[PATCH 05/11] KVM: arm64: nv: Handle ZCR_EL2 traps

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Unlike other SVE-related registers, ZCR_EL2 takes a sysreg trap to EL2
when HCR_EL2.NV = 1. KVM still needs to honor the guest hypervisor's
trap configuration, which expects an SVE trap (i.e. ESR_EL2.EC = 0x19)
when CPTR traps are enabled for the vCPU's current context.

Otherwise, if the guest hypervisor has traps disabled, emulate the
access by mapping the requested VL into ZCR_EL1.

Signed-off-by: Oliver Upton <oliver.upton@xxxxxxxxx>
---
Notes, because I'm too lazy to respin before sending on a Friday:

 - I'll want to add a helper for synthesizing the SVE trap, open-coding
   it in the sysreg handler is gross.

 - The sysreg handler needs to check CPACR_ELx_FPEN in addition to _ZEN,
   like what I have now.

 arch/arm64/include/asm/kvm_host.h |  3 +++
 arch/arm64/kvm/sys_regs.c         | 40 +++++++++++++++++++++++++++++++
 2 files changed, 43 insertions(+)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index e01e6de414f1..aeb1c567dfad 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -422,6 +422,7 @@ 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) */
@@ -972,6 +973,7 @@ 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;
 	}
 
@@ -1017,6 +1019,7 @@ 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;
 	}
 
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 22b45a15d068..a662e9d2d917 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/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;
 	}
@@ -2199,6 +2200,42 @@ 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)
+{
+	u64 esr = FIELD_PREP(ESR_ELx_EC_MASK, ESR_ELx_EC_SVE) |
+		  ESR_ELx_IL;
+	unsigned int vq;
+
+	if (guest_hyp_sve_traps_enabled(vcpu)) {
+		kvm_inject_nested_sync(vcpu, esr);
+		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
@@ -2688,6 +2725,9 @@ 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),
-- 
2.45.1.288.g0e0cd299f1-goog





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