Merge branch kvm-arm64/nv-sve into kvmarm/next

* kvm-arm64/nv-sve:
  : CPTR_EL2, FPSIMD/SVE support for nested
  :
  : This series brings support for honoring the guest hypervisor's CPTR_EL2
  : trap configuration when running a nested guest, along with support for
  : FPSIMD/SVE usage at L1 and L2.
  KVM: arm64: Allow the use of SVE+NV
  KVM: arm64: nv: Add additional trap setup for CPTR_EL2
  KVM: arm64: nv: Add trap description for CPTR_EL2
  KVM: arm64: nv: Add TCPAC/TTA to CPTR->CPACR conversion helper
  KVM: arm64: nv: Honor guest hypervisor's FP/SVE traps in CPTR_EL2
  KVM: arm64: nv: Load guest FP state for ZCR_EL2 trap
  KVM: arm64: nv: Handle CPACR_EL1 traps
  KVM: arm64: Spin off helper for programming CPTR traps
  KVM: arm64: nv: Ensure correct VL is loaded before saving SVE state
  KVM: arm64: nv: Use guest hypervisor's max VL when running nested guest
  KVM: arm64: nv: Save guest's ZCR_EL2 when in hyp context
  KVM: arm64: nv: Load guest hyp's ZCR into EL1 state
  KVM: arm64: nv: Handle ZCR_EL2 traps
  KVM: arm64: nv: Forward SVE traps to guest hypervisor
  KVM: arm64: nv: Forward FP/ASIMD traps to guest hypervisor
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>

arch/arm64/include/asm/kvm_emulate.h

@@ -11,6 +11,7 @@
 #ifndef __ARM64_KVM_EMULATE_H__
 #define __ARM64_KVM_EMULATE_H__
 
+#include <linux/bitfield.h>
 #include <linux/kvm_host.h>
 
 #include <asm/debug-monitors.h>
@@ -55,6 +56,14 @@ void kvm_emulate_nested_eret(struct kvm_vcpu *vcpu);
 int kvm_inject_nested_sync(struct kvm_vcpu *vcpu, u64 esr_el2);
 int kvm_inject_nested_irq(struct kvm_vcpu *vcpu);
 
+static inline void kvm_inject_nested_sve_trap(struct kvm_vcpu *vcpu)
+{
+	u64 esr = FIELD_PREP(ESR_ELx_EC_MASK, ESR_ELx_EC_SVE) |
+		  ESR_ELx_IL;
+
+	kvm_inject_nested_sync(vcpu, esr);
+}
+
 #if defined(__KVM_VHE_HYPERVISOR__) || defined(__KVM_NVHE_HYPERVISOR__)
 static __always_inline bool vcpu_el1_is_32bit(struct kvm_vcpu *vcpu)
 {
@@ -638,4 +647,50 @@ static __always_inline void kvm_reset_cptr_el2(struct kvm_vcpu *vcpu)
 
 	kvm_write_cptr_el2(val);
 }
+
+/*
+ * Returns a 'sanitised' view of CPTR_EL2, translating from nVHE to the VHE
+ * format if E2H isn't set.
+ */
+static inline u64 vcpu_sanitised_cptr_el2(const struct kvm_vcpu *vcpu)
+{
+	u64 cptr = __vcpu_sys_reg(vcpu, CPTR_EL2);
+
+	if (!vcpu_el2_e2h_is_set(vcpu))
+		cptr = translate_cptr_el2_to_cpacr_el1(cptr);
+
+	return cptr;
+}
+
+static inline bool ____cptr_xen_trap_enabled(const struct kvm_vcpu *vcpu,
+					     unsigned int xen)
+{
+	switch (xen) {
+	case 0b00:
+	case 0b10:
+		return true;
+	case 0b01:
+		return vcpu_el2_tge_is_set(vcpu) && !vcpu_is_el2(vcpu);
+	case 0b11:
+	default:
+		return false;
+	}
+}
+
+#define __guest_hyp_cptr_xen_trap_enabled(vcpu, xen)				\
+	(!vcpu_has_nv(vcpu) ? false :						\
+	 ____cptr_xen_trap_enabled(vcpu,					\
+				   SYS_FIELD_GET(CPACR_ELx, xen,		\
+						 vcpu_sanitised_cptr_el2(vcpu))))
+
+static inline bool guest_hyp_fpsimd_traps_enabled(const struct kvm_vcpu *vcpu)
+{
+	return __guest_hyp_cptr_xen_trap_enabled(vcpu, FPEN);
+}
+
+static inline bool guest_hyp_sve_traps_enabled(const struct kvm_vcpu *vcpu)
+{
+	return __guest_hyp_cptr_xen_trap_enabled(vcpu, ZEN);
+}
+
 #endif /* __ARM64_KVM_EMULATE_H__ */

