[PATCH v5 5/7] powerpc/mm: Write to PTCR only if ultravisor disabled

[Claudio Carvalho <cclaudio@xxxxxxxxxxxxx>]

In ultravisor enabled systems, PTCR becomes ultravisor privileged only
for writing and an attempt to write to it will cause a Hypervisor
Emulation Assitance interrupt.

This patch adds the try_set_ptcr(val) macro as an accessor to
mtspr(SPRN_PTCR, val), which will be executed only if ultravisor
disabled.

Signed-off-by: Claudio Carvalho <cclaudio@xxxxxxxxxxxxx>
---
 arch/powerpc/include/asm/reg.h           | 13 +++++++++++++
 arch/powerpc/mm/book3s64/hash_utils.c    |  4 ++--
 arch/powerpc/mm/book3s64/pgtable.c       |  2 +-
 arch/powerpc/mm/book3s64/radix_pgtable.c |  6 +++---
 4 files changed, 19 insertions(+), 6 deletions(-)

diff --git a/arch/powerpc/include/asm/reg.h b/arch/powerpc/include/asm/reg.h
index 10caa145f98b..14139b1ebdb8 100644
--- a/arch/powerpc/include/asm/reg.h
+++ b/arch/powerpc/include/asm/reg.h
@@ -15,6 +15,7 @@
 #include <asm/cputable.h>
 #include <asm/asm-const.h>
 #include <asm/feature-fixups.h>
+#include <asm/firmware.h>
 
 /* Pickup Book E specific registers. */
 #if defined(CONFIG_BOOKE) || defined(CONFIG_40x)
@@ -1452,6 +1453,18 @@ static inline void update_power8_hid0(unsigned long hid0)
 	 */
 	asm volatile("sync; mtspr %0,%1; isync":: "i"(SPRN_HID0), "r"(hid0));
 }
+
+/*
+ * In ultravisor enabled systems, PTCR becomes ultravisor privileged only for
+ * writing and an attempt to write to it will cause a Hypervisor Emulation
+ * Assistance interrupt.
+ */
+#define try_set_ptcr(val)						\
+	do {								\
+		if (!firmware_has_feature(FW_FEATURE_ULTRAVISOR))	\
+			mtspr(SPRN_PTCR, val);				\
+	} while (0)
+
 #endif /* __ASSEMBLY__ */
 #endif /* __KERNEL__ */
 #endif /* _ASM_POWERPC_REG_H */
diff --git a/arch/powerpc/mm/book3s64/hash_utils.c b/arch/powerpc/mm/book3s64/hash_utils.c
index 25a2cf32d544..048b7f58deae 100644
--- a/arch/powerpc/mm/book3s64/hash_utils.c
+++ b/arch/powerpc/mm/book3s64/hash_utils.c
@@ -1079,8 +1079,8 @@ void hash__early_init_mmu_secondary(void)
 		if (!cpu_has_feature(CPU_FTR_ARCH_300))
 			mtspr(SPRN_SDR1, _SDR1);
 		else
-			mtspr(SPRN_PTCR,
-			      __pa(partition_tb) | (PATB_SIZE_SHIFT - 12));
+			try_set_ptcr(__pa(partition_tb) |
+				     (PATB_SIZE_SHIFT - 12));
 	}
 	/* Initialize SLB */
 	slb_initialize();
diff --git a/arch/powerpc/mm/book3s64/pgtable.c b/arch/powerpc/mm/book3s64/pgtable.c
index 033731f5dbaa..016c6ccb5b81 100644
--- a/arch/powerpc/mm/book3s64/pgtable.c
+++ b/arch/powerpc/mm/book3s64/pgtable.c
@@ -219,7 +219,7 @@ void __init mmu_partition_table_init(void)
 	 * 64 K size.
 	 */
 	ptcr = __pa(partition_tb) | (PATB_SIZE_SHIFT - 12);
-	mtspr(SPRN_PTCR, ptcr);
+	try_set_ptcr(ptcr);
 	powernv_set_nmmu_ptcr(ptcr);
 }
 
diff --git a/arch/powerpc/mm/book3s64/radix_pgtable.c b/arch/powerpc/mm/book3s64/radix_pgtable.c
index e92c6472a20c..246b32550eab 100644
--- a/arch/powerpc/mm/book3s64/radix_pgtable.c
+++ b/arch/powerpc/mm/book3s64/radix_pgtable.c
@@ -654,8 +654,8 @@ void radix__early_init_mmu_secondary(void)
 		lpcr = mfspr(SPRN_LPCR);
 		mtspr(SPRN_LPCR, lpcr | LPCR_UPRT | LPCR_HR);
 
-		mtspr(SPRN_PTCR,
-		      __pa(partition_tb) | (PATB_SIZE_SHIFT - 12));
+		try_set_ptcr(__pa(partition_tb) | (PATB_SIZE_SHIFT - 12));
+
 		radix_init_amor();
 	}
 
@@ -671,7 +671,7 @@ void radix__mmu_cleanup_all(void)
 	if (!firmware_has_feature(FW_FEATURE_LPAR)) {
 		lpcr = mfspr(SPRN_LPCR);
 		mtspr(SPRN_LPCR, lpcr & ~LPCR_UPRT);
-		mtspr(SPRN_PTCR, 0);
+		try_set_ptcr(0);
 		powernv_set_nmmu_ptcr(0);
 		radix__flush_tlb_all();
 	}
-- 
2.20.1