Re: [Qemu-devel] TCG assertion with qemu-system-mipsel

["Aurélien Jarno" <aurelien@aurel32.net>]

On Mon, Mar 04, 2013 at 05:37:31PM +0100, Aurélien Jarno wrote:
> Hi,
> 
> On Sat, Feb 23, 2013 at 11:10:18PM +0100, Stefan Weil wrote:
> > This assertion occured with latest git master:
> > 
> > qemu-system-mipsel: /src/qemu/tcg/tcg-op.h:2589:
> >  tcg_gen_goto_tb: Assertion `(tcg_ctx.goto_tb_issue_mask & (1 << idx))
> > == 0' failed.
> > Aborted
> > 
> > QEMU was built with --enable-debug and running a Debian MIPS Lenny (NFS
> > root).
> > The assertion happened when running "apt-get update" in the guest.
> > 
> 
> Is it something reproductible or more or less random? Have you Cc:ed
> Richard because it's related to the latest patches?
> 
> On my side I am experiencing random segfaults in various guests (at
> least PowerPC, MIPS, SH4 and ARM). I have found a way to bisect it, even
> if it is quite long (building Perl + the testsuite). Currently I know
> that 1.3 is affected, while 1.2 is not.
> 

I have found that the issue comes from the following commits, which
unfortunately are not bisectable one by one (though it won't change the
results a lot):

    commit b76f0d8c2e3eac94bc7fd90a510cb7426b2a2699
    Author: Yeongkyoon Lee <yeongkyoon.lee@samsung.com>
    Date:   Wed Oct 31 16:04:25 2012 +0900
    
        tcg: Optimize qemu_ld/st by generating slow paths at the end of a block
        
        Add optimized TCG qemu_ld/st generation which locates the code of TLB miss
        cases at the end of a block after generating the other IRs.
        Currently, this optimization supports only i386 and x86_64 hosts.
        
        Signed-off-by: Yeongkyoon Lee <yeongkyoon.lee@samsung.com>
        Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
    
    commit fdbb84d1332ae0827d60f1a2ca03c7d5678c6edd
    Author: Yeongkyoon Lee <yeongkyoon.lee@samsung.com>
    Date:   Wed Oct 31 16:04:24 2012 +0900
    
        tcg: Add extended GETPC mechanism for MMU helpers with ldst optimization
        
        Add GETPC_EXT which is used by MMU helpers to selectively calculate the code
        address of accessing guest memory when called from a qemu_ld/st optimized code
        or a C function. Currently, it supports only i386 and x86-64 hosts.
        
        Signed-off-by: Yeongkyoon Lee <yeongkyoon.lee@samsung.com>
        Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
    
    commit 32761257c0b9fa7ee04d2871a6e48a41f119c469
    Author: Yeongkyoon Lee <yeongkyoon.lee@samsung.com>
    Date:   Wed Oct 31 16:04:23 2012 +0900
    
        configure: Add CONFIG_QEMU_LDST_OPTIMIZATION for TCG qemu_ld/st optimization
        
        Enable CONFIG_QEMU_LDST_OPTIMIZATION for TCG qemu_ld/st optimization only when
        a host is i386 or x86_64.
        
        Signed-off-by: Yeongkyoon Lee <yeongkyoon.lee@samsung.com>
        Signed-off-by: Blue Swirl <blauwirbel@gmail.com>

I will try to understand why.


-- 
Aurelien Jarno                          GPG: 1024D/F1BCDB73
aurelien@aurel32.net                 http://www.aurel32.net