Subject: [PATCH] powerpc: Disable HFSCR:TM if TM not supported

From: Benjamin Herrenschmidt <[email-masked]>
Date: Mon, 16 Jan 2017 17:02:24 -0600

Otherwise KVM guests might mess with it even when told not
to causing bad thing interrupts in the host

Signed-off-by: Benjamin Herrenschmidt <[email-masked]>
---
 arch/powerpc/kernel/setup_64.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c
index 6824157..31d7071 100644
--- a/arch/powerpc/kernel/setup_64.c
+++ b/arch/powerpc/kernel/setup_64.c
@@ -245,6 +245,16 @@ static void cpu_ready_for_interrupts(void)
 		mtspr(SPRN_LPCR, lpcr | LPCR_AIL_3);
 	}
 
+	/*
+	 * Fixup HFSCR:TM based on CPU features. The bit is set by our
+	 * early asm init because at that point we haven't updated our
+	 * CPU features from firmware and device-tree. Here we have,
+	 * so let's do it
+	 */
+	if (early_cpu_has_feature(CPU_FTR_HVMODE) &&
+	    !early_cpu_has_feature(CPU_FTR_TM_COMP))
+		mtspr(SPRN_HFSCR, mfspr(SPRN_HFSCR) & ~HFSCR_TM);
+
 	/* Set IR and DR in PACA MSR */
 	get_paca()->kernel_msr = MSR_KERNEL;
 }