[RFC PATCH v3 15/16] KVM: arm64: Enable SPE for guests

[Alexandru Elisei]

We have all the bits in place to expose SPE to guests, allow userspace to
set the feature and advertise the presence of SPE in the ID_AA64DFR0_EL1
register.

Signed-off-by: Alexandru Elisei <alexandru.elisei at arm.com>
---
 arch/arm64/include/asm/kvm_host.h | 2 +-
 arch/arm64/kvm/sys_regs.c         | 8 ++++++--
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index bcecc6224c59..e5504c9847fc 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -39,7 +39,7 @@
 
 #define KVM_MAX_VCPUS VGIC_V3_MAX_CPUS
 
-#define KVM_VCPU_MAX_FEATURES 7
+#define KVM_VCPU_MAX_FEATURES 8
 
 #define KVM_REQ_SLEEP \
 	KVM_ARCH_REQ_FLAGS(0, KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP)
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 3a0687602839..076be04d2e28 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1178,8 +1178,12 @@ static u64 read_id_reg(const struct kvm_vcpu *vcpu,
 		val = cpuid_feature_cap_perfmon_field(val,
 						ID_AA64DFR0_PMUVER_SHIFT,
 						ID_AA64DFR0_PMUVER_8_1);
-		/* Don't advertise SPE to guests */
-		val &= ~(0xfUL << ID_AA64DFR0_PMSVER_SHIFT);
+		/*
+		 * Don't advertise SPE to guests without SPE. Otherwise, allow
+		 * the guest to detect the hardware SPE version.
+		 */
+		if (!vcpu_has_spe(vcpu))
+			val &= ~(0xfUL << ID_AA64DFR0_PMSVER_SHIFT);
 	} else if (id == SYS_ID_DFR0_EL1) {
 		/* Limit guests to PMUv3 for ARMv8.1 */
 		val = cpuid_feature_cap_perfmon_field(val,
-- 
2.29.1