arch/arm64/include/asm/kvm_host.h

@@ -458,6 +458,7 @@ enum vcpu_sysreg {
 	MDCR_EL2,	/* Monitor Debug Configuration Register (EL2) */
 	CPTR_EL2,	/* Architectural Feature Trap Register (EL2) */
 	HACR_EL2,	/* Hypervisor Auxiliary Control Register */
+	ZCR_EL2,	/* SVE Control Register (EL2) */
 	TTBR0_EL2,	/* Translation Table Base Register 0 (EL2) */
 	TTBR1_EL2,	/* Translation Table Base Register 1 (EL2) */
 	TCR_EL2,	/* Translation Control Register (EL2) */
@@ -902,6 +903,9 @@ struct kvm_vcpu_arch {
 
 #define vcpu_sve_max_vq(vcpu)	sve_vq_from_vl((vcpu)->arch.sve_max_vl)
 
+#define vcpu_sve_zcr_elx(vcpu)						\
+	(unlikely(is_hyp_ctxt(vcpu)) ? ZCR_EL2 : ZCR_EL1)
+
 #define vcpu_sve_state_size(vcpu) ({					\
 	size_t __size_ret;						\
 	unsigned int __vcpu_vq;						\
@@ -1026,6 +1030,7 @@ static inline bool __vcpu_read_sys_reg_from_cpu(int reg, u64 *val)
 	case DACR32_EL2:	*val = read_sysreg_s(SYS_DACR32_EL2);	break;
 	case IFSR32_EL2:	*val = read_sysreg_s(SYS_IFSR32_EL2);	break;
 	case DBGVCR32_EL2:	*val = read_sysreg_s(SYS_DBGVCR32_EL2);	break;
+	case ZCR_EL1:		*val = read_sysreg_s(SYS_ZCR_EL12);	break;
 	default:		return false;
 	}
 
@@ -1071,6 +1076,7 @@ static inline bool __vcpu_write_sys_reg_to_cpu(u64 val, int reg)
 	case DACR32_EL2:	write_sysreg_s(val, SYS_DACR32_EL2);	break;
 	case IFSR32_EL2:	write_sysreg_s(val, SYS_IFSR32_EL2);	break;
 	case DBGVCR32_EL2:	write_sysreg_s(val, SYS_DBGVCR32_EL2);	break;
+	case ZCR_EL1:		write_sysreg_s(val, SYS_ZCR_EL12);	break;
 	default:		return false;
 	}
 

arch/arm64/include/asm/kvm_nested.h

@@ -33,7 +33,7 @@ static inline u64 translate_tcr_el2_to_tcr_el1(u64 tcr)
 
 static inline u64 translate_cptr_el2_to_cpacr_el1(u64 cptr_el2)
 {
-	u64 cpacr_el1 = 0;
+	u64 cpacr_el1 = CPACR_ELx_RES1;
 
 	if (cptr_el2 & CPTR_EL2_TTA)
 		cpacr_el1 |= CPACR_ELx_TTA;
@@ -42,6 +42,8 @@ static inline u64 translate_cptr_el2_to_cpacr_el1(u64 cptr_el2)
 	if (!(cptr_el2 & CPTR_EL2_TZ))
 		cpacr_el1 |= CPACR_ELx_ZEN;
 
+	cpacr_el1 |= cptr_el2 & (CPTR_EL2_TCPAC | CPTR_EL2_TAM);
+
 	return cpacr_el1;
 }
 

arch/arm64/kvm/arm.c

@@ -1458,11 +1458,6 @@ static int kvm_vcpu_init_check_features(struct kvm_vcpu *vcpu,
 	    test_bit(KVM_ARM_VCPU_PTRAUTH_GENERIC, &features))
 		return -EINVAL;
 
