[PATCH v4 09/29] KVM: arm64: Relax CPTR_EL2 handling when FEAT_NV2p1 is present

[Marc Zyngier <maz@kernel.org>]

With FEAT_NV2P1, it is no longer necessary to trap CPTR_EL2 accesses
via CPACR_EL1, as CPACR_EL1.TCPAC is guaranteed to be stateful.

Prevent such trapping and context switch CPACTR_EL1 in NV contexts
when NV2P1 is present.

Reviewed-by: Joey Gouly <joey.gouly@arm.com>
Reviewed-by: Yuan Yao <yaoyuan@linux.alibaba.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
---
 arch/arm64/kvm/hyp/include/hyp/switch.h | 5 +++--
 arch/arm64/kvm/hyp/vhe/switch.c         | 3 +++
 arch/arm64/kvm/hyp/vhe/sysreg-sr.c      | 8 +++++---
 arch/arm64/kvm/sys_regs.c               | 5 ++++-
 4 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/kvm/hyp/include/hyp/switch.h b/arch/arm64/kvm/hyp/include/hyp/switch.h
index 8e5f492f39086..7b27296c94607 100644
--- a/arch/arm64/kvm/hyp/include/hyp/switch.h
+++ b/arch/arm64/kvm/hyp/include/hyp/switch.h
@@ -108,9 +108,10 @@ static inline void __activate_cptr_traps_vhe(struct kvm_vcpu *vcpu)
 	 * The architecture is a bit crap (what a surprise): an EL2 guest
 	 * writing to CPTR_EL2 via CPACR_EL1 can't set any of TCPAC or TTA,
 	 * as they are RES0 in the guest's view. To work around it, trap the
-	 * sucker using the very same bit it can't set...
+	 * sucker using the very same bit it can't set. FEAT_NV2p1 fixes it.
 	 */
-	if (vcpu_el2_e2h_is_set(vcpu) && is_hyp_ctxt(vcpu))
+	if (!cpus_have_final_cap(ARM64_HAS_NV2P1) &&
+	    vcpu_el2_e2h_is_set(vcpu) && is_hyp_ctxt(vcpu))
 		val |= CPTR_EL2_TCPAC;
 
 	/*
diff --git a/arch/arm64/kvm/hyp/vhe/switch.c b/arch/arm64/kvm/hyp/vhe/switch.c
index 684cebf23aa0e..a8da40568a048 100644
--- a/arch/arm64/kvm/hyp/vhe/switch.c
+++ b/arch/arm64/kvm/hyp/vhe/switch.c
@@ -443,6 +443,9 @@ static bool kvm_hyp_handle_cpacr_el1(struct kvm_vcpu *vcpu, u64 *exit_code)
 	u64 esr = kvm_vcpu_get_esr(vcpu);
 	int rt;
 
+	if (cpus_have_final_cap(ARM64_HAS_NV2P1))
+		return false;
+
 	if (!is_hyp_ctxt(vcpu) || esr_sys64_to_sysreg(esr) != SYS_CPACR_EL1)
 		return false;
 
diff --git a/arch/arm64/kvm/hyp/vhe/sysreg-sr.c b/arch/arm64/kvm/hyp/vhe/sysreg-sr.c
index be685b63e8cf2..6f0f046e4ca4e 100644
--- a/arch/arm64/kvm/hyp/vhe/sysreg-sr.c
+++ b/arch/arm64/kvm/hyp/vhe/sysreg-sr.c
@@ -42,10 +42,12 @@ static void __sysreg_save_vel2_state(struct kvm_vcpu *vcpu)
 		u64 val;
 
 		/*
-		 * We don't save CPTR_EL2, as accesses to CPACR_EL1
-		 * are always trapped, ensuring that the in-memory
-		 * copy is always up-to-date. A small blessing...
+		 * Without FEAT_NV2p1, we don't save CPTR_EL2, as accesses
+		 * to CPACR_EL1 are always trapped, ensuring that the
+		 * in-memory copy is always up-to-date. A small blessing...
 		 */
+		if (cpus_have_final_cap(ARM64_HAS_NV2P1))
+			__vcpu_assign_sys_reg(vcpu, CPTR_EL2, read_sysreg_el1(SYS_CPACR));
 		__vcpu_assign_sys_reg(vcpu, SCTLR_EL2,	 read_sysreg_el1(SYS_SCTLR));
 		__vcpu_assign_sys_reg(vcpu, TTBR0_EL2,	 read_sysreg_el1(SYS_TTBR0));
 		__vcpu_assign_sys_reg(vcpu, TTBR1_EL2,	 read_sysreg_el1(SYS_TTBR1));
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 6b47d936efb32..1dfc1f88bec82 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -326,7 +326,10 @@ u64 vcpu_read_sys_reg(const struct kvm_vcpu *vcpu, enum vcpu_sysreg reg)
 			val |= __vcpu_sys_reg(vcpu, reg) & ~CNTKCTL_VALID_BITS;
 			return val;
 		case CPTR_EL2:
-			return __vcpu_sys_reg(vcpu, reg);
+			if (cpus_have_final_cap(ARM64_HAS_NV2P1))
+				return read_sysreg_el1(SYS_CPACR);
+			else
+				return __vcpu_sys_reg(vcpu, reg);
 		default:
 			WARN_ON_ONCE(1);
 		}
-- 
2.47.3