linux-kernel - Re: [Bisected][-next-20130204+] [x86/kvm] udevd:[97]: segfault at ffffffffff5fd020 ip 00007fff069e277f sp 00007fff068c9ef8 error d

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Message-ID: <1361741024.21499.37.camel@thor.lan>
Date:	Sun, 24 Feb 2013 16:23:44 -0500
From:	Peter Hurley <peter@...leysoftware.com>
To:	Gleb Natapov <gleb@...hat.com>
Cc:	Marcelo Tosatti <mtosatti@...hat.com>,
	"H. Peter Anvin" <hpa@...ux.intel.com>,
	linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [Bisected][-next-20130204+] [x86/kvm] udevd:[97]: segfault at
 ffffffffff5fd020 ip 00007fff069e277f sp 00007fff068c9ef8 error d

On Tue, 2013-02-19 at 10:26 +0200, Gleb Natapov wrote:
> On Mon, Feb 18, 2013 at 08:12:21PM -0500, Peter Hurley wrote:
> > On Mon, 2013-02-18 at 19:59 -0300, Marcelo Tosatti wrote:
> > > On Wed, Feb 13, 2013 at 06:57:09AM -0500, Peter Hurley wrote:
> > > > On Wed, 2013-02-13 at 12:51 +0200, Gleb Natapov wrote:
> > > > > On Tue, Feb 12, 2013 at 04:39:03PM -0800, H. Peter Anvin wrote:
> > > > > > On 02/12/2013 04:26 PM, Peter Hurley wrote:
> > > > > > > With -next-20130204+ in ubuntu 12.10 VM (so the 80x25 VGA
> > > > > > > device/console):
> > > > > > > 
> > > > > > > [    0.666410] udevd[97]: starting version 175
> > > > > > > [    0.674043] udevd[97]: udevd:[97]: segfault at ffffffffff5fd020 ip 00007fff069e277f sp 00007fff068c9ef8 error d
> > > > > > > 
> > > > > > > and boots to an initramfs prompt.
> > > > > > > 
> > > > > > > git bisect (log attached) blames:
> > > > > > > 
> > > > > > > commit 7b5c4a65cc27f017c170b025f8d6d75dabb11c6f
> > > > > > > Merge: 3596f5b 949db15
> > > > > > > Author: H. Peter Anvin <hpa@...ux.intel.com>
> > > > > > > Date:   Fri Jan 25 16:31:21 2013 -0800
> > > > > > > 
> > > > > > >     Merge tag 'v3.8-rc5' into x86/mm
> > > > > > >     
> > > > > > >     The __pa() fixup series that follows touches KVM code that is not
> > > > > > >     present in the existing branch based on v3.7-rc5, so merge in the
> > > > > > >     current upstream from Linus.
> > > > > > >     
> > > > > > >     Signed-off-by: H. Peter Anvin <hpa@...ux.intel.com>
> > > > > > > 
> > > > > > > 
> > > > > > > This only happens with the VGA device/console but that is the default
> > > > > > > configuration for Ubuntu/KVM because it blacklists pretty much every fb
> > > > > > > driver.
> > > > > > > 
> > > > > > 
> > > > > > I am guessing this is another bad use of __pa()... need to look into that.
> > > 
> > > Can't find this commit on kvm.git or linux-2.6.git. Is it reproducible
> > > there?
> > 
> > This is in the linux-next repo (any git tag after 'next-20130204' will
> > reproduce this). It's a pretty large merge commit.
> > 
> > This doesn't happen on 3.8-rc7.
> > 
> > I'll try to repro this on kvm.git sometime this week. Otherwise, we can
> > wait for it to show up in 3.9.
> > 
> Can you also drop 5dfd486c4750c9278c63fa96e6e85bdd2fb58e9d from linux-next and reproduce?

Ok, found and fixed. This will need to go to stable for 3.8 as well.

Regards,
Peter Hurley

--- >% ---
From: Peter Hurley <peter@...leysoftware.com>
Date: Sun, 24 Feb 2013 10:55:09 -0500
Subject: [PATCH] x86/kvm: Fix pvclock vsyscall fixmap

The physical memory fixmapped for the pvclock clock_gettime vsyscall
was allocated, and thus is not a kernel symbol. __pa() is the proper
method to use in this case.

Fixes the crash below when booting a next-20130204+ smp guest on a
3.8-rc5+ KVM host.

[    0.666410] udevd[97]: starting version 175
[    0.674043] udevd[97]: udevd:[97]: segfault at ffffffffff5fd020
     ip 00007fff069e277f sp 00007fff068c9ef8 error d

Signed-off-by: Peter Hurley <peter@...leysoftware.com>
---
 arch/x86/kernel/pvclock.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/pvclock.c b/arch/x86/kernel/pvclock.c
index 85c3959..2cb9470 100644
--- a/arch/x86/kernel/pvclock.c
+++ b/arch/x86/kernel/pvclock.c
@@ -185,7 +185,7 @@ int __init pvclock_init_vsyscall(struct pvclock_vsyscall_time_info *i,
 
 	for (idx = 0; idx <= (PVCLOCK_FIXMAP_END-PVCLOCK_FIXMAP_BEGIN); idx++) {
 		__set_fixmap(PVCLOCK_FIXMAP_BEGIN + idx,
-			     __pa_symbol(i) + (idx*PAGE_SIZE),
+			     __pa(i) + (idx*PAGE_SIZE),
 			     PAGE_KERNEL_VVAR);
 	}
 
-- 
1.8.1.2



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