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

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Date:   Tue, 11 Sep 2018 15:55:38 -0400
From:   Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:     tglx@...utronix.de, mingo@...hat.com, hpa@...or.com
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        xen-devel@...ts.xenproject.org, jgross@...e.com,
        andy@...ugglers.net, Boris Ostrovsky <boris.ostrovsky@...cle.com>
Subject: [PATCH] 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@...ugglers.net>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@...cle.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