powerpc/64s: Clear PCR on boot

commit faf37c44a105f3608115785f17cbbf3500f8bc71 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/powerpc/kernel/cpu_setup_power.S b/arch/powerpc/kernel/cpu_setup_power.S
index 679bbe714e8561b8c259f37bbfc9db8264555554..9daede99c1316182205fbe0c13ad20af33c1c388 100644 (file)
--- 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
@@ -42,6 +43,7 @@ _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
@@ -59,6 +61,7 @@ _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 */
@@ -81,6 +84,7 @@ _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 */
@@ -103,6 +107,7 @@ _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
@@ -128,6 +133,7 @@ _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 f047ae1b62712ca1b2dca4d704c7d6b366c08bfc..2dba206b065aa0c673822c39efd6ef9428c9907b 100644 (file)
--- a/arch/powerpc/kernel/dt_cpu_ftrs.c
+++ b/arch/powerpc/kernel/dt_cpu_ftrs.c
@@ -137,6 +137,7 @@ 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);