Add GICv2m support

GICv2m is a small extension to the GICv2 architecture, specified in the
Server Base System Architecture (SBSA). It adds a set of register to
converts MSIs into SPIs, effectively enabling MSI support for pre-GICv3
platforms.

Implement a GICv2m emulation entirely in userspace. Add a thin translation
layer in irq.c to catch the MSI->SPI routing setup of the guest, and then
transform irqfd injection of MSI into the associated SPI. There shouldn't
be any significant runtime overhead compared to gicv3-its.

The device can be enabled by passing "--irqchip gicv2m" to kvmtool.

Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

6 files changed, 173 insertions, 1 deletions

diff --git a/arm/aarch32/include/asm/kvm.h b/arm/aarch32/include/asm/kvm.h
index 6ebd3e6a..02206673 100644
--- a/arm/aarch32/include/asm/kvm.h
+++ b/arm/aarch32/include/asm/kvm.h
@@ -84,6 +84,8 @@ struct kvm_regs {
 #define KVM_VGIC_V2_DIST_SIZE		0x1000
 #define KVM_VGIC_V2_CPU_SIZE		0x2000
 
+#define KVM_VGIC_V2M_SIZE		0x1000
+
 /* Supported VGICv3 address types  */
 #define KVM_VGIC_V3_ADDR_TYPE_DIST	2
 #define KVM_VGIC_V3_ADDR_TYPE_REDIST	3
diff --git a/arm/aarch64/include/asm/kvm.h b/arm/aarch64/include/asm/kvm.h
index c2860358..7d14507b 100644
--- a/arm/aarch64/include/asm/kvm.h
+++ b/arm/aarch64/include/asm/kvm.h
@@ -84,6 +84,8 @@ struct kvm_regs {
 #define KVM_VGIC_V2_DIST_SIZE		0x1000
 #define KVM_VGIC_V2_CPU_SIZE		0x2000
 
+#define KVM_VGIC_V2M_SIZE		0x1000
+
 /* Supported VGICv3 address types  */
 #define KVM_VGIC_V3_ADDR_TYPE_DIST	2
 #define KVM_VGIC_V3_ADDR_TYPE_REDIST	3
diff --git a/arm/gic.c b/arm/gic.c
index 9de6a9c9..aca0b939 100644
--- a/arm/gic.c
+++ b/arm/gic.c
@@ -24,6 +24,8 @@ int irqchip_parser(const struct option *opt, const char *arg, int unset)
 
 	if (!strcmp(arg, "gicv2")) {
 		*type = IRQCHIP_GICV2;
+	} else if (!strcmp(arg, "gicv2m")) {
+		*type = IRQCHIP_GICV2M;
 	} else if (!strcmp(arg, "gicv3")) {
 		*type = IRQCHIP_GICV3;
 	} else if (!strcmp(arg, "gicv3-its")) {
@@ -107,6 +109,8 @@ static int gic__create_msi_frame(struct kvm *kvm, enum irqchip_type type,
 				 u64 msi_frame_addr)
 {
 	switch (type) {
+	case IRQCHIP_GICV2M:
+		return gic__create_gicv2m_frame(kvm, msi_frame_addr);
 	case IRQCHIP_GICV3_ITS:
 		return gic__create_its_frame(kvm, msi_frame_addr);
 	default:	/* No MSI frame needed */
@@ -138,6 +142,7 @@ static int gic__create_device(struct kvm *kvm, enum irqchip_type type)
 	};
 
 	switch (type) {
+	case IRQCHIP_GICV2M:
 	case IRQCHIP_GICV2:
 		gic_device.type = KVM_DEV_TYPE_ARM_VGIC_V2;
 		dist_attr.attr  = KVM_VGIC_V2_ADDR_TYPE_DIST;
@@ -156,6 +161,7 @@ static int gic__create_device(struct kvm *kvm, enum irqchip_type type)
 	gic_fd = gic_device.fd;
 
 	switch (type) {
+	case IRQCHIP_GICV2M:
 	case IRQCHIP_GICV2:
 		err = ioctl(gic_fd, KVM_SET_DEVICE_ATTR, &cpu_if_attr);
 		break;
@@ -216,6 +222,10 @@ int gic__create(struct kvm *kvm, enum irqchip_type type)
 	int err;
 
