Re: [PATCH V2 2/3] KVM: X86: Set the hardware DR6 only when KVM_DEBUGREG_WONT_EXIT

Paolo Bonzini
2021-08-10T12:50:02Z

On 10/08/21 12:46, Lai Jiangshan wrote:
> I'm OK with it. But I don't think the sketched idea would cause DR6 to
> be marked uselessly as dirty in SVM. It doesn't mark it dirty if the
> value is unchanged, and the value is always DR6_ACTIVE_LOW except when
> it just clears KVM_DEBUGREG_WONT_EXIT.

It would be marked dirty if it is not DR6_ACTIVE_LOW, because it would
be set first to DR6_ACTIVE_LOW in svm_handle_exit and then set back to
the guest value on the next entry.

Paolo