Re: [PATCH v2 1/2] x86/traps: Initialize DR6 by writing its architectural reset value

[Maciej W. Rozycki]

On Tue, 17 Jun 2025, Sean Christopherson wrote:

> Yeah, the name is weird, but IMO DR6_INIT or DR6_RESET aren't great either.  I'm
> admittedly very biased, but I think KVM's DR6_ACTIVE_LOW better captures the
> behavior of the bits.  E.g. even if bits that are currently reserved become defined
> in the future, they'll still need to be active low so as to be backwards compatible
> with existing software.

 FWIW I'd call this macro DR6_DEFAULT, to keep it simple and explicitly 
express our intent here (we want to set our default after all).

 I think reusing DR6_ACTIVE_LOW could be risky, regardless of its KVM use, 
because there's no guarantee the semantics of a future architectural 
addition will match the name, i.e. the value of 0 may actually *disable* 
what we currently have always enabled and while technically this could 
count as "feature active", this double-negation might just make one's head 
spin unnecessarily.  Plus we may actually want to have that stuff disabled 
by default then.

  Maciej