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

BugLink: https://bugs.launchpad.net/bugs/1789118
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
(cherry picked from commit 6a92b11169a65b3f8cc512c75a252cbd0d096ba0)
Signed-off-by: Joseph Salisbury <joseph.salisbury@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.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;