[PATCH 5/5] ARM64: KVM: fix vgic_bitmap_get_reg function for BE 64bit case

[Victor Kamensky]

Fix vgic_bitmap_get_reg function to return 'right' word address of
'unsigned long' bitmap value in case of BE 64bit image.

Signed-off-by: Victor Kamensky <victor.kamensky at linaro.org>
---
 virt/kvm/arm/vgic.c | 27 +++++++++++++++++++++++++--
 1 file changed, 25 insertions(+), 2 deletions(-)

diff --git a/virt/kvm/arm/vgic.c b/virt/kvm/arm/vgic.c
index 7e11458..e56c5f8 100644
--- a/virt/kvm/arm/vgic.c
+++ b/virt/kvm/arm/vgic.c
@@ -96,14 +96,37 @@ static u32 vgic_nr_lr;
 
 static unsigned int vgic_maint_irq;
 
+/*
+ * struct vgic_bitmap is union that provides two view of
+ * the same data. In one case it is array of registers of
+ * u32 type (.reg). And in another it is bitmap, which is
+ * array of 'unsgined long' (.reg_ul). It works all well in
+ * case of 32bit (u32 and 'unsigned long' have the same size).
+ * It works ok in 64bit LE case, where 'unsigned long'
+ * size is 8 bytes, while u32 is 4 bytes, and least siginificant
+ * word of 'unsigned long' matches lower index of .reg array.
+ * It breaks in 64bit BE case. In this case word sized
+ * register of even index actually resides in least significant
+ * word of 'unsigned long' which has address at offset plus 4
+ * bytes. And word sized register of odd index resides at most
+ * significant of 'unsigned long' which has offset minus 4
+ * bytes. Define REG_OFFSET_SWIZZLE that would help to
+ * change offset of register in case of BE 64bit system.
+ */
+#if defined(CONFIG_CPU_BIG_ENDIAN) && BITS_PER_LONG == 64
+#define REG_OFFSET_SWIZZLE	1
+#else
+#define REG_OFFSET_SWIZZLE	0
+#endif
+
 static u32 *vgic_bitmap_get_reg(struct vgic_bitmap *x,
 				int cpuid, u32 offset)
 {
 	offset >>= 2;
 	if (!offset)
-		return x->percpu[cpuid].reg;
+		return x->percpu[cpuid].reg + (offset^REG_OFFSET_SWIZZLE);
 	else
-		return x->shared.reg + offset - 1;
+		return x->shared.reg + ((offset - 1)^REG_OFFSET_SWIZZLE);
 }
 
 static int vgic_bitmap_get_irq_val(struct vgic_bitmap *x,
-- 
1.8.1.4