linux-kernel - Re: [PATCH 4/7] KVM: SVM: hyper-v: Nested enlightenments in VMCB

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Date:   Thu, 8 Apr 2021 17:44:59 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Vineeth Pillai <viremana@...ux.microsoft.com>,
        Lan Tianyu <Tianyu.Lan@...rosoft.com>,
        Michael Kelley <mikelley@...rosoft.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, Wei Liu <wei.liu@...nel.org>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>
Cc:     "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "K. Y. Srinivasan" <kys@...rosoft.com>, x86@...nel.org,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-hyperv@...r.kernel.org
Subject: Re: [PATCH 4/7] KVM: SVM: hyper-v: Nested enlightenments in VMCB

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;
>   }