.id.au

diff --git a/arch/powerpc/kernel/cpu_setup_power.S b/arch/powerpc/kernel/cpu_setup_power.S index 3f30c994e931..458b928dbd84 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 8ab51f6ca03a..c904477abaf3 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);