* Re: [PATCH] powerpc/64s: Clear PCR on boot
@ 2018-05-25 13:33 Guenter Roeck
2018-05-27 2:22 ` Michael Ellerman
0 siblings, 1 reply; 4+ messages in thread
From: Guenter Roeck @ 2018-05-25 13:33 UTC (permalink / raw)
To: Michael Neuling, Benjamin Herrenschmidt, Paul Mackerras,
Michael Ellerman
Cc: linuxppc-dev, linux-kernel
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 <mikey@neuling.org>
> Cc: stable@vger.kernel.org
> Signed-off-by: Michael Ellerman <mpe@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
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] powerpc/64s: Clear PCR on boot
2018-05-25 13:33 [PATCH] powerpc/64s: Clear PCR on boot Guenter Roeck
@ 2018-05-27 2:22 ` Michael Ellerman
2018-05-27 3:45 ` Guenter Roeck
0 siblings, 1 reply; 4+ messages in thread
From: Michael Ellerman @ 2018-05-27 2:22 UTC (permalink / raw)
To: Guenter Roeck, Michael Neuling, Benjamin Herrenschmidt,
Paul Mackerras, Michael Ellerman
Cc: linuxppc-dev, linux-kernel
On 25 May 2018 11:33:08 pm AEST, Guenter Roeck <linux@roeck-us=2Enet> wrot=
e:
>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=2E
>>=20
>> We've seen this cause problems when a crash (and kdump) occurs while
>> running compat mode guests=2E The kdump kernel then runs with the PCR
>> set and causes problems=2E 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)=2E
>>=20
>
>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=2E
>
>Can you confirm that this is a bug in qemu ?
Hi Guenter,
Thanks for the report=2E As far as I'm concerned this is a qemu bug, that =
register should exist on a bare metal Power8=2E
Will try and get you a qemu patch to fix it=2E
cheers
--=20
Sent from my Android phone with K-9 Mail=2E Please excuse my brevity=2E
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] powerpc/64s: Clear PCR on boot
2018-05-27 2:22 ` Michael Ellerman
@ 2018-05-27 3:45 ` Guenter Roeck
2018-05-28 13:28 ` Benjamin Herrenschmidt
0 siblings, 1 reply; 4+ messages in thread
From: Guenter Roeck @ 2018-05-27 3:45 UTC (permalink / raw)
To: Michael Ellerman
Cc: Michael Neuling, Benjamin Herrenschmidt, Paul Mackerras,
Michael Ellerman, linuxppc-dev, linux-kernel
Hi Michael,
On Sun, May 27, 2018 at 12:22:23PM +1000, Michael Ellerman wrote:
>
>
> On 25 May 2018 11:33:08 pm AEST, Guenter Roeck <linux@roeck-us.net> wrote:
> >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 ?
>
> Hi Guenter,
>
> Thanks for the report. As far as I'm concerned this is a qemu bug, that register should exist on a bare metal Power8.
>
> Will try and get you a qemu patch to fix it.
>
I already have a patch, or at least one that does the trick for me.
Getting qemu patched was not the problem. I just want to be sure that
the problem is indeed a qemu problem.
Thanks,
Guenter
---
>From 1617bac264b4c49d817b6947611affa9b73318f6 Mon Sep 17 00:00:00 2001
From: Guenter Roeck <linux@roeck-us.net>
Date: Fri, 25 May 2018 06:38:40 -0700
Subject: [PATCH] PowerPC: Permit privileged access to SPR_PCR for POWER7+
Without this access, Linux mainline bails out.
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
target/ppc/translate_init.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/target/ppc/translate_init.c b/target/ppc/translate_init.c
index 391b94b..3b09c49 100644
--- a/target/ppc/translate_init.c
+++ b/target/ppc/translate_init.c
@@ -7953,11 +7953,12 @@ static void gen_spr_power6_common(CPUPPCState *env)
#endif
/*
* Register PCR to report POWERPC_EXCP_PRIV_REG instead of
- * POWERPC_EXCP_INVAL_SPR.
+ * POWERPC_EXCP_INVAL_SPR in userspace. Permit privileged
+ * access.
*/
spr_register(env, SPR_PCR, "PCR",
SPR_NOACCESS, SPR_NOACCESS,
- SPR_NOACCESS, SPR_NOACCESS,
+ &spr_read_generic, &spr_write_generic,
0x00000000);
}
--
2.7.4
^ permalink raw reply related [flat|nested] 4+ messages in thread* Re: [PATCH] powerpc/64s: Clear PCR on boot
2018-05-27 3:45 ` Guenter Roeck
@ 2018-05-28 13:28 ` Benjamin Herrenschmidt
0 siblings, 0 replies; 4+ messages in thread
From: Benjamin Herrenschmidt @ 2018-05-28 13:28 UTC (permalink / raw)
To: Guenter Roeck, Michael Ellerman
Cc: Michael Neuling, Paul Mackerras, Michael Ellerman, linuxppc-dev,
linux-kernel
On Sat, 2018-05-26 at 20:45 -0700, Guenter Roeck wrote:
>
> I already have a patch, or at least one that does the trick for me.
> Getting qemu patched was not the problem. I just want to be sure that
> the problem is indeed a qemu problem.
Hey Guenter !
It's not quite the right patch though. The PCR is a hypervisor
priviledged register, your patch makes it supervisor accessible.
I don't have all my stuff at hand to provide a "proper" or tested patch
but it should look like
spr_register_hv(env, SPR_PCR, "PCR",
SPR_NOACCESS, SPR_NOACCESS,
SPR_NOACCESS, SPR_NOACCESS,
&spr_read_generic, &spr_write_generic, 0);
Additionally the TCG ppc instruction decoder should be made to check
the PCR for varous instructions (that or use a specific write callback
that affects the CPU flags) but that's less urgent.
Cheers,
Ben.
> Thanks,
> Guenter
>
> ---
> > From 1617bac264b4c49d817b6947611affa9b73318f6 Mon Sep 17 00:00:00 2001
>
> From: Guenter Roeck <linux@roeck-us.net>
> Date: Fri, 25 May 2018 06:38:40 -0700
> Subject: [PATCH] PowerPC: Permit privileged access to SPR_PCR for POWER7+
>
> Without this access, Linux mainline bails out.
>
> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
> ---
> target/ppc/translate_init.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/target/ppc/translate_init.c b/target/ppc/translate_init.c
> index 391b94b..3b09c49 100644
> --- a/target/ppc/translate_init.c
> +++ b/target/ppc/translate_init.c
> @@ -7953,11 +7953,12 @@ static void gen_spr_power6_common(CPUPPCState *env)
> #endif
> /*
> * Register PCR to report POWERPC_EXCP_PRIV_REG instead of
> - * POWERPC_EXCP_INVAL_SPR.
> + * POWERPC_EXCP_INVAL_SPR in userspace. Permit privileged
> + * access.
> */
> spr_register(env, SPR_PCR, "PCR",
> SPR_NOACCESS, SPR_NOACCESS,
> - SPR_NOACCESS, SPR_NOACCESS,
> + &spr_read_generic, &spr_write_generic,
> 0x00000000);
> }
>
^ permalink raw reply [flat|nested] 4+ messages in thread
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2018-05-28 13:28 ` Benjamin Herrenschmidt
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