FAILED: patch "[PATCH] KVM: arm64: Fix caching of host MDCR_EL2 value" failed to apply to 4.9-stable tree

The patch below does not apply to the 4.9-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From: Mark Rutland <[email protected]>
Date: Wed, 17 Oct 2018 17:42:10 +0100
Subject: [PATCH] KVM: arm64: Fix caching of host MDCR_EL2 value

At boot time, KVM stashes the host MDCR_EL2 value, but only does this when the kernel is not running in hyp mode (i.e. is non-VHE). In these cases, the stashed value of MDCR_EL2.HPMN happens to be zero, which can lead to CONSTRAINED UNPREDICTABLE behaviour.

Since we use this value to derive the MDCR_EL2 value when switching to/from a guest, after a guest have been run, the performance counters do not behave as expected. This has been observed to result in accesses via PMXEVTYPER_EL0 and PMXEVCNTR_EL0 not affecting the relevant counters, resulting in events not being counted. In these cases, only the fixed-purpose cycle counter appears to work as expected.

Fix this by always stashing the host MDCR_EL2 value, regardless of VHE.

index 4ce99bb223bc..4c5ff06b18f9 100644
@@ -1296,8 +1296,6 @@ static void cpu_init_hyp_mode(void *dummy)
 
 	__cpu_init_hyp_mode(pgd_ptr, hyp_stack_ptr, vector_ptr);
 	__cpu_init_stage2();
-
-	kvm_arm_init_debug();
 }
 
 static void cpu_hyp_reset(void)

@@ -1315,6 +1313,8 @@ static void cpu_hyp_reinit(void)
 	else
 		cpu_init_hyp_mode(NULL);
 
+	kvm_arm_init_debug();
+
 	if (vgic_present)
 		kvm_vgic_init_cpu_hardware();
 }