Re: [PATCH 1/3] KVM: x86 emulator: Fix task switch privilege checks

[Gleb Natapov <gleb@redhat.com>]

On Wed, Jan 25, 2012 at 05:00:58PM +0100, Joerg Roedel wrote:
> On Tue, Jan 24, 2012 at 06:23:50PM +0200, Gleb Natapov wrote:
> > On Tue, Jan 24, 2012 at 03:24:50PM +0100, Kevin Wolf wrote:
> 
> > > However, task_switch_interception() itself does some more based on the
> > > value of reason, for example it decides whether or not to call
> > > skip_emulated_instruction().
> > > 
> > Joerg need to help us here. If intercept of task switch happens before
> > rip is advanced past instruction that cause it we have to know somehow
> > that task switch was caused by instruction. It is not enough that HW
> > checks permission, we still lack essential info.
> 
> Hmm, the RIP in the VMCB points to the instruction causing the task
> switch. This is also true for lcall and ljmp. But in my experiments I
> have seen exit_int_info.valid = 1 for task-switches that went through
> the IDT. But I havn't tested the VM86 case, though.
> 
I can confirm that I get exit_int_info.valid = 1 for all scenarios when
task switch is caused by idt event. Just checked it here.

> Kevin, can you please re-verify that exit_int_info.valid is always 0 in
> your experiment? On what hardware have you tested this?
> 
> Thanks,
> 
> 	Joerg
> 
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			Gleb.