-	/* Disallow NV+SVE for the time being */
-	if (test_bit(KVM_ARM_VCPU_HAS_EL2, &features) &&
-	    test_bit(KVM_ARM_VCPU_SVE, &features))
-		return -EINVAL;
-
 	if (!test_bit(KVM_ARM_VCPU_EL1_32BIT, &features))
 		return 0;
 

arch/arm64/kvm/emulate-nested.c

@@ -79,6 +79,10 @@ enum cgt_group_id {
 	CGT_MDCR_E2TB,
 	CGT_MDCR_TDCC,
 
+	CGT_CPACR_E0POE,
+	CGT_CPTR_TAM,
+	CGT_CPTR_TCPAC,
+
 	/*
 	 * Anything after this point is a combination of coarse trap
 	 * controls, which must all be evaluated to decide what to do.
@@ -106,6 +110,8 @@ enum cgt_group_id {
 	CGT_CNTHCTL_EL1PCTEN = __COMPLEX_CONDITIONS__,
 	CGT_CNTHCTL_EL1PTEN,
 
+	CGT_CPTR_TTA,
+
 	/* Must be last */
 	__NR_CGT_GROUP_IDS__
 };
@@ -345,6 +351,24 @@ static const struct trap_bits coarse_trap_bits[] = {
 		.mask		= MDCR_EL2_TDCC,
 		.behaviour	= BEHAVE_FORWARD_ANY,
 	},
+	[CGT_CPACR_E0POE] = {
+		.index		= CPTR_EL2,
+		.value		= CPACR_ELx_E0POE,
+		.mask		= CPACR_ELx_E0POE,
+		.behaviour	= BEHAVE_FORWARD_ANY,
+	},
+	[CGT_CPTR_TAM] = {
+		.index		= CPTR_EL2,
+		.value		= CPTR_EL2_TAM,
+		.mask		= CPTR_EL2_TAM,
+		.behaviour	= BEHAVE_FORWARD_ANY,
+	},
+	[CGT_CPTR_TCPAC] = {
+		.index		= CPTR_EL2,
+		.value		= CPTR_EL2_TCPAC,
+		.mask		= CPTR_EL2_TCPAC,
+		.behaviour	= BEHAVE_FORWARD_ANY,
+	},
 };
 
 #define MCB(id, ...)						\
@@ -410,12 +434,26 @@ static enum trap_behaviour check_cnthctl_el1pten(struct kvm_vcpu *vcpu)
 	return BEHAVE_FORWARD_ANY;
 }
 
+static enum trap_behaviour check_cptr_tta(struct kvm_vcpu *vcpu)
+{
+	u64 val = __vcpu_sys_reg(vcpu, CPTR_EL2);
+
+	if (!vcpu_el2_e2h_is_set(vcpu))
+		val = translate_cptr_el2_to_cpacr_el1(val);
+
+	if (val & CPACR_ELx_TTA)
+		return BEHAVE_FORWARD_ANY;
+
+	return BEHAVE_HANDLE_LOCALLY;
+}
+
 #define CCC(id, fn)				\
 	[id - __COMPLEX_CONDITIONS__] = fn
 
 static const complex_condition_check ccc[] = {
 	CCC(CGT_CNTHCTL_EL1PCTEN, check_cnthctl_el1pcten),
 	CCC(CGT_CNTHCTL_EL1PTEN, check_cnthctl_el1pten),
+	CCC(CGT_CPTR_TTA, check_cptr_tta),
 };
 
