linux-kernel - [PATCH] Re: kvm: unable to handle kernel NULL pointer dereference

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Message-ID: <20080629182828.GA2575@yamamaya.is-a-geek.org>
Date:	Sun, 29 Jun 2008 20:28:28 +0200
From:	Tobias Diedrich <ranma+kernel@...edrich.de>
To:	Chris Wright <chrisw@...s-sol.org>, Avi Kivity <avi@...ranet.com>,
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
	"Roedel, Joerg" <Joerg.Roedel@....com>
Subject: [PATCH] Re: kvm: unable to handle kernel NULL pointer dereference

Tobias Diedrich wrote:
> Chris Wright wrote:
> > * Tobias Diedrich (ranma+kernel@...edrich.de) wrote:
> > > PM: Creating hibernation image: 
> > > PM: Need to copy 126181 pages
> > > PM: Normal pages needed: 126181 + 1024 + 38, available pages: 397721
> > > x86 PAT enabled: cpu 0, old 0x7040600070406, new 0x7010600070106
> > > svm_cpu_init: svm_data is NULL on 0
> > 
> > Yeah, this is broken.  What happens is:
> > 
> > suspend:
> >   hardware_disable
> >     svm_hardware_disable
> >       kfree(svm_data)
> >       per_cpu(svm_data) = NULL
> > 
> > resume:
> >   hardware_enable
> >     svm_hardware_enable
> >       if(!svm_data) printk("svm_cpu_init: svm_data is NULL on 0")
> > 
> > at this point it is broken.
> > 
> > Same would happen on an SMP box by simply doing offline/online of a CPU.
> > This is definitely busted, looking into a patch.
> 
> Any progress on this?

FWIW, it's still broken on 2.6.26-rc8, but the following patch works
for me (tm):

Index: linux-2.6.26-rc8.forcedwol/arch/x86/kvm/svm.c
===================================================================
--- linux-2.6.26-rc8.forcedwol.orig/arch/x86/kvm/svm.c	2008-06-29 20:04:20.000000000 +0200
+++ linux-2.6.26-rc8.forcedwol/arch/x86/kvm/svm.c	2008-06-29 20:12:15.000000000 +0200
@@ -268,6 +268,30 @@
 	return 1;
 }
 
+static int svm_cpu_init(int cpu)
+{
+	struct svm_cpu_data *svm_data;
+	int r;
+
+	svm_data = kzalloc(sizeof(struct svm_cpu_data), GFP_KERNEL);
+	if (!svm_data)
+		return -ENOMEM;
+	svm_data->cpu = cpu;
+	svm_data->save_area = alloc_page(GFP_KERNEL);
+	r = -ENOMEM;
+	if (!svm_data->save_area)
+		goto err_1;
+
+	per_cpu(svm_data, cpu) = svm_data;
+
+	return 0;
+
+err_1:
+	kfree(svm_data);
+	return r;
+
+}
+
 static void svm_hardware_disable(void *garbage)
 {
 	struct svm_cpu_data *svm_data
@@ -293,11 +317,17 @@
 	struct desc_ptr gdt_descr;
 	struct desc_struct *gdt;
 	int me = raw_smp_processor_id();
+	int ret;
 
 	if (!has_svm()) {
-		printk(KERN_ERR "svm_cpu_init: err EOPNOTSUPP on %d\n", me);
+		printk(KERN_ERR "svm_hardware_enable: err EOPNOTSUPP on %d\n", me);
+		return;
+	}
+	if ((ret = svm_cpu_init(me)) != 0) {
+		printk(KERN_ERR "svm_hardware_enable: svm_cpu_init failed on %d with status: %d\n", me, ret);
 		return;
 	}
+
 	svm_data = per_cpu(svm_data, me);
 
 	if (!svm_data) {
@@ -321,30 +351,6 @@
 	       page_to_pfn(svm_data->save_area) << PAGE_SHIFT);
 }
 
-static int svm_cpu_init(int cpu)
-{
-	struct svm_cpu_data *svm_data;
-	int r;
-
-	svm_data = kzalloc(sizeof(struct svm_cpu_data), GFP_KERNEL);
-	if (!svm_data)
-		return -ENOMEM;
-	svm_data->cpu = cpu;
-	svm_data->save_area = alloc_page(GFP_KERNEL);
-	r = -ENOMEM;
-	if (!svm_data->save_area)
-		goto err_1;
-
-	per_cpu(svm_data, cpu) = svm_data;
-
-	return 0;
-
-err_1:
-	kfree(svm_data);
-	return r;
-
-}
-
 static void set_msr_interception(u32 *msrpm, unsigned msr,
 				 int read, int write)
 {

-- 
Tobias						PGP: http://9ac7e0bc.uguu.de
このメールは十割再利用されたビットで作られています。
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