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

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
index f260e452e4f8726237618efe4b9526938d31d81d..e8c8c5d78dbdd38b1089f5dc87cf3450644fe487 100644 (file)
--- 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;