 /*
@@ -1000,6 +1038,59 @@ static const struct encoding_to_trap_config encoding_to_cgt[] __initconst = {
 	SR_TRAP(SYS_TRBPTR_EL1, 	CGT_MDCR_E2TB),
 	SR_TRAP(SYS_TRBSR_EL1, 		CGT_MDCR_E2TB),
 	SR_TRAP(SYS_TRBTRG_EL1,		CGT_MDCR_E2TB),
+	SR_TRAP(SYS_CPACR_EL1,		CGT_CPTR_TCPAC),
+	SR_TRAP(SYS_AMUSERENR_EL0,	CGT_CPTR_TAM),
+	SR_TRAP(SYS_AMCFGR_EL0,		CGT_CPTR_TAM),
+	SR_TRAP(SYS_AMCGCR_EL0,		CGT_CPTR_TAM),
+	SR_TRAP(SYS_AMCNTENCLR0_EL0,	CGT_CPTR_TAM),
+	SR_TRAP(SYS_AMCNTENCLR1_EL0,	CGT_CPTR_TAM),
+	SR_TRAP(SYS_AMCNTENSET0_EL0,	CGT_CPTR_TAM),
+	SR_TRAP(SYS_AMCNTENSET1_EL0,	CGT_CPTR_TAM),
+	SR_TRAP(SYS_AMCR_EL0,		CGT_CPTR_TAM),
+	SR_TRAP(SYS_AMEVCNTR0_EL0(0),	CGT_CPTR_TAM),
+	SR_TRAP(SYS_AMEVCNTR0_EL0(1),	CGT_CPTR_TAM),
+	SR_TRAP(SYS_AMEVCNTR0_EL0(2),	CGT_CPTR_TAM),
+	SR_TRAP(SYS_AMEVCNTR0_EL0(3),	CGT_CPTR_TAM),
+	SR_TRAP(SYS_AMEVCNTR1_EL0(0),	CGT_CPTR_TAM),
+	SR_TRAP(SYS_AMEVCNTR1_EL0(1),	CGT_CPTR_TAM),
+	SR_TRAP(SYS_AMEVCNTR1_EL0(2),	CGT_CPTR_TAM),
+	SR_TRAP(SYS_AMEVCNTR1_EL0(3),	CGT_CPTR_TAM),
+	SR_TRAP(SYS_AMEVCNTR1_EL0(4),	CGT_CPTR_TAM),
+	SR_TRAP(SYS_AMEVCNTR1_EL0(5),	CGT_CPTR_TAM),
+	SR_TRAP(SYS_AMEVCNTR1_EL0(6),	CGT_CPTR_TAM),
+	SR_TRAP(SYS_AMEVCNTR1_EL0(7),	CGT_CPTR_TAM),
+	SR_TRAP(SYS_AMEVCNTR1_EL0(8),	CGT_CPTR_TAM),
+	SR_TRAP(SYS_AMEVCNTR1_EL0(9),	CGT_CPTR_TAM),
+	SR_TRAP(SYS_AMEVCNTR1_EL0(10),	CGT_CPTR_TAM),
+	SR_TRAP(SYS_AMEVCNTR1_EL0(11),	CGT_CPTR_TAM),
+	SR_TRAP(SYS_AMEVCNTR1_EL0(12),	CGT_CPTR_TAM),
+	SR_TRAP(SYS_AMEVCNTR1_EL0(13),	CGT_CPTR_TAM),
+	SR_TRAP(SYS_AMEVCNTR1_EL0(14),	CGT_CPTR_TAM),
+	SR_TRAP(SYS_AMEVCNTR1_EL0(15),	CGT_CPTR_TAM),
+	SR_TRAP(SYS_AMEVTYPER0_EL0(0),	CGT_CPTR_TAM),
+	SR_TRAP(SYS_AMEVTYPER0_EL0(1),	CGT_CPTR_TAM),
+	SR_TRAP(SYS_AMEVTYPER0_EL0(2),	CGT_CPTR_TAM),
+	SR_TRAP(SYS_AMEVTYPER0_EL0(3),	CGT_CPTR_TAM),
+	SR_TRAP(SYS_AMEVTYPER1_EL0(0),	CGT_CPTR_TAM),
+	SR_TRAP(SYS_AMEVTYPER1_EL0(1),	CGT_CPTR_TAM),
+	SR_TRAP(SYS_AMEVTYPER1_EL0(2),	CGT_CPTR_TAM),
+	SR_TRAP(SYS_AMEVTYPER1_EL0(3),	CGT_CPTR_TAM),
+	SR_TRAP(SYS_AMEVTYPER1_EL0(4),	CGT_CPTR_TAM),
+	SR_TRAP(SYS_AMEVTYPER1_EL0(5),	CGT_CPTR_TAM),
+	SR_TRAP(SYS_AMEVTYPER1_EL0(6),	CGT_CPTR_TAM),
+	SR_TRAP(SYS_AMEVTYPER1_EL0(7),	CGT_CPTR_TAM),
+	SR_TRAP(SYS_AMEVTYPER1_EL0(8),	CGT_CPTR_TAM),
+	SR_TRAP(SYS_AMEVTYPER1_EL0(9),	CGT_CPTR_TAM),
+	SR_TRAP(SYS_AMEVTYPER1_EL0(10),	CGT_CPTR_TAM),
+	SR_TRAP(SYS_AMEVTYPER1_EL0(11),	CGT_CPTR_TAM),
+	SR_TRAP(SYS_AMEVTYPER1_EL0(12),	CGT_CPTR_TAM),
+	SR_TRAP(SYS_AMEVTYPER1_EL0(13),	CGT_CPTR_TAM),
+	SR_TRAP(SYS_AMEVTYPER1_EL0(14),	CGT_CPTR_TAM),
+	SR_TRAP(SYS_AMEVTYPER1_EL0(15),	CGT_CPTR_TAM),
+	SR_TRAP(SYS_POR_EL0,		CGT_CPACR_E0POE),
+	/* op0=2, op1=1, and CRn<0b1000 */
+	SR_RANGE_TRAP(sys_reg(2, 1, 0, 0, 0),
+		      sys_reg(2, 1, 7, 15, 7), CGT_CPTR_TTA),
 	SR_TRAP(SYS_CNTP_TVAL_EL0,	CGT_CNTHCTL_EL1PTEN),
 	SR_TRAP(SYS_CNTP_CVAL_EL0,	CGT_CNTHCTL_EL1PTEN),
 	SR_TRAP(SYS_CNTP_CTL_EL0,	CGT_CNTHCTL_EL1PTEN),

