----- "Hu Tao" <hutao(a)cn.fujitsu.com&gt; wrote: > On Tue, Oct 19, 2010 at 09:06:33AM -0400, Dave Anderson wrote: > > > > ----- "Hu Tao" <hutao(a)cn.fujitsu.com&gt; wrote: > > > > > Hi Dave, > > > > > > These are updated patches tested with SMP system and panic > task. > > > > > > When testing a x86 guest, I found another bug about reading cpu > > > registers from dumpfile. Qemu simulated system is x86_64 > > > (qemu-system-x86_64), guest OS is x86. When crash reads cpu registers > > > from dumpfile, it uses cpu_load_32(), this will read gp registers by > > > get_be_long(fp, 32), that is, treate them as 32bits. But in fact, > > > qemu-system-x86_64 saves 64bits for each of them(although guest OS > > > uses only lower 32 bits). As a result, crash gets wrong cpu gp > > > register values. > > > > As I understand it, you're running a 32-bit guest on a 64-bit host. > > Yes. > > > If you were to read 64-bit register values instead of 32-bit register > > values, wouldn't that cause the file offsets of the subsequent get_xxx() > > calls in cpu_load() to read from the wrong file offsets? And then > > that would leave the ending file offset incorrect, such that the > > qemu_load() loop would fail to find the next device? > > > > In other words, the cpu_load() function, which is used for both > > 32-bit and 64-bit guests, must be reading the correct amount of > > data from the "cpu" device, or else qemu_load() would fail to > > find the next device in the next location in the dumpfile. > > True. In fact, in my case if read 32-bit registers, following devices > are found: > block, ram, kvm-tpr-opt, kvmclock, timer, cpu_common, cpu. > If read 64-bit registers, following devices are found: > block, ram, kvm-tpr-opt, kvmclock, timer, cpu_common, cpu, apic, fw_cfg Right -- so it got "lost" after incorrectly gathering the data for the first "cpu" device instance. > > > Is there any way we can know from dumpfile that these gp > > > registers(and those similar registers) are 32bits or 64bits? > > > > I don't know. If what you say is true, when would those registers > > ever be 32-bit values? > > I did tests on a 64-bit machine. Result is: > > machine OS guest machine guest OS saved gp regs > ------------------------------------------------------------------------ > 64-bit x86 qemu-kvm(kvm enabled) x86 64 bits > 64-bit x86 qemu(kvm disabled) x86 32 bits I don't understand what you mean when you say that the guest machine is "kvm enabled" or "kvm disabled"?

And if your host machine is running a 32-bit x86 OS (on 64-bit hardware), that's something I've never seen given that Red Hat only allows 64-bit kernels as KVM hosts.