KVM: arm/arm64: vgic-new: Add MMIO handling framework

Add an MMIO handling framework to the VGIC emulation:
Each register is described by its offset, size (or number of bits per
IRQ, if applicable) and the read/write handler functions. We provide
initialization macros to describe each GIC register later easily.

Separate dispatch functions for read and write accesses are connected
to the kvm_io_bus framework and binary-search for the responsible
register handler based on the offset address within the region.
We convert the incoming data (referenced by a pointer) to the host's
endianess and use pass-by-value to hand the data over to the actual
handler functions.

The register handler prototype and the endianess conversion are
courtesy of Christoffer Dall.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>

1 files changed, 184 insertions, 0 deletions

diff --git a/virt/kvm/arm/vgic/vgic-mmio.c b/virt/kvm/arm/vgic/vgic-mmio.c
new file mode 100644
index 000000000000..012b82bec918
--- /dev/null
+++ b/virt/kvm/arm/vgic/vgic-mmio.c
@@ -0,0 +1,184 @@
+/*
+ * VGIC MMIO handling functions
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/bitops.h>
+#include <linux/bsearch.h>
+#include <linux/kvm.h>
+#include <linux/kvm_host.h>
+#include <kvm/iodev.h>
+#include <kvm/arm_vgic.h>
+
+#include "vgic.h"
+#include "vgic-mmio.h"
+
+unsigned long vgic_mmio_read_raz(struct kvm_vcpu *vcpu,
+				 gpa_t addr, unsigned int len)
+{
+	return 0;
+}
+
+unsigned long vgic_mmio_read_rao(struct kvm_vcpu *vcpu,
+				 gpa_t addr, unsigned int len)
+{
+	return -1UL;
+}
+
+void vgic_mmio_write_wi(struct kvm_vcpu *vcpu, gpa_t addr,
+			unsigned int len, unsigned long val)
+{
+	/* Ignore */
+}
+
+static int match_region(const void *key, const void *elt)
+{
+	const unsigned int offset = (unsigned long)key;
+	const struct vgic_register_region *region = elt;
+
+	if (offset < region->reg_offset)
+		return -1;
+
+	if (offset >= region->reg_offset + region->len)
+		return 1;
+
+	return 0;
+}
+
+/* Find the proper register handler entry given a certain address offset. */
+static const struct vgic_register_region *
+vgic_find_mmio_region(const struct vgic_register_region *region, int nr_regions,
+		      unsigned int offset)
+{
+	return bsearch((void *)(uintptr_t)offset, region, nr_regions,
+		       sizeof(region[0]), match_region);
+}
+
+/*
+ * kvm_mmio_read_buf() returns a value in a format where it can be converted
+ * to a byte array and be directly observed as the guest wanted it to appear
+ * in memory if it had done the store itself, which is LE for the GIC, as the
+ * guest knows the GIC is always LE.
+ *
+ * We convert this value to the CPUs native format to deal with it as a data
+ * value.
+ */
+unsigned long vgic_data_mmio_bus_to_host(const void *val, unsigned int len)
+{
+	unsigned long data = kvm_mmio_read_buf(val, len);
+
+	switch (len) {
+	case 1:
+		return data;
+	case 2:
+		return le16_to_cpu(data);
+	case 4:
+		return le32_to_cpu(data);
+	default:
+		return le64_to_cpu(data);
+	}
+}
+
+/*
+ * kvm_mmio_write_buf() expects a value in a format such that if converted to
+ * a byte array it is observed as the guest would see it if it could perform
+ * the load directly.  Since the GIC is LE, and the guest knows this, the
+ * guest expects a value in little endian format.
+ *
+ * We convert the data value from the CPUs native format to LE so that the
+ * value is returned in the proper format.
+ */
+void vgic_data_host_to_mmio_bus(void *buf, unsigned int len,
+				unsigned long data)
+{
+	switch (len) {
+	case 1:
+		break;
+	case 2:
+		data = cpu_to_le16(data);
+		break;
+	case 4:
+		data = cpu_to_le32(data);
+		break;
+	default:
+		data = cpu_to_le64(data);
+	}
+
+	kvm_mmio_write_buf(buf, len, data);
+}
+
+static
+struct vgic_io_device *kvm_to_vgic_iodev(const struct kvm_io_device *dev)
+{
+	return container_of(dev, struct vgic_io_device, dev);
+}
+
+static bool check_region(const struct vgic_register_region *region,
+			 gpa_t addr, int len)
+{
+	if ((region->access_flags & VGIC_ACCESS_8bit) && len == 1)
+		return true;
+	if ((region->access_flags & VGIC_ACCESS_32bit) &&
+	    len == sizeof(u32) && !(addr & 3))
+		return true;
+	if ((region->access_flags & VGIC_ACCESS_64bit) &&
+	    len == sizeof(u64) && !(addr & 7))
+		return true;
+
+	return false;
+}
+
+static int dispatch_mmio_read(struct kvm_vcpu *vcpu, struct kvm_io_device *dev,
+			      gpa_t addr, int len, void *val)
+{
+	struct vgic_io_device *iodev = kvm_to_vgic_iodev(dev);
+	const struct vgic_register_region *region;
+	struct kvm_vcpu *r_vcpu;
+	unsigned long data;
+
+	region = vgic_find_mmio_region(iodev->regions, iodev->nr_regions,
+				       addr - iodev->base_addr);
+	if (!region || !check_region(region, addr, len)) {
+		memset(val, 0, len);
+		return 0;
+	}
+
+	r_vcpu = iodev->redist_vcpu ? iodev->redist_vcpu : vcpu;
+	data = region->read(r_vcpu, addr, len);
+	vgic_data_host_to_mmio_bus(val, len, data);
+	return 0;
+}
+
+static int dispatch_mmio_write(struct kvm_vcpu *vcpu, struct kvm_io_device *dev,
+			       gpa_t addr, int len, const void *val)
+{
+	struct vgic_io_device *iodev = kvm_to_vgic_iodev(dev);
+	const struct vgic_register_region *region;
+	struct kvm_vcpu *r_vcpu;
+	unsigned long data = vgic_data_mmio_bus_to_host(val, len);
+
+	region = vgic_find_mmio_region(iodev->regions, iodev->nr_regions,
+				       addr - iodev->base_addr);
+	if (!region)
+		return 0;
+
+	if (!check_region(region, addr, len))
+		return 0;
+
+	r_vcpu = iodev->redist_vcpu ? iodev->redist_vcpu : vcpu;
+	region->write(r_vcpu, addr, len, data);
+	return 0;
+}
+
+struct kvm_io_device_ops kvm_io_gic_ops = {
+	.read = dispatch_mmio_read,
+	.write = dispatch_mmio_write,
+};