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powerpc/64s: Clear PCR on boot

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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>
This commit is contained in:
Michael Neuling 2018-05-18 11:37:42 +10:00 committed by Greg Kroah-Hartman
parent 55a0e02e85
commit 783771fdbf
1 changed files with 4 additions and 0 deletions
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4
arch/powerpc/kernel/cpu_setup_power.S
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@ -27,6 +27,7 @@ _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
@ -40,6 +41,7 @@ _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
@ -55,6 +57,7 @@ _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
@ -74,6 +77,7 @@ _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