On 04/08/2010 09:26 PM, Pekka Enberg wrote:
Hi!
I am working on a light-weight KVM userspace launcher for Linux and am
bit stuck with a guest Linux kernel restarting when it tries to enter
long mode.
The register dump looks like this:
penberg@tiger:~/vm$ ./kvm bzImage
KVM exit reason: 8 ("KVM_EXIT_SHUTDOWN")
Registers:
rip: 00000000001000ed rsp: 00000000005d54b8 flags: 0000000000010046
rax: 0000000080000001 rbx: 0000000001f2c000 rcx: 00000000c0000080
rdx: 0000000000000000 rsi: 0000000000013670 rdi: 0000000002408000
rbp: 0000000000100000 r8: 0000000000000000 r9: 0000000000000000
r10: 0000000000000000 r11: 0000000000000000 r12: 0000000000000000
r13: 0000000000000000 r14: 0000000000000000 r15: 0000000000000000
cr0: 0000000080000011 cr2: 00000000001000ed cr3: 0000000002402000
cr4: 0000000000000020 cr8: 0000000000000000
Segment registers:
register selector base limit type p dpl db s l g avl
cs 0010 0000000000000000 ffffffff 0b 1 0 1 1 0 1 0
ss 0018 0000000000000000 ffffffff 03 1 0 1 1 0 1 0
ds 0018 0000000000000000 ffffffff 03 1 0 1 1 0 1 0
es 0018 0000000000000000 ffffffff 03 1 0 1 1 0 1 0
fs 0018 0000000000000000 ffffffff 03 1 0 1 1 0 1 0
gs 0018 0000000000000000 ffffffff 03 1 0 1 1 0 1 0
tr 0020 0000000000001000 00000067 0b 1 0 0 0 0 0 0
ldt 0000 0000000000000000 ffffffff 00 0 0 0 0 0 0 0
These all look reasonable. Please add a gdtr dump and an idtr dump.
2b:* cb lret<-- trapping instruction
Post the two u32s at ss:rsp -> ss:rsp+8. That will tell us where the
guest is trying to return. Actually, from the dump:
1a: 6a 10 pushq $0x10
1c: 8d 85 00 02 00 00 lea 0x200(%rbp),%eax
22: 50 push %rax
it looks like you're returning to segment 0x10, this should be the word
at ss:rsp+4. So if you dump the 2 u32s at
gdtr.base+0x10..gdtr.base+0x18 we'll see if there's anything wrong with
the segment descriptor.
--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.
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