arch/arm64/kvm/fpsimd.c

@@ -178,7 +178,13 @@ void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu)
 
 	if (guest_owns_fp_regs()) {
 		if (vcpu_has_sve(vcpu)) {
-			__vcpu_sys_reg(vcpu, ZCR_EL1) = read_sysreg_el1(SYS_ZCR);
+			u64 zcr = read_sysreg_el1(SYS_ZCR);
+
+			/*
+			 * If the vCPU is in the hyp context then ZCR_EL1 is
+			 * loaded with its vEL2 counterpart.
+			 */
+			__vcpu_sys_reg(vcpu, vcpu_sve_zcr_elx(vcpu)) = zcr;
 
 			/*
 			 * Restore the VL that was saved when bound to the CPU,
@@ -189,11 +195,14 @@ void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu)
 			 * Note that this means that at guest exit ZCR_EL1 is
 			 * not necessarily the same as on guest entry.
 			 *
-			 * Restoring the VL isn't needed in VHE mode since
-			 * ZCR_EL2 (accessed via ZCR_EL1) would fulfill the same
-			 * role when doing the save from EL2.
+			 * ZCR_EL2 holds the guest hypervisor's VL when running
+			 * a nested guest, which could be smaller than the
+			 * max for the vCPU. Similar to above, we first need to
+			 * switch to a VL consistent with the layout of the
+			 * vCPU's SVE state. KVM support for NV implies VHE, so
+			 * using the ZCR_EL1 alias is safe.
 			 */
-			if (!has_vhe())
+			if (!has_vhe() || (vcpu_has_nv(vcpu) && !is_hyp_ctxt(vcpu)))
 				sve_cond_update_zcr_vq(vcpu_sve_max_vq(vcpu) - 1,
 						       SYS_ZCR_EL1);
 		}

arch/arm64/kvm/handle_exit.c

@@ -94,11 +94,19 @@ static int handle_smc(struct kvm_vcpu *vcpu)
 }
 
 /*
- * Guest access to FP/ASIMD registers are routed to this handler only
- * when the system doesn't support FP/ASIMD.
+ * This handles the cases where the system does not support FP/ASIMD or when
+ * we are running nested virtualization and the guest hypervisor is trapping
+ * FP/ASIMD accesses by its guest guest.
+ *
+ * All other handling of guest vs. host FP/ASIMD register state is handled in
+ * fixup_guest_exit().
  */
-static int handle_no_fpsimd(struct kvm_vcpu *vcpu)
+static int kvm_handle_fpasimd(struct kvm_vcpu *vcpu)
 {
+	if (guest_hyp_fpsimd_traps_enabled(vcpu))
+		return kvm_inject_nested_sync(vcpu, kvm_vcpu_get_esr(vcpu));
+
+	/* This is the case when the system doesn't support FP/ASIMD. */
 	kvm_inject_undefined(vcpu);
 	return 1;
 }
@@ -209,6 +217,9 @@ static int kvm_handle_unknown_ec(struct kvm_vcpu *vcpu)
  */
 static int handle_sve(struct kvm_vcpu *vcpu)
 {
+	if (guest_hyp_sve_traps_enabled(vcpu))
+		return kvm_inject_nested_sync(vcpu, kvm_vcpu_get_esr(vcpu));
+
 	kvm_inject_undefined(vcpu);
 	return 1;
 }
@@ -304,7 +315,7 @@ static exit_handle_fn arm_exit_handlers[] = {
 	[ESR_ELx_EC_BREAKPT_LOW]= kvm_handle_guest_debug,
 	[ESR_ELx_EC_BKPT32]	= kvm_handle_guest_debug,
 	[ESR_ELx_EC_BRK64]	= kvm_handle_guest_debug,
-	[ESR_ELx_EC_FP_ASIMD]	= handle_no_fpsimd,
+	[ESR_ELx_EC_FP_ASIMD]	= kvm_handle_fpasimd,
 	[ESR_ELx_EC_PAC]	= kvm_handle_ptrauth,
 };
 

