[PATCH v6 1/6] xen/arm: vgic-v2: Implement correctly ITARGETSR0 - ITARGETSR7 read-only

[Julien Grall <julien.grall@citrix.com>]

Each ITARGETSR register are 4-byte wide and the offset is in byte.

The current implementation is computing the end of the range wrongly
resulting to emulate only ITARGETSR{0,1} read-only. The rest will be
treated as read-write.

As 8 registers should be read-only, the end of the range should be
ITARGETSR + (4 * 8) - 1.

For convenience introduce ITARGETSR7 and ITARGETSR8.

Signed-off-by: Julien Grall <julien.grall@citrix.com>
Reviewed-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>

---
    This would be a good candidate to backport. Without it a guest could
    modify ITARGETSR{0-7} and redirect the interrupt to the wrong vCPU.

    Spotted while testing to boot FreeBSD guest with this series.
    FreeBSD is writing in ITARGETSR{0 - 7} and will therefore crash xen
    due to the valid ASSERT in vgic_store_itargetsr.

    Note that the emulation is not properly emulated the last register
    of each range. I'm planning to fix it in a follow-up series.

    Changes in v6:
        - Add Stefano's reviewed-by

    Changes in v5:
        - Patch added
---
 xen/arch/arm/vgic-v2.c    | 4 ++--
 xen/include/asm-arm/gic.h | 2 ++
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/xen/arch/arm/vgic-v2.c b/xen/arch/arm/vgic-v2.c
index f7d784b..041291c 100644
--- a/xen/arch/arm/vgic-v2.c
+++ b/xen/arch/arm/vgic-v2.c
@@ -338,11 +338,11 @@ static int vgic_v2_distr_mmio_write(struct vcpu *v, mmio_info_t *info,
                v, r, gicd_reg - GICD_ICACTIVER);
         return 0;
 
-    case GICD_ITARGETSR ... GICD_ITARGETSR + 7:
+    case GICD_ITARGETSR ... GICD_ITARGETSR7:
         /* SGI/PPI target is read only */
         goto write_ignore_32;
 
-    case GICD_ITARGETSR + 8 ... GICD_ITARGETSRN:
+    case GICD_ITARGETSR8 ... GICD_ITARGETSRN:
     {
         /* unsigned long needed for find_next_bit */
         unsigned long target;
diff --git a/xen/include/asm-arm/gic.h b/xen/include/asm-arm/gic.h
index 0116481..3064d1c 100644
--- a/xen/include/asm-arm/gic.h
+++ b/xen/include/asm-arm/gic.h
@@ -42,6 +42,8 @@
 #define GICD_IPRIORITYR (0x400)
 #define GICD_IPRIORITYRN (0x7F8)
 #define GICD_ITARGETSR  (0x800)
+#define GICD_ITARGETSR7 (0x81C)
+#define GICD_ITARGETSR8 (0x820)
 #define GICD_ITARGETSRN (0xBF8)
 #define GICD_ICFGR      (0xC00)
 #define GICD_ICFGRN     (0xCFC)
-- 
2.1.4