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

From: Paolo Bonzini
Date: Tue Aug 10 2021 - 08:50:03 EST


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