On Fri, May 18, 2018 at 11:37:42AM +1000, Michael Neuling wrote:
> 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).
>
Hi folks,
this patch causes qemu to bail out with
Trying to write privileged spr 338 (0x152) at c000000000033454
when running it with "-M powernv -cpu POWER8" and powernv_defconfig.
Can you confirm that this is a bug in qemu ?
Thanks,
Guenter
> Signed-off-by: Michael Neuling <mi...@neuling.org>
> Cc: sta...@vger.kernel.org
> Signed-off-by: Michael Ellerman <m...@ellerman.id.au>
> ---
> 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 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);
>
> --
> 2.7.4
