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


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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