Re: [Xen-devel] vmx_update_guest_cr() losing EXCEPTION_BITMAP setting

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

On 11/05/2009 05:32, "Byrne, John (HP Labs)" <john.l.byrne@xxxxxx> wrote:

> Running a heavily modified xen-unstable changset 19590:f80cf52a4fb6 with
> debugger_attached set, I was seeing the debug traps getting lost from the
> EXCEPTION_BITMAP in vmx_update_guest_cr() when transitioning from real to
> protected mode.  In my codebase, I could fix this trivially by clearing the
> debug_state_latch and letting vmx_do_resume() reapply the setting. However,
> while it looks like a valid issue in the unmodified codebase, I'm not sure. So
> maybe someone might test/examine it and decide if it is real and whether some
> more complex fix is required?

In vmx_update_guest_cr(), where EXCEPTION_BITMAP gets reset after exit from
real mode, try setting v->arch.hvm_vcpu.debug_state_latch=0 and
raise_softirq(SCHEDULE_SOFTIRQ).

 -- Keir



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