[PATCH] powernv: Load correct TOC pointer while waking up from winkle.

Mahesh J Salgaonkar mahesh at linux.vnet.ibm.com
Fri Aug 5 23:43:12 AEST 2016

From: Mahesh Salgaonkar <mahesh at linux.vnet.ibm.com>

The function pnv_restore_hyp_resource() loads the TOC into r2 from
the invalid PACA pointer before fixing r13 value. This do not affect
POWER ISA 3.0 but it does have an impact on POWER ISA 2.07 or less
leading CPU to get stuck forever.

	login: [  471.830433] Processor 120 is stuck.

This can be easily reproducible using following steps:
- Turn off SMT
	$ ppc64_cpu --smt=off
- offline/online any online cpu (Thread 0 of any core which is online)
	$ echo 0 > /sys/devices/system/cpu/cpu<num>/online
	$ echo 1 > /sys/devices/system/cpu/cpu<num>/online

For POWER ISA 2.07 or less, the last bit of HSPRG0 is set indicating
that thread is waking up from winkle. Hence, the last bit of HSPRG0(r13)
needs to be clear before accessing it as PACA to avoid loading invalid
values from invalid PACA pointer.

Fix this by loading TOC after r13 register is corrected.

Signed-off-by: Mahesh Salgaonkar <mahesh at linux.vnet.ibm.com>
 arch/powerpc/kernel/idle_book3s.S |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/idle_book3s.S b/arch/powerpc/kernel/idle_book3s.S
index 8a56a51..45784ec 100644
--- a/arch/powerpc/kernel/idle_book3s.S
+++ b/arch/powerpc/kernel/idle_book3s.S
@@ -363,8 +363,8 @@ _GLOBAL(power9_idle_stop)
  * cr3 - set to gt if waking up with partial/complete hypervisor state loss
-	ld	r2,PACATOC(r13);
+	ld	r2,PACATOC(r13);
 	 * POWER ISA 3. Use PSSCR to determine if we
 	 * are waking up from deep idle state
@@ -395,6 +395,9 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_300)
 	clrldi	r5,r13,63
 	clrrdi	r13,r13,1
+	/* Now that we are sure r13 is corrected, load TOC */
+	ld	r2,PACATOC(r13);
 	cmpwi	cr4,r5,1
 	mtspr	SPRN_HSPRG0,r13

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