drivers/xen/xenbus: remove quirk for Xen 3.x

The kernel is not supported to run as a Xen guest on Xen versions
older than 4.0.

Remove xen_strict_xenbus_quirk() which is testing the Xen version to be
at least 4.0.

Acked-by: Stefano Stabellini <sstabellini@kernel.org>
Reviewed-by: Jason Andryuk <jason.andryuk@amd.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Message-ID: <20250815074052.13792-1-jgross@suse.com>

Author: jgross1

drivers/xen/xenbus/xenbus_xs.c

@@ -718,36 +718,13 @@ int xs_watch_msg(struct xs_watch_event *event)
 	return 0;
 }
 
-/*
- * Certain older XenBus toolstack cannot handle reading values that are
- * not populated. Some Xen 3.4 installation are incapable of doing this
- * so if we are running on anything older than 4 do not attempt to read
- * control/platform-feature-xs_reset_watches.
- */
-static bool xen_strict_xenbus_quirk(void)
-{
-#ifdef CONFIG_X86
-	uint32_t eax, ebx, ecx, edx, base;
-
-	base = xen_cpuid_base();
-	cpuid(base + 1, &eax, &ebx, &ecx, &edx);
-
-	if ((eax >> 16) < 4)
-		return true;
-#endif
-	return false;
-
-}
 static void xs_reset_watches(void)
 {
 	int err;
 
 	if (!xen_hvm_domain() || xen_initial_domain())
 		return;
 
-	if (xen_strict_xenbus_quirk())
-		return;
-
 	if (!xenbus_read_unsigned("control",
 				  "platform-feature-xs_reset_watches", 0))
 		return;