[PATCH v6 09/24] KVM: arm64: vgic-its: Introduce migration ABI infrastructure

[eric.auger@redhat.com (Eric Auger)]

We plan to support different migration ABIs, ie. characterizing
the ITS table layout format in guest RAM. For example, a new ABI
will be needed if vLPIs get supported for nested use case.

So let's introduce an array of supported ABIs (at the moment a single
ABI is supported though). The following characteristics are foreseen
to vary with the ABI: size of table entries, save/restore operation,
the way abi settings are applied.

By default the MAX_ABI_REV is applied on its creation. In subsequent
patches we will introduce a way for the userspace to change the ABI
in use.

The entry sizes now are set according to the ABI version and not
hardcoded anymore.

Signed-off-by: Eric Auger <eric.auger@redhat.com>

---
v6 -> v7:
- rename abi into its_table_abi_versions
- kernel doc comments for struct vgic_its_abi
- comment GIC_ENCODE_SZ
- slighly rephrase the commit message

v5: creation and squash KVM: arm64: ITS: Report the ITE size in
    GITS_TYPER
---
 include/kvm/arm_vgic.h             |  3 ++
 include/linux/irqchip/arm-gic-v3.h |  5 +++
 virt/kvm/arm/vgic/vgic-its.c       | 92 ++++++++++++++++++++++++++++++++++++--
 3 files changed, 96 insertions(+), 4 deletions(-)

diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
index c0b3d99..285474a 100644
--- a/include/kvm/arm_vgic.h
+++ b/include/kvm/arm_vgic.h
@@ -162,6 +162,9 @@ struct vgic_its {
 	u32			creadr;
 	u32			cwriter;
 
+	/* migration ABI revision in use */
+	u32			abi_rev;
+
 	/* Protects the device and collection lists */
 	struct mutex		its_lock;
 	struct list_head	device_list;
diff --git a/include/linux/irqchip/arm-gic-v3.h b/include/linux/irqchip/arm-gic-v3.h
index 97cbca1..81ebe43 100644
--- a/include/linux/irqchip/arm-gic-v3.h
+++ b/include/linux/irqchip/arm-gic-v3.h
@@ -132,6 +132,9 @@
 #define GIC_BASER_SHAREABILITY(reg, type)				\
 	(GIC_BASER_##type << reg##_SHAREABILITY_SHIFT)
 
+/* encode a size field of width @w containing @n - 1 units */
+#define GIC_ENCODE_SZ(n, w) (((unsigned long)(n) - 1) & GENMASK_ULL(((w) - 1), 0))
+
 #define GICR_PROPBASER_SHAREABILITY_SHIFT		(10)
 #define GICR_PROPBASER_INNER_CACHEABILITY_SHIFT		(7)
 #define GICR_PROPBASER_OUTER_CACHEABILITY_SHIFT		(56)
@@ -232,6 +235,7 @@
 #define GITS_CTLR_QUIESCENT		(1U << 31)
 
 #define GITS_TYPER_PLPIS		(1UL << 0)
+#define GITS_TYPER_ITT_ENTRY_SIZE_SHIFT	4
 #define GITS_TYPER_IDBITS_SHIFT		8
 #define GITS_TYPER_DEVBITS_SHIFT	13
 #define GITS_TYPER_DEVBITS(r)		((((r) >> GITS_TYPER_DEVBITS_SHIFT) & 0x1f) + 1)
@@ -290,6 +294,7 @@
 #define GITS_BASER_TYPE(r)		(((r) >> GITS_BASER_TYPE_SHIFT) & 7)
 #define GITS_BASER_ENTRY_SIZE_SHIFT		(48)
 #define GITS_BASER_ENTRY_SIZE(r)	((((r) >> GITS_BASER_ENTRY_SIZE_SHIFT) & 0x1f) + 1)
+#define GITS_BASER_ENTRY_SIZE_MASK	GENMASK_ULL(52, 48)
 #define GITS_BASER_SHAREABILITY_SHIFT	(10)
 #define GITS_BASER_InnerShareable					\
 	GIC_BASER_SHAREABILITY(GITS_BASER, InnerShareable)
diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c
index 18588ef..c336cce 100644
--- a/virt/kvm/arm/vgic/vgic-its.c
+++ b/virt/kvm/arm/vgic/vgic-its.c
@@ -33,6 +33,12 @@
 #include "vgic.h"
 #include "vgic-mmio.h"
 
+/* Highest migration ABI revision supported by this code */
+#define MAX_ABI_REV 0
+
+static int vgic_its_set_abi(struct vgic_its *its, int rev);
+static const struct vgic_its_abi *vgic_its_get_abi(struct vgic_its *its);
+
 /*
  * Creates a new (reference to a) struct vgic_irq for a given LPI.
  * If this LPI is already mapped on another ITS, we increase its refcount
@@ -123,6 +129,25 @@ struct its_ite {
 	u32 event_id;
 };
 
+/**
+ * struct vgic_its_abi - ITS abi ops and settings
+ * @cte_esz: collection table entry size
+ * @dte_esz: device table entry size
+ * @ite_esz: interrupt translation table entry size
+ * @save tables: save the ITS tables into guest RAM
+ * @restore_tables: restore the ITS internal structs from
+ * tables stored in guest RAM
+ * @commit: apply the ABI settings to the ITS
+ */
+struct vgic_its_abi {
+	int cte_esz;
+	int dte_esz;
+	int ite_esz;
+	int (*save_tables)(struct vgic_its *its);
+	int (*restore_tables)(struct vgic_its *its);
+	int (*commit)(struct vgic_its *its);
+};
+
 /*
  * Find and returns a device in the device table for an ITS.
  * Must be called with the its_lock mutex held.
@@ -364,6 +389,7 @@ static unsigned long vgic_mmio_read_its_typer(struct kvm *kvm,
 					      struct vgic_its *its,
 					      gpa_t addr, unsigned int len)
 {
+	const struct vgic_its_abi *abi = vgic_its_get_abi(its);
 	u64 reg = GITS_TYPER_PLPIS;
 
