Hi 1. It seems that first problem happens because this particular double-word (address 0x9FFFD) is located on the boundary between regular memory and video memory. Probably this address accessed because some bug in that old kernel (I don't see any good reason to read this location). But it will be nice to check for reads/writes to such addresses.
2. Problem (oops) is gone away in rev 4571. Not sure why. Still it can be repeatedly reproduced on kvm-18. If needed, I can upload an image that reproduces these problems (~150MB compressed size). Thanks, Sergey -----Original Message----- From: Avi Kivity [mailto:[EMAIL PROTECTED] Sent: 27 March 2007 16:45 To: Kiselev, Sergey Cc: kvm-devel@lists.sourceforge.net Subject: Re: [kvm-devel] Physical memory read: word crosses page boundary + host kernel oops Kiselev, Sergey wrote: > Hi, > > 1. When booting old Linux (RH7.1 based, 2.4.9, 32bit) guest on kvm-18, > kvm userspace process crashes with 'Bus error' (last output on guest's > screen is "Uncompressing Linux..."). > I did some debugging and found that kvm_readl() function calls > ldl_phys() with address 0x9FFFD, so resulting double-word read crosses > page boundary. > After looking at qemu/exec.c it seems that ld*_phys and st*_phys > functions not really care about crossing page boundary (even there is > a comment sayng "warning: addr must be aligned"). So either > qemu/exec.c should be updated to check such condition or (more logical > place) qemu/qemu-kvm.c should take care of it. > > gdb backtrace: > (gdb) bt > #0 ldl_phys (addr=4093) at ../cpu-all.h:322 > #1 0x000000000047e08d in kvm_readl (opaque=0x9f, addr=159, > data=0x2b63605a5030) at /srv/src/kvm-18/qemu/qemu-kvm.c:543 This is quite surprising. I agree that hacking kvm_readl() is the best fix. > 2. After working-around the first issue, I have following problem: at > some point of guest's Linux boot sequence (after running > microcode_ctl, before running kudzu) following oops happens: > > > Mar 27 12:10:39 itstl140 kernel: Code: 4c 8b 08 41 0f 18 09 48 8d 70 > d8 31 c0 e9 39 ff ff ff 48 63 > Mar 27 12:10:39 itstl140 kernel: RIP > <ffffffff88366aa6>{:kvm:mmu_page_remove_parent_pte+225} RSP > <ffff81014e34f938> > Mar 27 12:10:39 itstl140 kernel: CR2: 000000030593a563 > I tried to disable both microcode_ctl and kudzu, in this case oops h Strangely, I've seen this exact oops somewhere booting Windows XP in safe mode. I haven't been able to reproduce it, though. If this is reproducible, it may be debugged by turning on audit (s/#undef AUDIT/#define AUDIT/ in mmu.c). Audit slows the guest down, but is a little faster if you reduce the amount of guest memory. If this is reproducible using a publicly available image, I may have a go at it too. -- error compiling committee.c: too many arguments to function ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys-and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
