Re: [RESEND PATCH 1/2] KVM: X86: Add support for the emulation of DR6_BUS_LOCK bit

[Xiaoyao Li]

On 1/27/2021 12:31 AM, Paolo Bonzini wrote:
> On 08/01/21 07:49, Chenyi Qiang wrote:
> > To avoid breaking the CPUs without bus lock detection, activate the
> > DR6_BUS_LOCK bit (bit 11) conditionally in DR6_FIXED_1 bits.
> >
> > The set/clear of DR6_BUS_LOCK is similar to the DR6_RTM in DR6
> > register. The processor clears DR6_BUS_LOCK when bus lock debug
> > exception is generated. (For all other #DB the processor sets this bit
> > to 1.) Software #DB handler should set this bit before returning to the
> > interrupted task.
> >
> > For VM exit caused by debug exception, bit 11 of the exit qualification
> > is set to indicate that a bus lock debug exception condition was
> > detected. The VMM should emulate the exception by clearing bit 11 of the
> > guest DR6.
>
> Please rename DR6_INIT to DR6_ACTIVE_LOW, and then a lot of changes 
> become simpler:

Paolo,

What do you want to convey with the new name DR6_ACTIVE_LOW? To be 
honest, the new name is confusing to me.

> > -        dr6 |= DR6_BD | DR6_RTM;
> > +        dr6 |= DR6_BD | DR6_RTM | DR6_BUS_LOCK;
>
> dr6 |= DR6_BD | DR6_ACTIVE_LOW;