[PATCH v4 06/29] KVM: arm64: Classify CPTR_EL2 as a SR_LOC_SPECIAL register

It may not be obvious unless you look at it closely, but CPTR_EL2
is treated very differently from other registers. It is one the
registers that, despite looking very similar between EL1 and EL2
when E2H==1, have RES0 bits that get in the way.

Make it clear that CPTR_EL2 is odd by classifying it as SR_LOC_SPECIAL,
just like CNTHCTL_EL2 (and for the same reasons). This makes it
possible to use vcpu_read_sys_reg() with it, and will be necessary
once we support FEAT_NV2P1.

Reviewed-by: Joey Gouly <[email protected]>
Reviewed-by: Yuan Yao <[email protected]>
Signed-off-by: Marc Zyngier <[email protected]>
---
 arch/arm64/include/asm/kvm_emulate.h |  2 +-
 arch/arm64/kvm/sys_regs.c            | 20 ++++++++++++++++++--
 2 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
index 5bf3d7e1d92c7..9831166695186 100644
--- a/arch/arm64/include/asm/kvm_emulate.h
+++ b/arch/arm64/include/asm/kvm_emulate.h
@@ -617,7 +617,7 @@ static __always_inline void kvm_incr_pc(struct kvm_vcpu *vcpu)
  */
 static inline u64 vcpu_sanitised_cptr_el2(const struct kvm_vcpu *vcpu)
 {
-	u64 cptr = __vcpu_sys_reg(vcpu, CPTR_EL2);
+	u64 cptr = vcpu_read_sys_reg(vcpu, CPTR_EL2);
 
 	if (!vcpu_el2_e2h_is_set(vcpu))
 		cptr = translate_cptr_el2_to_cpacr_el1(cptr);
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 5d5c579d45790..6b47d936efb32 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -183,8 +183,6 @@ static void locate_register(const struct kvm_vcpu *vcpu, enum vcpu_sysreg reg,
 	switch (reg) {
 		MAPPED_EL2_SYSREG(SCTLR_EL2,   SCTLR_EL1,
 				  translate_sctlr_el2_to_sctlr_el1	     );
-		MAPPED_EL2_SYSREG(CPTR_EL2,    CPACR_EL1,
-				  translate_cptr_el2_to_cpacr_el1	     );
 		MAPPED_EL2_SYSREG(TTBR0_EL2,   TTBR0_EL1,
 				  translate_ttbr0_el2_to_ttbr0_el1	     );
 		MAPPED_EL2_SYSREG(TTBR1_EL2,   TTBR1_EL1,   NULL	     );
@@ -210,6 +208,19 @@ static void locate_register(const struct kvm_vcpu *vcpu, enum vcpu_sysreg reg,
 		loc->loc = ((is_hyp_ctxt(vcpu) && vcpu_el2_e2h_is_set(vcpu)) ?
 			    SR_LOC_SPECIAL : SR_LOC_MEMORY);
 		break;
+	case CPTR_EL2:
+		/*
+		 * CPTR_EL2 is just as special, and needs a certain amount
+		 * of handholding. It always lives in memory, due to being
+		 * heavily trapped thanks to CPACR_EL1.TCPAC being RES0.
+		 * FEAT_NV2p1 fixes this.
+		 */
+		locate_mapped_el2_register(vcpu, CPTR_EL2, CPACR_EL1,
+					   translate_cptr_el2_to_cpacr_el1,
+					   loc);
+		if (is_hyp_ctxt(vcpu) && vcpu_el2_e2h_is_set(vcpu))
+			loc->loc = SR_LOC_SPECIAL;
+		break;
 	default:
 		loc->loc = locate_direct_register(vcpu, reg);
 	}
@@ -314,6 +325,8 @@ u64 vcpu_read_sys_reg(const struct kvm_vcpu *vcpu, enum vcpu_sysreg reg)
 			val &= CNTKCTL_VALID_BITS;
 			val |= __vcpu_sys_reg(vcpu, reg) & ~CNTKCTL_VALID_BITS;
 			return val;
+		case CPTR_EL2:
+			return __vcpu_sys_reg(vcpu, reg);
 		default:
 			WARN_ON_ONCE(1);
 		}
@@ -359,6 +372,9 @@ void vcpu_write_sys_reg(struct kvm_vcpu *vcpu, u64 val, enum vcpu_sysreg reg)
 			 */
 			write_sysreg_el1(val, SYS_CNTKCTL);
 			break;
+		case CPTR_EL2:
+			write_sysreg_el1(val, SYS_CPACR);
+			break;
 		default:
 			WARN_ON_ONCE(1);
 		}
-- 
2.47.3