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Date:   Tue, 10 Aug 2021 14:49:54 +0200
From:   Paolo Bonzini <>
To:     Lai Jiangshan <>,
        Lai Jiangshan <>,
Cc:     Sean Christopherson <>,
        Vitaly Kuznetsov <>,
        Wanpeng Li <>,
        Jim Mattson <>,
        Joerg Roedel <>,
        Thomas Gleixner <>,
        Ingo Molnar <>, Borislav Petkov <>,, "H. Peter Anvin" <>,
Subject: Re: [PATCH V2 2/3] KVM: X86: Set the hardware DR6 only when

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.


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