This is done indirectly by adjusting two typedefs and helps emphasizing
that the respective tables aren't supposed to be modified at runtime
(as they may be shared between devices).

Signed-off-by: Jan Beulich <jbeulich@suse.com>

--- a/qemu/upstream/hw/xen/xen_pt.h
+++ b/qemu/upstream/hw/xen/xen_pt.h
@@ -31,7 +31,7 @@ void xen_pt_log(const PCIDevice *d, cons
 /* Helper */
 #define XEN_PFN(x) ((x) >> XC_PAGE_SHIFT)
 
-typedef struct XenPTRegInfo XenPTRegInfo;
+typedef const struct XenPTRegInfo XenPTRegInfo;
 typedef struct XenPTReg XenPTReg;
 
 typedef struct XenPCIPassthroughState XenPCIPassthroughState;
@@ -135,11 +135,11 @@ struct XenPTReg {
     uint32_t data; /* emulated value */
 };
 
-typedef struct XenPTRegGroupInfo XenPTRegGroupInfo;
+typedef const struct XenPTRegGroupInfo XenPTRegGroupInfo;
 
 /* emul reg group size initialize method */
 typedef int (*xen_pt_reg_size_init_fn)
-    (XenPCIPassthroughState *, const XenPTRegGroupInfo *,
+    (XenPCIPassthroughState *, XenPTRegGroupInfo *,
      uint32_t base_offset, uint8_t *size);
 
 /* emulated register group information */
@@ -154,7 +154,7 @@ struct XenPTRegGroupInfo {
 /* emul register group management table */
 typedef struct XenPTRegGroup {
     QLIST_ENTRY(XenPTRegGroup) entries;
-    const XenPTRegGroupInfo *reg_grp;
+    XenPTRegGroupInfo *reg_grp;
     uint32_t base_offset;
     uint8_t size;
     QLIST_HEAD(, XenPTReg) reg_tbl_list;
--- a/qemu/upstream/hw/xen/xen_pt_config_init.c
+++ b/qemu/upstream/hw/xen/xen_pt_config_init.c
@@ -96,8 +96,7 @@ XenPTReg *xen_pt_find_reg(XenPTRegGroup 
 }
 
 static uint32_t get_throughable_mask(const XenPCIPassthroughState *s,
-                                     const XenPTRegInfo *reg,
-                                     uint32_t valid_mask)
+                                     XenPTRegInfo *reg, uint32_t valid_mask)
 {
     uint32_t throughable_mask = ~(reg->emu_mask | reg->ro_mask);