arch/arm64/kvm/hyp/include/hyp/switch.h

@@ -314,11 +314,24 @@ static bool kvm_hyp_handle_mops(struct kvm_vcpu *vcpu, u64 *exit_code)
 
 static inline void __hyp_sve_restore_guest(struct kvm_vcpu *vcpu)
 {
+	/*
+	 * The vCPU's saved SVE state layout always matches the max VL of the
+	 * vCPU. Start off with the max VL so we can load the SVE state.
+	 */
 	sve_cond_update_zcr_vq(vcpu_sve_max_vq(vcpu) - 1, SYS_ZCR_EL2);
 	__sve_restore_state(vcpu_sve_pffr(vcpu),
 			    &vcpu->arch.ctxt.fp_regs.fpsr,
 			    true);
-	write_sysreg_el1(__vcpu_sys_reg(vcpu, ZCR_EL1), SYS_ZCR);
+
+	/*
+	 * The effective VL for a VM could differ from the max VL when running a
+	 * nested guest, as the guest hypervisor could select a smaller VL. Slap
+	 * that into hardware before wrapping up.
+	 */
+	if (vcpu_has_nv(vcpu) && !is_hyp_ctxt(vcpu))
+		sve_cond_update_zcr_vq(__vcpu_sys_reg(vcpu, ZCR_EL2), SYS_ZCR_EL2);
+
+	write_sysreg_el1(__vcpu_sys_reg(vcpu, vcpu_sve_zcr_elx(vcpu)), SYS_ZCR);
 }
 
 static inline void __hyp_sve_save_host(void)
@@ -354,10 +367,19 @@ static bool kvm_hyp_handle_fpsimd(struct kvm_vcpu *vcpu, u64 *exit_code)
 	/* Only handle traps the vCPU can support here: */
 	switch (esr_ec) {
 	case ESR_ELx_EC_FP_ASIMD:
+		/* Forward traps to the guest hypervisor as required */
+		if (guest_hyp_fpsimd_traps_enabled(vcpu))
+			return false;
 		break;
+	case ESR_ELx_EC_SYS64:
+		if (WARN_ON_ONCE(!is_hyp_ctxt(vcpu)))
+			return false;
+		fallthrough;
 	case ESR_ELx_EC_SVE:
 		if (!sve_guest)
 			return false;
+		if (guest_hyp_sve_traps_enabled(vcpu))
+			return false;
 		break;
 	default:
 		return false;

arch/arm64/kvm/hyp/vhe/switch.c

@@ -65,6 +65,77 @@ static u64 __compute_hcr(struct kvm_vcpu *vcpu)
 	return hcr | (__vcpu_sys_reg(vcpu, HCR_EL2) & ~NV_HCR_GUEST_EXCLUDE);
 }
 
+static void __activate_cptr_traps(struct kvm_vcpu *vcpu)
+{
+	u64 cptr;
+
+	/*
+	 * With VHE (HCR.E2H == 1), accesses to CPACR_EL1 are routed to
+	 * CPTR_EL2. In general, CPACR_EL1 has the same layout as CPTR_EL2,
+	 * except for some missing controls, such as TAM.
+	 * In this case, CPTR_EL2.TAM has the same position with or without
+	 * VHE (HCR.E2H == 1) which allows us to use here the CPTR_EL2.TAM
+	 * shift value for trapping the AMU accesses.
+	 */
+	u64 val = CPACR_ELx_TTA | CPTR_EL2_TAM;
+
+	if (guest_owns_fp_regs()) {
+		val |= CPACR_ELx_FPEN;
+		if (vcpu_has_sve(vcpu))
+			val |= CPACR_ELx_ZEN;
+	} else {
+		__activate_traps_fpsimd32(vcpu);
+	}
+
+	if (!vcpu_has_nv(vcpu))
+		goto write;
+
+	/*
+	 * 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...
+	 */
+	if (vcpu_el2_e2h_is_set(vcpu) && is_hyp_ctxt(vcpu))
+		val |= CPTR_EL2_TCPAC;
+
+	/*
+	 * Layer the guest hypervisor's trap configuration on top of our own if
+	 * we're in a nested context.
+	 */
+	if (is_hyp_ctxt(vcpu))
+		goto write;
+
+	cptr = vcpu_sanitised_cptr_el2(vcpu);
+
+	/*
+	 * Pay attention, there's some interesting detail here.
+	 *
+	 * The CPTR_EL2.xEN fields are 2 bits wide, although there are only two
+	 * meaningful trap states when HCR_EL2.TGE = 0 (running a nested guest):
+	 *
+	 *  - CPTR_EL2.xEN = x0, traps are enabled
+	 *  - CPTR_EL2.xEN = x1, traps are disabled
+	 *
+	 * In other words, bit[0] determines if guest accesses trap or not. In
+	 * the interest of simplicity, clear the entire field if the guest
+	 * hypervisor has traps enabled to dispel any illusion of something more
+	 * complicated taking place.
+	 */
+	if (!(SYS_FIELD_GET(CPACR_ELx, FPEN, cptr) & BIT(0)))
+		val &= ~CPACR_ELx_FPEN;
+	if (!(SYS_FIELD_GET(CPACR_ELx, ZEN, cptr) & BIT(0)))
+		val &= ~CPACR_ELx_ZEN;
+
+	if (kvm_has_feat(vcpu->kvm, ID_AA64MMFR3_EL1, S2POE, IMP))
+		val |= cptr & CPACR_ELx_E0POE;
+
+	val |= cptr & CPTR_EL2_TCPAC;
+
+write:
+	write_sysreg(val, cpacr_el1);
+}
+
 static void __activate_traps(struct kvm_vcpu *vcpu)
 {
 	u64 val;
@@ -91,30 +162,7 @@ static void __activate_traps(struct kvm_vcpu *vcpu)
 		}
 	}
 
