Re: Re: [Qemu-devel] Bug with TARGET_PHYS_ADDR_SPACE_BITS

[Alan Pevec <apevec@redhat.com>]

Anthony Liguori wrote:
>Chris Lalancette wrote:
>> Hello,
>>      oVirt is currently using straight x86_64 qemu emulation for 
>> certain parts
>> of the architecture (we mostly use KVM, but need to use full emulation 
>> for a
>> couple of parts).  We recently upgraded our userspace package to 
>> kvm-72, but
>> found that we could not PXE boot guests when we were doing full 
>> emulation (under
>> kvm, we could PXE boot just fine).  We also tried using qemu SVN tip, 
>> with
>> similar results.  We ended up doing a bisect, and tracked down the 
>> problem to
>> this commit (from the kvm repo, but pulled from qemu):
>>
>> http://git.kernel.org/?p=linux/kernel/git/amit/kvm-userspace.git;a=commit;h=468f7507339a5236bff8ab339eb0c1b019a95fda 
>>
>>
>> The important changes in there in terms of this bug revolves around
>> TARGET_PHYS_ADDR_SPACE_BITS in exec.c.  If I change that back to 32 
>> (what it was
>> before this patch for x86_64), the PXE boot succeeds.  Also, if I remove
>> TARGET_PHYS_ADDR_SPACE_BITS > 32 conditional code in 
>> phys_page_find_alloc(), but
>> leave TARGET_PHYS_ADDR_SPACE_BITS as 42, the PXE boot also works.  I 
>> can't claim
>> to understand the conditional code I've compiled out, so I'm not sure 
>> where the
>> bug would be.  Does anyone have an idea what the problem might be?
>>   
> 
> Right now, the code just can't handle TARGET_PHYS_ADDR_SPACES_BITS > 
> 32.  This may help you:

I applied that to qemu svn trunk but still get the same tripple fault w/ pxelinux (syslinux-3.61-2.fc9)
qemu: fatal: triple fault
EAX=0f8ef0a8 EBX=f0711ae0 ECX=f07b0244 EDX=f07b026e
ESI=f0711adc EDI=00000001 EBP=0f8ee990 ESP=f07b0016
EIP=00000717 EFL=00000002 [-------] CPL=0 II=0 A20=1 SMM=0 HLT=0
ES =0010 0f8ee990 ffffffff 0fcf938e
CS =0008 0f8ee990 ffffffff 0fcf9f8e
SS =0010 0f8ee990 ffffffff 0fcf938e
DS =0010 0f8ee990 ffffffff 0fcf938e
FS =0010 0f8ee990 ffffffff 0fcf938e
GS =0010 0f8ee990 ffffffff 0fcf938e
LDT=0000 00000000 0000ffff 00008200
TR =0000 00000000 0000ffff 00008b00
GDT=     0f8f6ed0 00000037
IDT=     00000000 000003ff
CR0=00000011 CR2=00000000 CR3=00000000 CR4=00000000
CCS=0f8ee990 CCD=0f8efa5c CCO=ADDL    
FCW=037f FSW=0000 [ST=0] FTW=00 MXCSR=00001f80
FPR0=0000000000000000 0000 FPR1=0000000000000000 0000
FPR2=0000000000000000 0000 FPR3=0000000000000000 0000
FPR4=0000000000000000 0000 FPR5=0000000000000000 0000
FPR6=0000000000000000 0000 FPR7=0000000000000000 0000
XMM00=00000000000000000000000000000000 XMM01=00000000000000000000000000000000
XMM02=00000000000000000000000000000000 XMM03=00000000000000000000000000000000
XMM04=00000000000000000000000000000000 XMM05=00000000000000000000000000000000
XMM06=00000000000000000000000000000000 XMM07=00000000000000000000000000000000