arm64: Add basic SVE support

This patch adds an --sve command line option to allow the Scalable
Vector Extension to be enabled when creating a guest.

This requires use of the new KVM_ARM_VCPU_FINALIZE ioctl before the
vcpu is runnable, so a new hook kvm_cpu__configure_features() is
added to provide an appropiate place to do this work.

The kernel does not enable SVE by default, and for now kvmtool
adopts the same policy: without --sve, SVE is not enabled for the
guest even if the host supports it.
Signed-off-by: Dave Martin <Dave.Martin@arm.com>

arm/aarch32/include/kvm/kvm-cpu-arch.h

@@ -13,4 +13,9 @@
 #define ARM_CPU_ID		0, 0, 0
 #define ARM_CPU_ID_MPIDR	5
 
+static inline int kvm_cpu__configure_features(struct kvm_cpu *vcpu)
+{
+	return 0;
+}
+
 #endif /* KVM__KVM_CPU_ARCH_H */

arm/aarch64/include/kvm/kvm-config-arch.h

@@ -8,7 +8,9 @@
 			"Create PMUv3 device"),				\
 	OPT_U64('\0', "kaslr-seed", &(cfg)->kaslr_seed,			\
 			"Specify random seed for Kernel Address Space "	\
-			"Layout Randomization (KASLR)"),
+			"Layout Randomization (KASLR)"),		\
+	OPT_BOOLEAN('\0', "sve", &(cfg)->has_sve,			\
+			"Enable SVE for the guest"),
 
 #include "arm-common/kvm-config-arch.h"
 

arm/aarch64/include/kvm/kvm-cpu-arch.h

@@ -8,13 +8,18 @@
 #define ARM_VCPU_FEATURE_FLAGS(kvm, cpuid)	{				\
 	[0] = ((!!(cpuid) << KVM_ARM_VCPU_POWER_OFF) |				\
 	       (!!(kvm)->cfg.arch.aarch32_guest << KVM_ARM_VCPU_EL1_32BIT) |	\
-	       (!!(kvm)->cfg.arch.has_pmuv3 << KVM_ARM_VCPU_PMU_V3))		\
+	       (!!(kvm)->cfg.arch.has_pmuv3 << KVM_ARM_VCPU_PMU_V3) |		\
+	       (!!(kvm)->cfg.arch.has_sve << KVM_ARM_VCPU_SVE))			\
 }
 
+
+
 #define ARM_MPIDR_HWID_BITMASK	0xFF00FFFFFFUL
 #define ARM_CPU_ID		3, 0, 0, 0
 #define ARM_CPU_ID_MPIDR	5
 #define ARM_CPU_CTRL		3, 0, 1, 0
 #define ARM_CPU_CTRL_SCTLR_EL1	0
 
+int kvm_cpu__configure_features(struct kvm_cpu *vcpu);
+
 #endif /* KVM__KVM_CPU_ARCH_H */

arm/aarch64/kvm-cpu.c

@@ -128,6 +128,25 @@ static void reset_vcpu_aarch64(struct kvm_cpu *vcpu)
 	}
 }
 
+static int configure_sve(struct kvm_cpu *vcpu)
+{
+	int feature = KVM_ARM_VCPU_SVE;
+
+	if (ioctl(vcpu->vcpu_fd, KVM_ARM_VCPU_FINALIZE, &feature))
+		return -1;
+
+	return 0;
+}
+
+int kvm_cpu__configure_features(struct kvm_cpu *vcpu)
+{
+	if (vcpu->kvm->cfg.arch.has_sve)
+		if (configure_sve(vcpu))
+			return -1;
+
+	return 0;
+}
+
 void kvm_cpu__reset_vcpu(struct kvm_cpu *vcpu)
 {
 	if (vcpu->kvm->cfg.arch.aarch32_guest)

arm/include/arm-common/kvm-config-arch.h

@@ -12,6 +12,7 @@ struct kvm_config_arch {
 	u64		kaslr_seed;
 	enum irqchip_type irqchip;
 	u64		fw_addr;
+	bool		has_sve;
 };
 
 int irqchip_parser(const struct option *opt, const char *arg, int unset);

arm/kvm-cpu.c

@@ -122,6 +122,9 @@ struct kvm_cpu *kvm_cpu__arch_init(struct kvm *kvm, unsigned long cpu_id)
 	vcpu->cpu_compatible	= target->compatible;
 	vcpu->is_running	= true;
 
+	if (kvm_cpu__configure_features(vcpu))
+		die("Unable to configure requested vcpu features");
+
 	return vcpu;
 }