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Subject: Re: [PATCH 6/7] KVM: SVM: hyper-v: Enlightened MSR-Bitmap support
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>
 <5cf935068a9539146e033276b6d9a6c9b1e42119.1617804573.git.viremana@linux.microsoft.com>
From:   Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <58df22aa-5d2c-f99f-6dfb-9a8b4260dc21@redhat.com>
Date:   Thu, 8 Apr 2021 17:47:15 +0200
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On 07/04/21 16:41, Vineeth Pillai wrote:
>   
> +#if IS_ENABLED(CONFIG_HYPERV)
> +static inline void hv_vmcb_dirty_nested_enlightenments(struct kvm_vcpu *vcpu)
> +{
> +	struct vmcb *vmcb = to_svm(vcpu)->vmcb;
> +
> +	/*
> +	 * vmcb can be NULL if called during early vcpu init.
> +	 * And its okay not to mark vmcb dirty during vcpu init
> +	 * as we mark it dirty unconditionally towards end of vcpu
> +	 * init phase.
> +	 */
> +	if (vmcb && vmcb_is_clean(vmcb, VMCB_HV_NESTED_ENLIGHTENMENTS) &&
> +	    vmcb->hv_enlightenments.hv_enlightenments_control.msr_bitmap)
> +		vmcb_mark_dirty(vmcb, VMCB_HV_NESTED_ENLIGHTENMENTS);
> +}

In addition to what Vitaly said, can svm->vmcb really be NULL?  If so it 
might be better to reorder initializations and skip the NULL check.

Paolo