While reviewing a RISC-V patch cloning the Arm code, I noticed an
off-by-1 here: FIX_PMAP_{BEGIN,END} being an inclusive range, FIX_LAST
cannot be the same as FIX_PMAP_END, or else the BUG_ON() in
virt_to_fix() would trigger if FIX_PMAP_END ended up being used.
Fixes: 4f17357b52f6 ("xen/arm: add Persistent Map (PMAP) infrastructure")
Signed-off-by: Jan Beulich <jbeul...@suse.com>
---
Alternatively the definition of FIXADDR_TOP could be changed, if "last"
should retain its strict meaning. Possibly a guard page also wants
having at the end of the fixmap range, which could be effected by
changing both #define-s at the same time.
--- a/xen/arch/arm/include/asm/fixmap.h
+++ b/xen/arch/arm/include/asm/fixmap.h
@@ -15,7 +15,7 @@
#define FIX_PMAP_BEGIN (FIX_ACPI_END + 1) /* Start of PMAP */
#define FIX_PMAP_END (FIX_PMAP_BEGIN + NUM_FIX_PMAP - 1) /* End of PMAP */
-#define FIX_LAST FIX_PMAP_END
+#define FIX_LAST (FIX_PMAP_END + 1)
#define FIXADDR_START FIXMAP_ADDR(0)
#define FIXADDR_TOP FIXMAP_ADDR(FIX_LAST)