-	val = read_sysreg(cpacr_el1);
-	val |= CPACR_ELx_TTA;
-	val &= ~(CPACR_ELx_ZEN | CPACR_ELx_SMEN);
-
-	/*
-	 * With VHE (HCR.E2H == 1), accesses to CPACR_EL1 are routed to
-	 * CPTR_EL2. In general, CPACR_EL1 has the same layout as CPTR_EL2,
-	 * except for some missing controls, such as TAM.
-	 * In this case, CPTR_EL2.TAM has the same position with or without
-	 * VHE (HCR.E2H == 1) which allows us to use here the CPTR_EL2.TAM
-	 * shift value for trapping the AMU accesses.
-	 */
-
-	val |= CPTR_EL2_TAM;
-
-	if (guest_owns_fp_regs()) {
-		if (vcpu_has_sve(vcpu))
-			val |= CPACR_ELx_ZEN;
-	} else {
-		val &= ~CPACR_ELx_FPEN;
-		__activate_traps_fpsimd32(vcpu);
-	}
-
-	write_sysreg(val, cpacr_el1);
+	__activate_cptr_traps(vcpu);
 
 	write_sysreg(__this_cpu_read(kvm_hyp_vector), vbar_el1);
 }
@@ -307,11 +355,63 @@ static bool kvm_hyp_handle_tlbi_el2(struct kvm_vcpu *vcpu, u64 *exit_code)
 	return true;
 }
 
+static bool kvm_hyp_handle_cpacr_el1(struct kvm_vcpu *vcpu, u64 *exit_code)
+{
+	u64 esr = kvm_vcpu_get_esr(vcpu);
+	int rt;
+
+	if (!is_hyp_ctxt(vcpu) || esr_sys64_to_sysreg(esr) != SYS_CPACR_EL1)
+		return false;
+
+	rt = kvm_vcpu_sys_get_rt(vcpu);
+
+	if ((esr & ESR_ELx_SYS64_ISS_DIR_MASK) == ESR_ELx_SYS64_ISS_DIR_READ) {
+		vcpu_set_reg(vcpu, rt, __vcpu_sys_reg(vcpu, CPTR_EL2));
+	} else {
+		vcpu_write_sys_reg(vcpu, vcpu_get_reg(vcpu, rt), CPTR_EL2);
+		__activate_cptr_traps(vcpu);
+	}
+
+	__kvm_skip_instr(vcpu);
+
+	return true;
+}
+
+static bool kvm_hyp_handle_zcr_el2(struct kvm_vcpu *vcpu, u64 *exit_code)
+{
+	u32 sysreg = esr_sys64_to_sysreg(kvm_vcpu_get_esr(vcpu));
+
+	if (!vcpu_has_nv(vcpu))
+		return false;
+
+	if (sysreg != SYS_ZCR_EL2)
+		return false;
+
+	if (guest_owns_fp_regs())
+		return false;
+
+	/*
+	 * ZCR_EL2 traps are handled in the slow path, with the expectation
+	 * that the guest's FP context has already been loaded onto the CPU.
+	 *
+	 * Load the guest's FP context and unconditionally forward to the
+	 * slow path for handling (i.e. return false).
+	 */
+	kvm_hyp_handle_fpsimd(vcpu, exit_code);
+	return false;
+}
+
 static bool kvm_hyp_handle_sysreg_vhe(struct kvm_vcpu *vcpu, u64 *exit_code)
 {
 	if (kvm_hyp_handle_tlbi_el2(vcpu, exit_code))
 		return true;
 