 	switch (type) {
+	case IRQCHIP_GICV2M:
+		gic_msi_size = KVM_VGIC_V2M_SIZE;
+		gic_msi_base = ARM_GIC_DIST_BASE - gic_msi_size;
+		break;
 	case IRQCHIP_GICV2:
 		break;
 	case IRQCHIP_GICV3_ITS:
@@ -296,6 +306,9 @@ void gic__generate_fdt_nodes(void *fdt, enum irqchip_type type)
 	};
 
 	switch (type) {
+	case IRQCHIP_GICV2M:
+		msi_compatible = "arm,gic-v2m-frame";
+		/* fall-through */
 	case IRQCHIP_GICV2:
 		compatible = "arm,cortex-a15-gic";
 		reg_prop[2] = cpu_to_fdt64(ARM_GIC_CPUI_BASE);
diff --git a/arm/gicv2m.c b/arm/gicv2m.c
new file mode 100644
index 00000000..d7e6398a
--- /dev/null
+++ b/arm/gicv2m.c
@@ -0,0 +1,153 @@
+#include <errno.h>
+#include <stdlib.h>
+
+#include "kvm/irq.h"
+#include "kvm/kvm.h"
+#include "kvm/util.h"
+
+#include "arm-common/gic.h"
+
+#define GICV2M_MSI_TYPER	0x008
+#define GICV2M_MSI_SETSPI	0x040
+#define GICV2M_MSI_IIDR		0xfcc
+
+#define GICV2M_SPI_MASK		0x3ff
+#define GICV2M_MSI_TYPER_VAL(start, nr)	\
+	(((start) & GICV2M_SPI_MASK) << 16 | ((nr) & GICV2M_SPI_MASK))
+
+struct gicv2m_chip {
+	int	first_spi;
+	int	num_spis;
+	int	*spis;
+	u64	base;
+	u64	size;
+};
+
+static struct gicv2m_chip v2m;
+
+/*
+ * MSI routing is setup lazily, when the guest writes the MSI tables. The guest
+ * writes which SPI is associated to an MSI vector into the message data field.
+ * The IRQ code notifies us of any change to MSI routing via this callback.
+ * Store the MSI->SPI translation for later.
+ *
+ * Data is the GIC interrupt ID, that includes SGIs and PPIs. SGIs at 0-15, PPIs
+ * are 16-31 and SPIs are 32-1019. What we're saving for later is the MSI's GSI
+ * number, a logical ID used by KVM for routing. The GSI of an SPI is implicitly
+ * defined by KVM to be its pin number (SPI index), and the GSI of an MSI is
+ * allocated by kvmtool.
+ */
+static int gicv2m_update_routing(struct kvm *kvm,
+				 struct kvm_irq_routing_entry *entry)
+{
+	int spi;
+
+	if (entry->type != KVM_IRQ_ROUTING_MSI)
+		return -EINVAL;
+
+	if (!entry->u.msi.address_hi && !entry->u.msi.address_lo)
+		return 0;
+
+	spi = entry->u.msi.data & GICV2M_SPI_MASK;
+	if (spi < v2m.first_spi || spi >= v2m.first_spi + v2m.num_spis) {
+		pr_err("invalid SPI number %d", spi);
+		return -EINVAL;
+	}
+
+	v2m.spis[spi - v2m.first_spi] = entry->gsi;
+
+	return 0;
+}
+
+/*
+ * Find SPI bound to the given MSI and return the associated GSI.
+ */
+static int gicv2m_translate_gsi(struct kvm *kvm, u32 gsi)
+{
+	int i;
+
+	for (i = 0; i < v2m.num_spis; i++) {
+		if (v2m.spis[i] == (int)gsi)
+			return i + v2m.first_spi - KVM_IRQ_OFFSET;
+	}
+
+	/* Not an MSI */
+	return gsi;
+}
+
+static bool gicv2m_can_signal_msi(struct kvm *kvm)
+{
+	return true;
+}
+
+/*
+ * Instead of setting up MSI routes, virtual devices can also trigger them
+ * manually (like a direct write to MSI_SETSPI). In this case, trigger the SPI
+ * directly.
+ */
+static int gicv2m_signal_msi(struct kvm *kvm, struct kvm_msi *msi)
+{
+	int spi = msi->data & GICV2M_SPI_MASK;
+
+	if (spi < v2m.first_spi || spi >= v2m.first_spi + v2m.num_spis) {
+		pr_err("invalid SPI number %d", spi);
+		return -EINVAL;
+	}
+
+	kvm__irq_trigger(kvm, spi);
+	return 0;
+}
+
+static struct msi_routing_ops gicv2m_routing = {
+	.update_route	= gicv2m_update_routing,
+	.translate_gsi	= gicv2m_translate_gsi,
+	.can_signal_msi	= gicv2m_can_signal_msi,
+	.signal_msi	= gicv2m_signal_msi,
+};
+
+static void gicv2m_mmio_callback(struct kvm_cpu *vcpu, u64 addr, u8 *data,
+				  u32 len, u8 is_write, void *ptr)
+{
+	if (is_write)
+		return;
+
+	addr -= v2m.base;
+
+	switch (addr) {
+		case GICV2M_MSI_TYPER:
+			*(u32 *)data = GICV2M_MSI_TYPER_VAL(v2m.first_spi,
+							    v2m.num_spis);
+			break;
+		case GICV2M_MSI_IIDR:
+			*(u32 *)data = 0x0;
+			break;
+	}
+}
+
+int gic__create_gicv2m_frame(struct kvm *kvm, u64 base)
+{
+	int i;
+	int irq = irq__alloc_line();
+
+	v2m = (struct gicv2m_chip) {
+		.first_spi	= irq,	/* Includes GIC_SPI_IRQ_BASE */
+		.num_spis	= 64,	/* arbitrary */
+		.base		= base,
+		.size		= KVM_VGIC_V2M_SIZE,
+	};
+
+	v2m.spis = calloc(v2m.num_spis, sizeof(int));
+	if (!v2m.spis)
+		return -ENOMEM;
+
+	v2m.spis[0] = -1;
+	for (i = 1; i < v2m.num_spis; i++) {
+		irq__alloc_line();
+		v2m.spis[i] = -1;
+	}
+
+	msi_routing_ops = &gicv2m_routing;
+
+	return kvm__register_mmio(kvm, base, KVM_VGIC_V2M_SIZE, false,
+				  gicv2m_mmio_callback, kvm);
+}
diff --git a/arm/include/arm-common/gic.h b/arm/include/arm-common/gic.h
index 433dd237..687effc6 100644
--- a/arm/include/arm-common/gic.h
+++ b/arm/include/arm-common/gic.h
@@ -23,6 +23,7 @@
 
