Subject: [PATCH v5 6/7] powerpc/powernv: Access LDBAR only if ultravisor disabled

From: Claudio Carvalho <[email-masked]>
Date: Thu, 8 Aug 2019 01:05:54 -0300

LDBAR is a per-thread SPR populated and used by the thread-imc pmu
driver to dump the data counter into memory. It contains memory along
with few other configuration bits. LDBAR is populated and enabled only
when any of the thread imc pmu events are monitored.

In ultravisor enabled systems, LDBAR becomes ultravisor privileged and
an attempt to write to it will cause a Hypervisor Emulation Assistance
interrupt.

In ultravisor enabled systems, the ultravisor is responsible to maintain
the LDBAR (e.g. save and restore it).

This restricts LDBAR access to only when ultravisor is disabled.

Signed-off-by: Claudio Carvalho <[email-masked]>
Reviewed-by: Ram Pai <[email-masked]>
Reviewed-by: Ryan Grimm <[email-masked]>
---
 arch/powerpc/platforms/powernv/idle.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/platforms/powernv/idle.c b/arch/powerpc/platforms/powernv/idle.c
index 210fb73a5121..14018463a8f0 100644
--- a/arch/powerpc/platforms/powernv/idle.c
+++ b/arch/powerpc/platforms/powernv/idle.c
@@ -679,7 +679,8 @@ static unsigned long power9_idle_stop(unsigned long psscr, bool mmu_on)
 		sprs.ptcr	= mfspr(SPRN_PTCR);
 		sprs.rpr	= mfspr(SPRN_RPR);
 		sprs.tscr	= mfspr(SPRN_TSCR);
-		sprs.ldbar	= mfspr(SPRN_LDBAR);
+		if (!firmware_has_feature(FW_FEATURE_ULTRAVISOR))
+			sprs.ldbar = mfspr(SPRN_LDBAR);
 
 		sprs_saved = true;
 
@@ -793,7 +794,8 @@ static unsigned long power9_idle_stop(unsigned long psscr, bool mmu_on)
 	mtspr(SPRN_MMCR0,	sprs.mmcr0);
 	mtspr(SPRN_MMCR1,	sprs.mmcr1);
 	mtspr(SPRN_MMCR2,	sprs.mmcr2);
-	mtspr(SPRN_LDBAR,	sprs.ldbar);
+	if (!firmware_has_feature(FW_FEATURE_ULTRAVISOR))
+		mtspr(SPRN_LDBAR, sprs.ldbar);
 
 	mtspr(SPRN_SPRG3,	local_paca->sprg_vdso);
 
-- 
2.20.1