[PATCH v2 06/15] KVM: arm64: nv: Handle ZCR_EL2 traps

Oliver Upton
2024-06-13T20:18:42Z

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@linux.dev>
---
arch/arm64/include/asm/kvm_emulate.h | 8 ++++++
arch/arm64/include/asm/kvm_host.h | 3 +++
arch/arm64/kvm/sys_regs.c | 38 ++++++++++++++++++++++++++++
3 files changed, 49 insertions(+)

diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
index cc5c93b46e6f..15c70f1ebeb3 100644
--- a/arch/arm64/include/asm/kvm_emulate.h
+++ b/arch/arm64/include/asm/kvm_emulate.h
@@ -56,6 +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)
{
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..80aa99a012ae 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 +2200,40 @@ 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
@@ -2688,6 +2723,9 @@ 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),
--
2.45.2.627.g7a2c4fd464-goog