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From:   Ben Hutchings <ben@decadent.org.uk>
To:     linux-kernel@vger.kernel.org, stable@vger.kernel.org
CC:     akpm@linux-foundation.org, xen-devel@lists.xenproject.org,
        "Thomas Gleixner" <tglx@linutronix.de>, jgross@suse.com,
        hpa@zytor.com, "Boris Ostrovsky" <boris.ostrovsky@oracle.com>,
        "Andy Smith" <andy@strugglers.net>
Date:   Sun, 09 Dec 2018 21:50:33 +0000
Message-ID: <lsq.1544392233.175880549@decadent.org.uk>
Subject: [PATCH 3.16 233/328] x86/EISA: Don't probe EISA bus for Xen PV guests
In-Reply-To: <lsq.1544392232.713909046@decadent.org.uk>
Sender: linux-kernel-owner@vger.kernel.org
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3.16.62-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Boris Ostrovsky <boris.ostrovsky@oracle.com>

commit 6a92b11169a65b3f8cc512c75a252cbd0d096ba0 upstream.

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
Link: https://lkml.kernel.org/r/20180911195538.23289-1-boris.ostrovsky@oracle.com
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 arch/x86/kernel/eisa.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

--- a/arch/x86/kernel/eisa.c
+++ b/arch/x86/kernel/eisa.c
@@ -6,11 +6,17 @@
 #include <linux/ioport.h>
 #include <linux/eisa.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;