2 files changed, 34 insertions, 21 deletions

diff --git a/virt/kvm/arm/vgic/vgic-mmio.c b/virt/kvm/arm/vgic/vgic-mmio.c
index e18b30ddcdce..ebe1b9fa3c4d 100644
--- a/virt/kvm/arm/vgic/vgic-mmio.c
+++ b/virt/kvm/arm/vgic/vgic-mmio.c
@@ -453,17 +453,33 @@ 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,
+static bool check_region(const struct kvm *kvm,
+			 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;
+	int flags, nr_irqs = kvm->arch.vgic.nr_spis + VGIC_NR_PRIVATE_IRQS;
+
+	switch (len) {
+	case sizeof(u8):
+		flags = VGIC_ACCESS_8bit;
+		break;
+	case sizeof(u32):
+		flags = VGIC_ACCESS_32bit;
+		break;
+	case sizeof(u64):
+		flags = VGIC_ACCESS_64bit;
+		break;
+	default:
+		return false;
+	}
+
+	if ((region->access_flags & flags) && IS_ALIGNED(addr, len)) {
+		if (!region->bits_per_irq)
+			return true;
+
+		/* Do we access a non-allocated IRQ? */
+		return VGIC_ADDR_TO_INTID(addr, region->bits_per_irq) < nr_irqs;
+	}
 
 	return false;
 }
@@ -477,7 +493,7 @@ static int dispatch_mmio_read(struct kvm_vcpu *vcpu, struct kvm_io_device *dev,
 
 	region = vgic_find_mmio_region(iodev->regions, iodev->nr_regions,
 				       addr - iodev->base_addr);
-	if (!region || !check_region(region, addr, len)) {
+	if (!region || !check_region(vcpu->kvm, region, addr, len)) {
 		memset(val, 0, len);
 		return 0;
 	}
@@ -510,10 +526,7 @@ static int dispatch_mmio_write(struct kvm_vcpu *vcpu, struct kvm_io_device *dev,
 
 	region = vgic_find_mmio_region(iodev->regions, iodev->nr_regions,
 				       addr - iodev->base_addr);
-	if (!region)
-		return 0;
-
-	if (!check_region(region, addr, len))
+	if (!region || !check_region(vcpu->kvm, region, addr, len))
 		return 0;
 
 	switch (iodev->iodev_type) {
diff --git a/virt/kvm/arm/vgic/vgic-mmio.h b/virt/kvm/arm/vgic/vgic-mmio.h
index 4c34d39d44a0..84961b4e4422 100644
--- a/virt/kvm/arm/vgic/vgic-mmio.h
+++ b/virt/kvm/arm/vgic/vgic-mmio.h
@@ -50,15 +50,15 @@ extern struct kvm_io_device_ops kvm_io_gic_ops;
 #define VGIC_ADDR_IRQ_MASK(bits) (((bits) * 1024 / 8) - 1)
 
 /*
- * (addr & mask) gives us the byte offset for the INT ID, so we want to
- * divide this with 'bytes per irq' to get the INT ID, which is given
- * by '(bits) / 8'.  But we do this with fixed-point-arithmetic and
- * take advantage of the fact that division by a fraction equals
- * multiplication with the inverted fraction, and scale up both the
- * numerator and denominator with 8 to support at most 64 bits per IRQ:
+ * (addr & mask) gives us the _byte_ offset for the INT ID.
+ * We multiply this by 8 the get the _bit_ offset, then divide this by
+ * the number of bits to learn the actual INT ID.
+ * But instead of a division (which requires a "long long div" implementation),
+ * we shift by the binary logarithm of <bits>.
+ * This assumes that <bits> is a power of two.
  */
 #define VGIC_ADDR_TO_INTID(addr, bits)  (((addr) & VGIC_ADDR_IRQ_MASK(bits)) * \
-					64 / (bits) / 8)
+					8 >> ilog2(bits))
 
 /*
  * Some VGIC registers store per-IRQ information, with a different number