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From:   Boris Ostrovsky <boris.ostrovsky@oracle.com>
To:     tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com
Cc:     x86@kernel.org, linux-kernel@vger.kernel.org,
        xen-devel@lists.xenproject.org, jgross@suse.com,
        andy@strugglers.net, Boris Ostrovsky <boris.ostrovsky@oracle.com>
Subject: [PATCH] x86/EISA: Don't probe EISA bus for Xen PV guests
Date:   Tue, 11 Sep 2018 15:55:38 -0400
Message-Id: <20180911195538.23289-1-boris.ostrovsky@oracle.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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>
---
 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