[RFC PATCH v5 24/38] KVM: arm64: Move accesses to MDCR_EL2 out of __{activate, deactivate}_traps_common

[Alexandru Elisei]

To run a guest with SPE, MDCR_EL2 must be configured such that the buffer
owning regime is EL1&0. With VHE enabled, the guest runs at EL2 and
changing the owning regime to EL1&0 in vcpu_put() would mean creating an
extended blackout window for the host.

Move the acceses to MDCR_EL2 out of __activate_traps_common() and
__deactivate_traps_common() to prepare for executing them later in the run
loop in the VHE case.

No functional change intended.

Signed-off-by: Alexandru Elisei <alexandru.elisei at arm.com>
---
 arch/arm64/kvm/hyp/include/hyp/switch.h | 16 +++++++++++-----
 arch/arm64/kvm/hyp/nvhe/switch.c        |  2 ++
 arch/arm64/kvm/hyp/vhe/switch.c         |  2 ++
 3 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/kvm/hyp/include/hyp/switch.h b/arch/arm64/kvm/hyp/include/hyp/switch.h
index 7a0af1d39303..cf9b66a2acb0 100644
--- a/arch/arm64/kvm/hyp/include/hyp/switch.h
+++ b/arch/arm64/kvm/hyp/include/hyp/switch.h
@@ -97,20 +97,26 @@ static inline void __activate_traps_common(struct kvm_vcpu *vcpu)
 		write_sysreg(0, pmselr_el0);
 		write_sysreg(ARMV8_PMU_USERENR_MASK, pmuserenr_el0);
 	}
-
-	vcpu->arch.mdcr_el2_host = read_sysreg(mdcr_el2);
-	write_sysreg(vcpu->arch.mdcr_el2, mdcr_el2);
 }
 
 static inline void __deactivate_traps_common(struct kvm_vcpu *vcpu)
 {
-	write_sysreg(vcpu->arch.mdcr_el2_host, mdcr_el2);
-
 	write_sysreg(0, hstr_el2);
 	if (kvm_arm_support_pmu_v3())
 		write_sysreg(0, pmuserenr_el0);
 }
 
+static inline void __restore_guest_mdcr_el2(struct kvm_vcpu *vcpu)
+{
+	vcpu->arch.mdcr_el2_host = read_sysreg(mdcr_el2);
+	write_sysreg(vcpu->arch.mdcr_el2, mdcr_el2);
+}
+
+static inline void __restore_host_mdcr_el2(struct kvm_vcpu *vcpu)
+{
+	write_sysreg(vcpu->arch.mdcr_el2_host, mdcr_el2);
+}
+
 static inline void ___activate_traps(struct kvm_vcpu *vcpu)
 {
 	u64 hcr = vcpu->arch.hcr_el2;
diff --git a/arch/arm64/kvm/hyp/nvhe/switch.c b/arch/arm64/kvm/hyp/nvhe/switch.c
index c0e3fed26d93..d1f55514effc 100644
--- a/arch/arm64/kvm/hyp/nvhe/switch.c
+++ b/arch/arm64/kvm/hyp/nvhe/switch.c
@@ -41,6 +41,7 @@ static void __activate_traps(struct kvm_vcpu *vcpu)
 
 	___activate_traps(vcpu);
 	__activate_traps_common(vcpu);
+	__restore_guest_mdcr_el2(vcpu);
 
 	val = vcpu->arch.cptr_el2;
 	val |= CPTR_EL2_TTA | CPTR_EL2_TAM;
@@ -91,6 +92,7 @@ static void __deactivate_traps(struct kvm_vcpu *vcpu)
 		isb();
 	}
 
+	__restore_host_mdcr_el2(vcpu);
 	__deactivate_traps_common(vcpu);
 
 	write_sysreg(this_cpu_ptr(&kvm_init_params)->hcr_el2, hcr_el2);
diff --git a/arch/arm64/kvm/hyp/vhe/switch.c b/arch/arm64/kvm/hyp/vhe/switch.c
index 5a2cb5d9bc4b..f85a13bfad3d 100644
--- a/arch/arm64/kvm/hyp/vhe/switch.c
+++ b/arch/arm64/kvm/hyp/vhe/switch.c
@@ -89,10 +89,12 @@ NOKPROBE_SYMBOL(__deactivate_traps);
 void activate_traps_vhe_load(struct kvm_vcpu *vcpu)
 {
 	__activate_traps_common(vcpu);
+	__restore_guest_mdcr_el2(vcpu);
 }
 
 void deactivate_traps_vhe_put(struct kvm_vcpu *vcpu)
 {
+	__restore_host_mdcr_el2(vcpu);
 	__deactivate_traps_common(vcpu);
 }
 
-- 
2.33.1