 	/*
@@ -376,6 +402,7 @@ static unsigned long vgic_mmio_read_its_typer(struct kvm *kvm,
 	 */
 	reg |= 0x0f << GITS_TYPER_DEVBITS_SHIFT;
 	reg |= 0x0f << GITS_TYPER_IDBITS_SHIFT;
+	reg |= GIC_ENCODE_SZ(abi->ite_esz, 4) << GITS_TYPER_ITT_ENTRY_SIZE_SHIFT;
 
 	return extract_bytes(reg, addr & 7, len);
 }
@@ -1269,6 +1296,7 @@ static void vgic_mmio_write_its_baser(struct kvm *kvm,
 				      gpa_t addr, unsigned int len,
 				      unsigned long val)
 {
+	const struct vgic_its_abi *abi = vgic_its_get_abi(its);
 	u64 entry_size, device_type;
 	u64 reg, *regptr, clearbits = 0;
 
@@ -1279,12 +1307,12 @@ static void vgic_mmio_write_its_baser(struct kvm *kvm,
 	switch (BASER_INDEX(addr)) {
 	case 0:
 		regptr = &its->baser_device_table;
-		entry_size = 8;
+		entry_size = abi->dte_esz;
 		device_type = GITS_BASER_TYPE_DEVICE;
 		break;
 	case 1:
 		regptr = &its->baser_coll_table;
-		entry_size = 8;
+		entry_size = abi->cte_esz;
 		device_type = GITS_BASER_TYPE_COLLECTION;
 		clearbits = GITS_BASER_INDIRECT;
 		break;
@@ -1426,7 +1454,6 @@ static int vgic_register_its_iodev(struct kvm *kvm, struct vgic_its *its)
 	(GIC_BASER_CACHEABILITY(GITS_BASER, INNER, RaWb)		| \
 	 GIC_BASER_CACHEABILITY(GITS_BASER, OUTER, SameAsInner)		| \
 	 GIC_BASER_SHAREABILITY(GITS_BASER, InnerShareable)		| \
-	 ((8ULL - 1) << GITS_BASER_ENTRY_SIZE_SHIFT)			| \
 	 GITS_BASER_PAGE_SIZE_64K)
 
 #define INITIAL_PROPBASER_VALUE						  \
@@ -1466,7 +1493,7 @@ static int vgic_its_create(struct kvm_device *dev, u32 type)
 
 	dev->private = its;
 
-	return 0;
+	return vgic_its_set_abi(its, MAX_ABI_REV);
 }
 
 static void vgic_its_destroy(struct kvm_device *kvm_dev)
@@ -1584,6 +1611,63 @@ int vgic_its_attr_regs_access(struct kvm_device *dev,
 	return ret;
 }
 
+/**
+ * vgic_its_save_tables_v0 - Save the ITS tables into guest ARM
+ * according to v0 ABI
+ */
+static int vgic_its_save_tables_v0(struct vgic_its *its)
+{
+	return -ENXIO;
+}
+
+/**
+ * vgic_its_restore_tables_v0 - Restore the ITS tables from guest RAM
+ * to internal data structs according to V0 ABI
+ *
+ */
+static int vgic_its_restore_tables_v0(struct vgic_its *its)
+{
+	return -ENXIO;
+}
+
+static int vgic_its_commit_v0(struct vgic_its *its)
+{
+	const struct vgic_its_abi *abi;
+
+	abi = vgic_its_get_abi(its);
+	its->baser_coll_table &= ~GITS_BASER_ENTRY_SIZE_MASK;
+	its->baser_device_table &= ~GITS_BASER_ENTRY_SIZE_MASK;
+
+	its->baser_coll_table |= (GIC_ENCODE_SZ(abi->cte_esz, 5)
+					<< GITS_BASER_ENTRY_SIZE_SHIFT);
+
+	its->baser_device_table |= (GIC_ENCODE_SZ(abi->dte_esz, 5)
+					<< GITS_BASER_ENTRY_SIZE_SHIFT);
+	return 0;
+}
+
+static const struct vgic_its_abi its_table_abi_versions[MAX_ABI_REV + 1] = {
+	{.cte_esz = 8, .dte_esz = 8, .ite_esz = 8,
+	 .save_tables = vgic_its_save_tables_v0,
+	 .restore_tables = vgic_its_restore_tables_v0,
+	 .commit = vgic_its_commit_v0,
+	},
+};
+
+inline const struct vgic_its_abi *vgic_its_get_abi(struct vgic_its *its)
+{
+	return &its_table_abi_versions[its->abi_rev];
+}
+
+int vgic_its_set_abi(struct vgic_its *its, int rev)
+{
+	const struct vgic_its_abi *abi;
+
+	its->abi_rev = rev;
+	abi = vgic_its_get_abi(its);
+	return abi->commit(its);
+}
+
 static int vgic_its_has_attr(struct kvm_device *dev,
 			     struct kvm_device_attr *attr)
 {
-- 
2.5.5