 enum irqchip_type {
 	IRQCHIP_GICV2,
+	IRQCHIP_GICV2M,
 	IRQCHIP_GICV3,
 	IRQCHIP_GICV3_ITS,
 };
@@ -31,6 +32,7 @@ struct kvm;
 
 int gic__alloc_irqnum(void);
 int gic__create(struct kvm *kvm, enum irqchip_type type);
+int gic__create_gicv2m_frame(struct kvm *kvm, u64 msi_frame_addr);
 void gic__generate_fdt_nodes(void *fdt, enum irqchip_type type);
 
 #endif /* ARM_COMMON__GIC_H */
diff --git a/arm/include/arm-common/kvm-config-arch.h b/arm/include/arm-common/kvm-config-arch.h
index f18b2c88..6a196f18 100644
--- a/arm/include/arm-common/kvm-config-arch.h
+++ b/arm/include/arm-common/kvm-config-arch.h
@@ -28,7 +28,7 @@ int irqchip_parser(const struct option *opt, const char *arg, int unset);
 		    "Force virtio devices to use PCI as their default "		\
 		    "transport"),						\
         OPT_CALLBACK('\0', "irqchip", &(cfg)->irqchip,				\
-		     "[gicv2|gicv3|gicv3-its]",					\
+		     "[gicv2|gicv2m|gicv3|gicv3-its]",				\
 		     "Type of interrupt controller to emulate in the guest",	\
 		     irqchip_parser, NULL),