Re: [Xen-devel] [BUGFIX][PATCH 3/4] hvm_save_one: return correct data.

[Don Slutz <dslutz@xxxxxxxxxxx>]

On 12/17/13 03:20, Jan Beulich wrote:
> > > > On 16.12.13 at 18:51, Don Slutz <dslutz@xxxxxxxxxxx> wrote:
> > I feel that the attached bugfix patch is simple enough to make it into 4.4
> > and also be back ported to stable branches.
> I would tend to agree on the 4.4 part of this, but afaict this is used
> for debugging purposes only, so I'm not so sure about backporting
> to stable branches. What is your rationale behind that request?
I would think that getting bad info during debugging to be important.  For 
example:

Before (i.e. correct data):

# xenctx 7 7
rip: ffffffff8006b2b0
flags: 00000246 i z p
rsp: ffff8100bfe6bef0
rax: 0000000000000000   rcx: 0000000000000000   rdx: 0000000000000000
rbx: ffffffff8006b287   rsi: 0000000000000001   rdi: ffffffff802f0658
rbp: 0000000000000007    r8: ffff8100bfe6a000    r9: 0000000000000039
r10: ffff8100b80a5b40   r11: ffff810037fe6100   r12: 00000000000000ff
r13: ffffffff803b4680   r14: 0000000000000700   r15: ffffffff803d6340
 cs: 0010        ss: 0018        ds: 0018        es: 0018
 fs: 0000 @ 0000000000000000
 gs: 0000 @ ffff8100bfe17340/0000000000000000
Code (instr addr ffffffff8006b2b0)
65 48 8b 04 25 10 00 00 00 8b 80 38 e0 ff ff a8 08 75 04 fb f4 <eb> 01 fb 65 48 
8b 04 25 10 00 00


Stack:
 ffffffff80048d19 00000000000000e0 ffffffff80076be6 ffffffff803d4360
 0000000000000000 0000000000000000 0000000000000000 0000000000000000
 0000000000000000 0000000000000000 0000000000000000 0000000000000000
 0000000000000000 0000000000000000 0000000000000000 0000000000000000
 0000000000000000 0000000000000000 0000000000000000 0000000000000000

Call Trace:
  [<ffffffff8006b2b0>] <--
  [<ffffffff80048d19>]
  [<ffffffff80076be6>]
  [<ffffffff803d4360>]

After offline of vcpu 1:

# xenctx 7 7
cs:eip: 0010:8006b2b0
flags: 00000246 i z p
ss:esp: 0018:bfe6bef0
eax: 00000000   ebx: 8006b287   ecx: 00000000   edx: 00000000
esi: 00000001   edi: 802f0658   ebp: 00000007
 ds:     0018    es:     0018    fs:     0000    gs:     0000
Code (instr addr ffffffff8006b2b0)
f0 53 ff 00 f0 53 ff 00 f0 53 ff 00 f0 53 ff 00 f0 53 ff 00 f0 <53> ff 00 f0 53 
ff 00 f0 53 ff 00


Stack:
 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000

Call Trace:
  [<ffffffff8006b2b0>] <--

As you can see, it now looks like VCPU 7 is in 32 bit mode when it is not.

   -Don Slutz
> Andrew, short of taking your intrusive (and not yet agreed upon)
> rework - would you agree Don's change at least is a sufficient
> improvement to include it irrespective of any intentions you might
> have with this code?
>
> Jan

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