x86/EISA: Don't probe EISA bus for Xen PV guests

Boris Ostrovsky · KAGA-KOKO · commit 6a92b11169a6 · 2018-09-11T23:36:50.000+02:00
For unprivileged Xen PV guests this is normal memory and ioremap will not be able to properly map it. While at it, since ioremap may return NULL, add a test for pointer's validity. Reported-by: Andy Smith <andy@strugglers.net> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: hpa@zytor.com Cc: xen-devel@lists.xenproject.org Cc: jgross@suse.com Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20180911195538.23289-1-boris.ostrovsky@oracle.com
diff --git a/arch/x86/kernel/eisa.c b/arch/x86/kernel/eisa.c
@@ -7,11 +7,17 @@
 #include <linux/eisa.h>
 #include <linux/io.h>
 
+#include <xen/xen.h>
+
 static __init int eisa_bus_probe(void)
 {
-	void __iomem *p = ioremap(0x0FFFD9, 4);
+	void __iomem *p;
+
+	if (xen_pv_domain() && !xen_initial_domain())
+		return 0;
 
-	if (readl(p) == 'E' + ('I'<<8) + ('S'<<16) + ('A'<<24))
+	p = ioremap(0x0FFFD9, 4);
+	if (p && readl(p) == 'E' + ('I' << 8) + ('S' << 16) + ('A' << 24))
 		EISA_bus = 1;
 	iounmap(p);
 	return 0;
