Re: [Xen-users] HVM falls back to qemu emulation while VMX is enabled (Xen 3.1)

[Pim van Riezen <pi+lists@xxxxxxxxxxxx>]

On Oct 7, 2008, at 17:45 , Pim van Riezen wrote:

> On Oct 7, 2008, at 17:15 , Andrew Lyon wrote:
>
> > I don't think that is possible, afaik Xen can only run Windows  
> > through
> > HVM, there was a modified build of windows that was paravirtualized
> > but it was never released to the public, only some Xen developers at
> > cambridge university had access, so you are using vmx/hvm and your
> > problem is not that the cpu is being fully emulated, it is something
> > else!
> Ok, in that case let me restate my question without preconceptions  
> about its cause:
> I start the guest, it starts eating 100% cpu in xm top. It takes  
> forever booting and logging me into a desktop. It's the effect of  
> running on a severely underpowered CPU of a 386 class or lower. In  
> xentop, Domain-0 also seems to be taking up a lot of cpu, around  
> 70%. Running top in Dom0 shows qemu-md taking up that cpu-time.
In strace, qemu-dm seems to be stuck in this loop:

[pid  5591] read(14, "\33\0\0\0", 4)    = 4
[pid  5591] write(14, "\33\0\0\0", 4)   = 4
[pid  5591] clock_gettime(CLOCK_MONOTONIC, {8055, 225845018}) = 0
[pid  5591] ioctl(14, EVIOCGKEYCODE, 0x7fff49c8c900) = 0
[pid  5591] clock_gettime(CLOCK_MONOTONIC, {8055, 226550018}) = 0
[pid  5591] clock_gettime(CLOCK_MONOTONIC, {8055, 226601018}) = 0
[pid  5591] select(15, [8 9 10 12 14], [], [], {0, 10000}) = 1 (in  
[14], left {0, 10000})
qemu-dm 5591 root   14u   CHR               
10,63                            7412 /dev/xen/evtchn
A quick peek in gdb showed me these thread states:

Thread 3 (Thread 1100265792 (LWP 5634)):
#0  0x000000306300cc9b in read () from /lib64/libpthread.so.0
#1  0x00002ae56127997a in ?? () from /usr/lib64/libxenstore.so.3.0
#2  0x00002ae5612799f2 in ?? () from /usr/lib64/libxenstore.so.3.0
#3  0x00002ae561279b4c in ?? () from /usr/lib64/libxenstore.so.3.0
#4  0x0000003063006307 in start_thread () from /lib64/libpthread.so.0
#5  0x00000030628d1ded in clone () from /lib64/libc.so.6

Thread 2 (Thread 1114483008 (LWP 5709)):
#0  0x00000030628cb332 in select () from /lib64/libc.so.6
#1  0x000000000042bf31 in ?? ()
#2  0x0000003063006307 in start_thread () from /lib64/libpthread.so.0
#3  0x00000030628d1ded in clone () from /lib64/libc.so.6

Thread 1 (Thread 47164668008768 (LWP 5591)):
#0  0x00000030628ca9b7 in ioctl () from /lib64/libc.so.6
#1  0x00002ae560e2f0b6 in xc_evtchn_notify () from /usr/lib64/ 
libxenctrl.so.3.0
#2  0x000000000040950a in ?? ()
#3  0x000000000047152d in ?? ()
#4  0x000000000040afbb in ?? ()
#5  0x000000306281d8b4 in __libc_start_main () from /lib64/libc.so.6
#6  0x0000000000404939 in ?? ()
#7  0x00007fff49c90758 in ?? ()
#8  0x0000000000000000 in ?? ()
#0  0x00000030628ca9b7 in ioctl () from /lib64/libc.so.6

Hope that's useful :)

Cheers,
Pi

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