[PATCH v2 32/36] irqchip/gic-v5: Check if impl is virt capable

[Sascha Bischoff]

Now that there is support for creating a GICv5-based guest with KVM,
check that the hardware itself supports virtualisation, skipping the
setting of struct gic_kvm_info if not.

Note: If native GICv5 virt is not supported, then nor is
FEAT_GCIE_LEGACY, so we are able to skip altogether.

Signed-off-by: Sascha Bischoff <sascha.bischoff at arm.com>
Reviewed-by: Lorenzo Pieralisi <lpieralisi at kernel.org>
---
 drivers/irqchip/irq-gic-v5-irs.c   |  4 ++++
 drivers/irqchip/irq-gic-v5.c       | 10 ++++++++++
 include/linux/irqchip/arm-gic-v5.h |  4 ++++
 3 files changed, 18 insertions(+)

diff --git a/drivers/irqchip/irq-gic-v5-irs.c b/drivers/irqchip/irq-gic-v5-irs.c
index ce2732d649a3e..eebf9f219ac8c 100644
--- a/drivers/irqchip/irq-gic-v5-irs.c
+++ b/drivers/irqchip/irq-gic-v5-irs.c
@@ -744,6 +744,10 @@ static int __init gicv5_irs_init(struct device_node *node)
 	 */
 	if (list_empty(&irs_nodes)) {
 
+		idr = irs_readl_relaxed(irs_data, GICV5_IRS_IDR0);
+		gicv5_global_data.virt_capable =
+			!!FIELD_GET(GICV5_IRS_IDR0_VIRT, idr);
+
 		idr = irs_readl_relaxed(irs_data, GICV5_IRS_IDR1);
 		irs_setup_pri_bits(idr);
 
diff --git a/drivers/irqchip/irq-gic-v5.c b/drivers/irqchip/irq-gic-v5.c
index 41ef286c4d781..3c86bbc057615 100644
--- a/drivers/irqchip/irq-gic-v5.c
+++ b/drivers/irqchip/irq-gic-v5.c
@@ -1064,6 +1064,16 @@ static struct gic_kvm_info gic_v5_kvm_info __initdata;
 
 static void __init gic_of_setup_kvm_info(struct device_node *node)
 {
+	/*
+	 * If we don't have native GICv5 virtualisation support, then
+	 * we also don't have FEAT_GCIE_LEGACY - the architecture
+	 * forbids this combination.
+	 */
+	if (!gicv5_global_data.virt_capable) {
+		pr_info("GIC implementation is not virtualization capable\n");
+		return;
+	}
+
 	gic_v5_kvm_info.type = GIC_V5;
 
 	/* GIC Virtual CPU interface maintenance interrupt */
diff --git a/include/linux/irqchip/arm-gic-v5.h b/include/linux/irqchip/arm-gic-v5.h
index 2ab7ec718aaea..06ebb2a1cfb1d 100644
--- a/include/linux/irqchip/arm-gic-v5.h
+++ b/include/linux/irqchip/arm-gic-v5.h
@@ -45,6 +45,7 @@
 /*
  * IRS registers and tables structures
  */
+#define GICV5_IRS_IDR0			0x0000
 #define GICV5_IRS_IDR1			0x0004
 #define GICV5_IRS_IDR2			0x0008
 #define GICV5_IRS_IDR5			0x0014
@@ -65,6 +66,8 @@
 #define GICV5_IRS_IST_STATUSR		0x0194
 #define GICV5_IRS_MAP_L2_ISTR		0x01c0
 
+#define GICV5_IRS_IDR0_VIRT		BIT(6)
+
 #define GICV5_IRS_IDR1_PRIORITY_BITS	GENMASK(22, 20)
 #define GICV5_IRS_IDR1_IAFFID_BITS	GENMASK(19, 16)
 
@@ -280,6 +283,7 @@ struct gicv5_chip_data {
 	u8			cpuif_pri_bits;
 	u8			cpuif_id_bits;
 	u8			irs_pri_bits;
+	bool			virt_capable;
 	struct {
 		__le64 *l1ist_addr;
 		u32 l2_size;
-- 
2.34.1