[Xen-devel] [PATCH] x86/EISA: Don't probe EISA bus for Xen PV guests

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

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@xxxxxxxxxxxxxx>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
---
 arch/x86/kernel/eisa.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/eisa.c b/arch/x86/kernel/eisa.c
index f260e452e4f8..fcf3de1712c8 100644
--- 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;
-- 
2.17.1


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