[PATCH 10/28] KVM: arm64: Relax CNTHCTL_EL2 handling when FEAT_NV2p1 is present

[Marc Zyngier]

With NV2p1, it is no longer necessary to use the split approach
where bits of CNTHCTL_EL2 cannot be accessed via CNTKCTL_EL1,
and we can treat the CNTKCTL_EL1 accessor as if it was "normal".

Key the special casing on FEAT_NV2P1 not being implemented.

Signed-off-by: Marc Zyngier <maz at kernel.org>
---
 arch/arm64/kvm/arch_timer.c        | 10 ++++++++--
 arch/arm64/kvm/hyp/vhe/sysreg-sr.c | 13 ++++++++++---
 arch/arm64/kvm/sys_regs.c          |  6 ++++--
 3 files changed, 22 insertions(+), 7 deletions(-)

diff --git a/arch/arm64/kvm/arch_timer.c b/arch/arm64/kvm/arch_timer.c
index 4155fe89b58a1..db60facad9f3c 100644
--- a/arch/arm64/kvm/arch_timer.c
+++ b/arch/arm64/kvm/arch_timer.c
@@ -876,8 +876,14 @@ static void timer_set_traps(struct kvm_vcpu *vcpu, struct timer_map *map)
 	assign_clear_set_bit(tvt02, CNTHCTL_EL1NVVCT, clr, set);
 	assign_clear_set_bit(tpt02, CNTHCTL_EL1NVPCT, clr, set);
 
-	/* This only happens on VHE, so use the CNTHCTL_EL2 accessor. */
-	sysreg_clear_set(cnthctl_el2, clr, set);
+	/*
+	 * This only happens on VHE, so use the CNTHCTL_EL2 accessor, unless
+	 * we are sure CNTKCTL_EL1 is completely stateful with FEAT_NV2p1.
+	 */
+	if (!cpus_have_final_cap(ARM64_HAS_NV2P1))
+		sysreg_clear_set(cnthctl_el2, clr, set);
+	else
+		sysreg_clear_set(cntkctl_el1, clr, set);
 }
 
 void kvm_timer_vcpu_load(struct kvm_vcpu *vcpu)
diff --git a/arch/arm64/kvm/hyp/vhe/sysreg-sr.c b/arch/arm64/kvm/hyp/vhe/sysreg-sr.c
index 6f0f046e4ca4e..0c4ef1ce32ae7 100644
--- a/arch/arm64/kvm/hyp/vhe/sysreg-sr.c
+++ b/arch/arm64/kvm/hyp/vhe/sysreg-sr.c
@@ -69,11 +69,18 @@ static void __sysreg_save_vel2_state(struct kvm_vcpu *vcpu)
 		 * The EL1 view of CNTKCTL_EL1 has a bunch of RES0 bits where
 		 * the interesting CNTHCTL_EL2 bits live. So preserve these
 		 * bits when reading back the guest-visible value.
+		 *
+		 * While NV2p1 fixes some of that, it makes CNTHCTL_EL2.ECV
+		 * even more broken than it already was with NV2.
 		 */
 		val = read_sysreg_el1(SYS_CNTKCTL);
-		val &= CNTKCTL_VALID_BITS;
-		__vcpu_rmw_sys_reg(vcpu, CNTHCTL_EL2, &=, ~CNTKCTL_VALID_BITS);
-		__vcpu_rmw_sys_reg(vcpu, CNTHCTL_EL2, |=, val);
+		if (!cpus_have_final_cap(ARM64_HAS_NV2P1)) {
+			val &= CNTKCTL_VALID_BITS;
+			__vcpu_rmw_sys_reg(vcpu, CNTHCTL_EL2, &=, ~CNTKCTL_VALID_BITS);
+			__vcpu_rmw_sys_reg(vcpu, CNTHCTL_EL2, |=, val);
+		} else {
+			__vcpu_assign_sys_reg(vcpu, CNTHCTL_EL2, val);
+		}
 	}
 
 	__vcpu_assign_sys_reg(vcpu, SP_EL2,	 read_sysreg(sp_el1));
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 1dfc1f88bec82..9439c5b2b1fe8 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -322,8 +322,10 @@ u64 vcpu_read_sys_reg(const struct kvm_vcpu *vcpu, enum vcpu_sysreg reg)
 		switch (reg) {
 		case CNTHCTL_EL2:
 			val = read_sysreg_el1(SYS_CNTKCTL);
-			val &= CNTKCTL_VALID_BITS;
-			val |= __vcpu_sys_reg(vcpu, reg) & ~CNTKCTL_VALID_BITS;
+			if (!cpus_have_final_cap(ARM64_HAS_NV2P1)) {
+				val &= CNTKCTL_VALID_BITS;
+				val |= __vcpu_sys_reg(vcpu, reg) & ~CNTKCTL_VALID_BITS;
+			}
 			return val;
 		case CPTR_EL2:
 			if (cpus_have_final_cap(ARM64_HAS_NV2P1))
-- 
2.47.3