Re: [PATCH 4/6] hw-breakpoints: Rewrite the hw-breakpoints layeron top of perf events

From: Frederic Weisbecker
Date: Tue Nov 03 2009 - 15:29:30 EST


On Tue, Nov 03, 2009 at 09:22:04PM +0100, Jan Kiszka wrote:
> > Thinking about it, this check should cover every cases:
> >
> > if (vcpu->arch.switch_db_regs || __get_cpu_var(dr7) & DR_GLOBAL_ENABLE_MASK)
> >
> > If we have __get_cpu_var(dr7) & DR_GLOBAL_ENABLE_MASK, it means there is an
> > active breakpoint and then we should restore the current state.
> >
>
> And what about (__get_cpu_var(dr7) & DR_GLOBAL_ENABLE_MASK) only? Would
> you be able to live with unsync'ed hardware and software states?
>
> Jan
>


But if the guest has breakpoints activated, the host will inherit
them, which is really not something we want, assuming vcpu->arch.switch_db_regs
already protects us about that.

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