KVM: arm64: vgic-its: Implement basic ITS register handlers

Add emulation for some basic MMIO registers used in the ITS emulation.
This includes:
- GITS_{CTLR,TYPER,IIDR}
- ID registers
- GITS_{CBASER,CREADR,CWRITER}
  (which implement the ITS command buffer handling)
- GITS_BASER<n>

Most of the handlers are pretty straight forward, only the CWRITER
handler is a bit more involved by taking the new its_cmd mutex and
then iterating over the command buffer.
The registers holding base addresses and attributes are sanitised before
storing them.
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Tested-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

include/kvm/arm_vgic.h

@@ -22,6 +22,7 @@
 #include <linux/spinlock.h>
 #include <linux/types.h>
 #include <kvm/iodev.h>
+#include <linux/list.h>
 
 #define VGIC_V3_MAX_CPUS	255
 #define VGIC_V2_MAX_CPUS	8
@@ -136,6 +137,21 @@ struct vgic_its {
 	bool			enabled;
 	bool			initialized;
 	struct vgic_io_device	iodev;
+
+	/* These registers correspond to GITS_BASER{0,1} */
+	u64			baser_device_table;
+	u64			baser_coll_table;
+
+	/* Protects the command queue */
+	struct mutex		cmd_lock;
+	u64			cbaser;
+	u32			creadr;
+	u32			cwriter;
+
+	/* Protects the device and collection lists */
+	struct mutex		its_lock;
+	struct list_head	device_list;
+	struct list_head	collection_list;
 };
 
 struct vgic_dist {

virt/kvm/arm/vgic/vgic-mmio-v3.c

@@ -23,15 +23,15 @@
 #include "vgic-mmio.h"
 
 /* extract @num bytes at @offset bytes offset in data */
-static unsigned long extract_bytes(unsigned long data, unsigned int offset,
-				   unsigned int num)
+unsigned long extract_bytes(unsigned long data, unsigned int offset,
+			    unsigned int num)
 {
 	return (data >> (offset * 8)) & GENMASK_ULL(num * 8 - 1, 0);
 }
 
 /* allows updates of any half of a 64-bit register (or the whole thing) */
-static u64 update_64bit_reg(u64 reg, unsigned int offset, unsigned int len,
-			    unsigned long val)
+u64 update_64bit_reg(u64 reg, unsigned int offset, unsigned int len,
+		     unsigned long val)
 {
 	int lower = (offset & 4) * 8;
 	int upper = lower + 8 * len - 1;

virt/kvm/arm/vgic/vgic-mmio.h

@@ -96,6 +96,12 @@ unsigned long vgic_data_mmio_bus_to_host(const void *val, unsigned int len);
 void vgic_data_host_to_mmio_bus(void *buf, unsigned int len,
 				unsigned long data);
 
+unsigned long extract_bytes(unsigned long data, unsigned int offset,
+			    unsigned int num);
+
+u64 update_64bit_reg(u64 reg, unsigned int offset, unsigned int len,
+		     unsigned long val);
+
 unsigned long vgic_mmio_read_raz(struct kvm_vcpu *vcpu,
 				 gpa_t addr, unsigned int len);
 

virt/kvm/arm/vgic/vgic.c

@@ -33,10 +33,16 @@ struct vgic_global __section(.hyp.text) kvm_vgic_global_state;
 
 /*
  * Locking order is always:
- *   vgic_cpu->ap_list_lock
- *     vgic_irq->irq_lock
+ * its->cmd_lock (mutex)
+ *   its->its_lock (mutex)
+ *     vgic_cpu->ap_list_lock
+ *       vgic_irq->irq_lock
  *
- * (that is, always take the ap_list_lock before the struct vgic_irq lock).
+ * If you need to take multiple locks, always take the upper lock first,
+ * then the lower ones, e.g. first take the its_lock, then the irq_lock.
+ * If you are already holding a lock and need to take a higher one, you
+ * have to drop the lower ranking lock first and re-aquire it after having
+ * taken the upper one.
  *
  * When taking more than one ap_list_lock at the same time, always take the
  * lowest numbered VCPU's ap_list_lock first, so: