xen/arm: traps: drop unreachable stage 2 decoding from panic_PAR()

panic_PAR() is only called from va_to_par(), which translates using
__va_to_par(), i.e. "at s1e2r" on arm64 and ATS1HR on arm32. Both
perform an EL2 stage 1 only translation, so PAR.S (PAR_STAGE2) and
PAR.PTW (PAR_STAGE21) can never be set.

This has been the case since commit a14447dbcf ("xen: arm: do not
panic when failing to translate a guest address"), which made
gva_to_par() and gva_to_ipa() return -EFAULT instead of calling
panic_PAR() for guest translations.

Print stage 1 unconditionally and keep an ASSERT() to document the
invariant. PAR_STAGE21 has no user left, so drop it. While at it, fix
the spacing in the decode_fsc() call.

No functional change intended.

Signed-off-by: Michal Orzel <michal.orzel@amd.com>
Reviewed-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>

xen/arch/arm/include/asm/processor.h

@@ -507,7 +507,6 @@ extern register_t __cpu_logical_map[];
 /* .... If F == 1 */
 #define PAR_FSC_SHIFT   (1)
 #define PAR_FSC_MASK    (_AC(0x3f,U)<<PAR_FSC_SHIFT)
-#define PAR_STAGE21     (_AC(1,U)<<8)     /* Stage 2 Fault During Stage 1 Walk */
 #define PAR_STAGE2      (_AC(1,U)<<9)     /* Stage 2 Fault */
 
 /* If F == 0 */

xen/arch/arm/traps.c

@@ -379,16 +379,17 @@ void panic_PAR(uint64_t par)
 {
     const char *msg;
     int level = -1;
-    int stage = par & PAR_STAGE2 ? 2 : 1;
-    int second_in_first = !!(par & PAR_STAGE21);
 
-    msg = decode_fsc( (par&PAR_FSC_MASK) >> PAR_FSC_SHIFT, &level);
+    /*
+     * The only caller translates using "at s1e2r" (arm64) or ATS1HR
+     * (arm32), i.e. an EL2 stage 1 only translation.
+     */
+    ASSERT(!(par & PAR_STAGE2));
 
-    printk("PAR: %016"PRIx64": %s stage %d%s%s\n",
-           par, msg,
-           stage,
-           second_in_first ? " during second stage lookup" : "",
-           fsc_level_str(level));
+    msg = decode_fsc((par & PAR_FSC_MASK) >> PAR_FSC_SHIFT, &level);
+
+    printk("PAR: %016"PRIx64": %s stage 1%s\n",
+           par, msg, fsc_level_str(level));
 
     panic("Error during Hypervisor-to-physical address translation\n");
 }