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Subject: Re: [PATCH 4/7] KVM: SVM: hyper-v: Nested enlightenments in VMCB
To:     Vineeth Pillai <viremana@linux.microsoft.com>,
        Lan Tianyu <Tianyu.Lan@microsoft.com>,
        Michael Kelley <mikelley@microsoft.com>,
        Sean Christopherson <seanjc@google.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
        Joerg Roedel <joro@8bytes.org>, Wei Liu <wei.liu@kernel.org>,
        Stephen Hemminger <sthemmin@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>
Cc:     "H. Peter Anvin" <hpa@zytor.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "K. Y. Srinivasan" <kys@microsoft.com>, x86@kernel.org,
        kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-hyperv@vger.kernel.org
References: <cover.1617804573.git.viremana@linux.microsoft.com>
 <e9de12a81ab31613fb55d5c1308ca0ca050ced4c.1617804573.git.viremana@linux.microsoft.com>
From:   Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <5927967d-c5a2-6df9-9aff-4b92c207df09@redhat.com>
Date:   Thu, 8 Apr 2021 17:44:59 +0200
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On 07/04/21 16:41, Vineeth Pillai wrote:
> +#define VMCB_ALL_CLEAN_MASK (__CLEAN_MASK | (1U << VMCB_HV_NESTED_ENLIGHTENMENTS))
> +#else
> +#define VMCB_ALL_CLEAN_MASK __CLEAN_MASK
> +#endif

I think this should depend on whether KVM is running on top of Hyper-V; 
not on whether KVM is *compiled* with Hyper-V support.

So you should turn VMCB_ALL_CLEAN_MASK into a __read_mostly variable.

Paolo

>   /* TPR and CR2 are always written before VMRUN */
>   #define VMCB_ALWAYS_DIRTY_MASK	((1U << VMCB_INTR) | (1U << VMCB_CR2))
>   
> @@ -230,7 +251,7 @@ static inline void vmcb_mark_all_dirty(struct vmcb *vmcb)
>   
>   static inline void vmcb_mark_all_clean(struct vmcb *vmcb)
>   {
> -	vmcb->control.clean = ((1 << VMCB_DIRTY_MAX) - 1)
> +	vmcb->control.clean = VMCB_ALL_CLEAN_MASK
>   			       & ~VMCB_ALWAYS_DIRTY_MASK;
>   }