+	if (kvm_hyp_handle_cpacr_el1(vcpu, exit_code))
+		return true;
+
+	if (kvm_hyp_handle_zcr_el2(vcpu, exit_code))
+		return true;
+
 	return kvm_hyp_handle_sysreg(vcpu, exit_code);
 }
 

arch/arm64/kvm/nested.c

@@ -814,14 +814,13 @@ static void limit_nv_id_regs(struct kvm *kvm)
 		 NV_FTR(ISAR1, SPECRES));
 	kvm_set_vm_id_reg(kvm, SYS_ID_AA64ISAR1_EL1, val);
 
-	/* No AMU, MPAM, S-EL2, RAS or SVE */
+	/* No AMU, MPAM, S-EL2, or RAS */
 	val = kvm_read_vm_id_reg(kvm, SYS_ID_AA64PFR0_EL1);
 	val &= ~(GENMASK_ULL(55, 52)	|
 		 NV_FTR(PFR0, AMU)	|
 		 NV_FTR(PFR0, MPAM)	|
 		 NV_FTR(PFR0, SEL2)	|
 		 NV_FTR(PFR0, RAS)	|
-		 NV_FTR(PFR0, SVE)	|
 		 NV_FTR(PFR0, EL3)	|
 		 NV_FTR(PFR0, EL2)	|
 		 NV_FTR(PFR0, EL1));

arch/arm64/kvm/sys_regs.c

@@ -121,6 +121,7 @@ static bool get_el2_to_el1_mapping(unsigned int reg,
 		MAPPED_EL2_SYSREG(AMAIR_EL2,   AMAIR_EL1,   NULL	     );
 		MAPPED_EL2_SYSREG(ELR_EL2,     ELR_EL1,	    NULL	     );
 		MAPPED_EL2_SYSREG(SPSR_EL2,    SPSR_EL1,    NULL	     );
+		MAPPED_EL2_SYSREG(ZCR_EL2,     ZCR_EL1,     NULL	     );
 	default:
 		return false;
 	}
@@ -2214,6 +2215,40 @@ static u64 reset_hcr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r)
 	return __vcpu_sys_reg(vcpu, r->reg) = val;
 }
 
+static unsigned int sve_el2_visibility(const struct kvm_vcpu *vcpu,
+				       const struct sys_reg_desc *rd)
+{
+	unsigned int r;
+
+	r = el2_visibility(vcpu, rd);
+	if (r)
+		return r;
+
+	return sve_visibility(vcpu, rd);
+}
+
+static bool access_zcr_el2(struct kvm_vcpu *vcpu,
+			   struct sys_reg_params *p,
+			   const struct sys_reg_desc *r)
+{
+	unsigned int vq;
+
+	if (guest_hyp_sve_traps_enabled(vcpu)) {
+		kvm_inject_nested_sve_trap(vcpu);
+		return true;
+	}
+
+	if (!p->is_write) {
+		p->regval = vcpu_read_sys_reg(vcpu, ZCR_EL2);
+		return true;
+	}
+
+	vq = SYS_FIELD_GET(ZCR_ELx, LEN, p->regval) + 1;
+	vq = min(vq, vcpu_sve_max_vq(vcpu));
+	vcpu_write_sys_reg(vcpu, vq - 1, ZCR_EL2);
+	return true;
+}
+
 /*
  * Architected system registers.
  * Important: Must be sorted ascending by Op0, Op1, CRn, CRm, Op2
@@ -2706,6 +2741,9 @@ static const struct sys_reg_desc sys_reg_descs[] = {
 	EL2_REG_VNCR(HFGITR_EL2, reset_val, 0),
 	EL2_REG_VNCR(HACR_EL2, reset_val, 0),
 
+	{ SYS_DESC(SYS_ZCR_EL2), .access = access_zcr_el2, .reset = reset_val,
+	  .visibility = sve_el2_visibility, .reg = ZCR_EL2 },
+
 	EL2_REG_VNCR(HCRX_EL2, reset_val, 0),
 
 	EL2_REG(TTBR0_EL2, access_rw, reset_val, 0),