Re: [Xen-devel] [PATCH] x86/HVM: correct notion of new CPL in task switch emulation

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 02.06.17 at 22:33, <andrew.cooper3@xxxxxxxxxx> wrote:
> On 02/06/17 21:02, Andrew Cooper wrote:
>> On 01/06/17 13:11, Jan Beulich wrote:
>>> Reported-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
>>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
>> I have finally managed to reproduce the original vmentry failure with an
>> XTF test.
> 
> FWIW, the vmentry failure is quite subtle.
> 
> %es gets reloaded first.  If the new TSS uses RPL0 data selectors, the
> load fails, and #TS[%es] is yielded.
> 
> (d3) Going to userspace
> (XEN) ** d3v0 Inject event { v 0x02, t 2, ec ffffffff }
> (XEN) ** d3v0 Inject event { v 0x0a, t 3, ec 0018 }
> (XEN) ** d3v0 Inject event { v 0x0a, t 3, ec 0018 }
> (XEN) d3v0 Triple fault - invoking HVM shutdown action 1
> (XEN) *** Dumping Dom3 vcpu#0 state: ***
> (XEN) ----[ Xen-4.10-unstable  x86_64  debug=y   Tainted:    H ]----
> 
> For some reason I haven't gotten to the bottom of yet, end up calling
> __vmx_inject_exception() twice while handling the task switch path.  We
> shouldn't be.

There's no sign of #DF above - how are you handling that? Is the
above perhaps a 2nd task switch to handle #DF?

Jan


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