linux-kernel - Re: [PATCH 4.19 043/190] KVM: hyperv: define VP assist page helpers

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Date:   Sun, 15 Sep 2019 21:01:30 +0200
From:   Pavel Machek <pavel@...x.de>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Ladi Prosek <lprosek@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Liran Alon <liran.alon@...cle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sasha Levin <sashal@...nel.org>
Subject: Re: [PATCH 4.19 043/190] KVM: hyperv: define VP assist page helpers

On Fri 2019-09-13 14:04:58, Greg Kroah-Hartman wrote:
> [ Upstream commit 72bbf9358c3676bd89dc4bd8fb0b1f2a11c288fc ]
> 
> The state related to the VP assist page is still managed by the LAPIC
> code in the pv_eoi field.

I don't get it.

>  
> +bool kvm_hv_assist_page_enabled(struct kvm_vcpu *vcpu)
> +{
> +	if (!(vcpu->arch.hyperv.hv_vapic & HV_X64_MSR_VP_ASSIST_PAGE_ENABLE))
> +		return false;
> +	return vcpu->arch.pv_eoi.msr_val & KVM_MSR_ENABLED;
> +}
> +EXPORT_SYMBOL_GPL(kvm_hv_assist_page_enabled);
> +
> +bool kvm_hv_get_assist_page(struct kvm_vcpu *vcpu,
> +			    struct hv_vp_assist_page *assist_page)
> +{
> +	if (!kvm_hv_assist_page_enabled(vcpu))
> +		return false;
> +	return !kvm_read_guest_cached(vcpu->kvm, &vcpu->arch.pv_eoi.data,
> +				      assist_page, sizeof(*assist_page));
> +}
> +EXPORT_SYMBOL_GPL(kvm_hv_get_assist_page);
> +

This adds two functions, but not their users. What bug is it fixing? I
don't see any users in the next patch, either.

									Pavel


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