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

[Joerg Roedel <joerg.roedel@amd.com>]

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.

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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