irqchip/gic-v4.1: Disable vSGI upon (GIC CPUIF < v4.1) detection

GIC CPU interfaces versions predating GIC v4.1 were not built to
accommodate vINTID within the vSGI range; as reported in the GIC
specifications (8.2 "Changes to the CPU interface"), it is
CONSTRAINED UNPREDICTABLE to deliver a vSGI to a PE with
ID_AA64PFR0_EL1.GIC < b0011.

Check the GIC CPUIF version by reading the SYS_ID_AA64_PFR0_EL1.

Disable vSGIs if a CPUIF version < 4.1 is detected to prevent using
vSGIs on systems where they may misbehave.

Signed-off-by: Lorenzo Pieralisi <[e-mail]>
Cc: Marc Zyngier <[e-mail]>
Signed-off-by: Marc Zyngier <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

arch/arm64/kvm/vgic/vgic-mmio-v3.c

···
 		}
 		break;
 	case GICD_TYPER2:
-		if (kvm_vgic_global_state.has_gicv4_1)
+		if (kvm_vgic_global_state.has_gicv4_1 && gic_cpuif_has_vsgi())
 			value = GICD_TYPER2_nASSGIcap;
 		break;
 	case GICD_IIDR:
···
 		dist->enabled = val & GICD_CTLR_ENABLE_SS_G1;
 
 		/* Not a GICv4.1? No HW SGIs */
-		if (!kvm_vgic_global_state.has_gicv4_1)
+		if (!kvm_vgic_global_state.has_gicv4_1 || !gic_cpuif_has_vsgi())
 			val &= ~GICD_CTLR_nASSGIreq;
 
 		/* Dist stays enabled? nASSGIreq is RO */

drivers/irqchip/irq-gic-v4.c

···
 static const struct irq_domain_ops *vpe_domain_ops;
 static const struct irq_domain_ops *sgi_domain_ops;
 
+#ifdef CONFIG_ARM64
+#include <asm/cpufeature.h>
+
+bool gic_cpuif_has_vsgi(void)
+{
+	unsigned long fld, reg = read_sanitised_ftr_reg(SYS_ID_AA64PFR0_EL1);
+
+	fld = cpuid_feature_extract_unsigned_field(reg, ID_AA64PFR0_GIC_SHIFT);
+
+	return fld >= 0x3;
+}
+#else
+bool gic_cpuif_has_vsgi(void)
+{
+	return false;
+}
+#endif
+
 static bool has_v4_1(void)
 {
 	return !!sgi_domain_ops;
+}
+
+static bool has_v4_1_sgi(void)
+{
+	return has_v4_1() && gic_cpuif_has_vsgi();
 }
 
 static int its_alloc_vcpu_sgis(struct its_vpe *vpe, int idx)
···
 	char *name;
 	int sgi_base;
 
-	if (!has_v4_1())
+	if (!has_v4_1_sgi())
 		return 0;
 
 	name = kasprintf(GFP_KERNEL, "GICv4-sgi-%d", task_pid_nr(current));
···
 {
 	int i;
 
-	if (!has_v4_1())
+	if (!has_v4_1_sgi())
 		return;
 
 	for (i = 0; i < vm->nr_vpes; i++) {

include/linux/irqchip/arm-gic-v4.h

···
 		const struct irq_domain_ops *vpe_ops,
 		const struct irq_domain_ops *sgi_ops);
 
+bool gic_cpuif_has_vsgi(void);
+
 #endif