As supported by the printk() (deliberately made visible in context by
also correcting a mis-indented return statement), "above 4GiB" is meant
here. Avoid comparison with a constant to "escape" Misra rule 7.2
complaints. (Note however that even up-to-date Linux, which is where we
"inherited" this code from, still uses the very same off-by-1 check.)

Fixes: 94ea0622c5b8 ("x86-64/mmcfg: relax base address restriction")
Signed-off-by: Jan Beulich <jbeulich@suse.com>

--- a/xen/arch/x86/x86_64/acpi_mmcfg.c
+++ b/xen/arch/x86/x86_64/acpi_mmcfg.c
@@ -50,7 +50,7 @@ static int __init acpi_mcfg_check_entry(
 {
     int year;
 
-    if (cfg->address < 0xFFFFFFFF)
+    if (cfg->address == (uint32_t)cfg->address)
         return 0;
 
     if (!strncmp(mcfg->header.oem_id, "SGI", 3))
@@ -59,7 +59,7 @@ static int __init acpi_mcfg_check_entry(
     if (mcfg->header.revision >= 1 &&
         dmi_get_date(DMI_BIOS_DATE, &year, NULL, NULL) &&
         year >= 2010)
-            return 0;
+        return 0;
 
     printk(KERN_ERR "MCFG region for %04x:%02x-%02x at %#"PRIx64
                     " (above 4GB) ignored\n",

On Mon, Jul 17, 2023 at 11:43:28AM +0200, Jan Beulich wrote:
> As supported by the printk() (deliberately made visible in context by
> also correcting a mis-indented return statement), "above 4GiB" is meant
> here. Avoid comparison with a constant to "escape" Misra rule 7.2
> complaints. (Note however that even up-to-date Linux, which is where we
> "inherited" this code from, still uses the very same off-by-1 check.)
> 
> Fixes: 94ea0622c5b8 ("x86-64/mmcfg: relax base address restriction")
> Signed-off-by: Jan Beulich <jbeulich@suse.com>

Acked-by: Roger Pau Monné <roger.pau@citrix.com>

Albeit I wonder how relevant those checks are anymore, TBH I would be
quite tempted to just drop all this.

Thanks, Roger.