powerpc/xive: add XIVE Exploitation Mode to CAS

On POWER9, the Client Architecture Support (CAS) negotiation process
determines whether the guest operates in XIVE Legacy compatibility or
in XIVE exploitation mode. Now that we have initial guest support for
the XIVE interrupt controller, let's inform the hypervisor what we can
do.

The platform advertises the XIVE Exploitation Mode support using the
property "ibm,arch-vec-5-platform-support-vec-5", byte 23 bits 0-1 :

 - 0b00 XIVE legacy mode Only
 - 0b01 XIVE exploitation mode Only
 - 0b10 XIVE legacy or exploitation mode

The OS asks for XIVE Exploitation Mode support using the property
"ibm,architecture-vec-5", byte 23 bits 0-1:

 - 0b00 XIVE legacy mode Only
 - 0b01 XIVE exploitation mode Only
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/asm/prom.h

@@ -159,7 +159,10 @@ struct of_drconf_cell {
 #define OV5_PFO_HW_842		0x1140	/* PFO Compression Accelerator */
 #define OV5_PFO_HW_ENCR		0x1120	/* PFO Encryption Accelerator */
 #define OV5_SUB_PROCESSORS	0x1501	/* 1,2,or 4 Sub-Processors supported */
-#define OV5_XIVE_EXPLOIT	0x1701	/* XIVE exploitation supported */
+#define OV5_XIVE_SUPPORT	0x17C0	/* XIVE Exploitation Support Mask */
+#define OV5_XIVE_LEGACY		0x1700	/* XIVE legacy mode Only */
+#define OV5_XIVE_EXPLOIT	0x1740	/* XIVE exploitation mode Only */
+#define OV5_XIVE_EITHER		0x1780	/* XIVE legacy or exploitation mode */
 /* MMU Base Architecture */
 #define OV5_MMU_SUPPORT		0x18C0	/* MMU Mode Support Mask */
 #define OV5_MMU_HASH		0x1800	/* Hash MMU Only */

arch/powerpc/kernel/prom_init.c

@@ -177,6 +177,7 @@ struct platform_support {
 	bool hash_mmu;
 	bool radix_mmu;
 	bool radix_gtse;
+	bool xive;
 };
 
 /* Platforms codes are now obsolete in the kernel. Now only used within this
@@ -1041,6 +1042,27 @@ static void __init prom_parse_mmu_model(u8 val,
 	}
 }
 
+static void __init prom_parse_xive_model(u8 val,
+					 struct platform_support *support)
+{
+	switch (val) {
+	case OV5_FEAT(OV5_XIVE_EITHER): /* Either Available */
+		prom_debug("XIVE - either mode supported\n");
+		support->xive = true;
+		break;
+	case OV5_FEAT(OV5_XIVE_EXPLOIT): /* Only Exploitation mode */
+		prom_debug("XIVE - exploitation mode supported\n");
+		support->xive = true;
+		break;
+	case OV5_FEAT(OV5_XIVE_LEGACY): /* Only Legacy mode */
+		prom_debug("XIVE - legacy mode supported\n");
+		break;
+	default:
+		prom_debug("Unknown xive support option: 0x%x\n", val);
+		break;
+	}
+}
+
 static void __init prom_parse_platform_support(u8 index, u8 val,
 					       struct platform_support *support)
 {
@@ -1054,6 +1076,10 @@ static void __init prom_parse_platform_support(u8 index, u8 val,
 			support->radix_gtse = true;
 		}
 		break;
+	case OV5_INDX(OV5_XIVE_SUPPORT): /* Interrupt mode */
+		prom_parse_xive_model(val & OV5_FEAT(OV5_XIVE_SUPPORT),
+				      support);
+		break;
 	}
 }
 
@@ -1062,7 +1088,8 @@ static void __init prom_check_platform_support(void)
 	struct platform_support supported = {
 		.hash_mmu = false,
 		.radix_mmu = false,
-		.radix_gtse = false
+		.radix_gtse = false,
+		.xive = false
 	};
 	int prop_len = prom_getproplen(prom.chosen,
 				       "ibm,arch-vec-5-platform-support");
@@ -1095,6 +1122,11 @@ static void __init prom_check_platform_support(void)
 		/* We're probably on a legacy hypervisor */
 		prom_debug("Assuming legacy hash support\n");
 	}
+
+	if (supported.xive) {
+		prom_debug("Asking for XIVE\n");
+		ibm_architecture_vec.vec5.intarch = OV5_FEAT(OV5_XIVE_EXPLOIT);
+	}
 }
 
 static void __init prom_send_capabilities(void)