linux-kernel - Re: [PATCH v4 07/17] svm: Add support for setup/destroy virutal APIC backing page for AVIC

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Date:   Mon, 4 Nov 2019 21:53:51 +0000
From:   Roman Kagan <rkagan@...tuozzo.com>
To:     "Suthikulpanit, Suravee" <Suravee.Suthikulpanit@....com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "rkrcmar@...hat.com" <rkrcmar@...hat.com>,
        "joro@...tes.org" <joro@...tes.org>,
        "vkuznets@...hat.com" <vkuznets@...hat.com>,
        "graf@...zon.com" <graf@...zon.com>,
        "jschoenh@...zon.de" <jschoenh@...zon.de>,
        "karahmed@...zon.de" <karahmed@...zon.de>,
        "rimasluk@...zon.com" <rimasluk@...zon.com>,
        "Grimm, Jon" <Jon.Grimm@....com>
Subject: Re: [PATCH v4 07/17] svm: Add support for setup/destroy virutal APIC
 backing page for AVIC

On Fri, Nov 01, 2019 at 10:41:30PM +0000, Suthikulpanit, Suravee wrote:
> Re-factor avic_init_access_page() to avic_update_access_page() since
> activate/deactivate AVIC requires setting/unsetting the memory region used
> for virtual APIC backing page (APIC_ACCESS_PAGE_PRIVATE_MEMSLOT).

AFAICT the patch actually touches the (de)allocation of the APIC access
page rather than the APIC backing page (or I'm confused in the
nomenclature).

Thanks,
Roman.

> Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@....com>
> ---
>  arch/x86/kvm/svm.c | 11 +++++------
>  1 file changed, 5 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index b7d0adc..46842a2 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -1668,23 +1668,22 @@ static u64 *avic_get_physical_id_entry(struct kvm_vcpu *vcpu,
>   * field of the VMCB. Therefore, we set up the
>   * APIC_ACCESS_PAGE_PRIVATE_MEMSLOT (4KB) here.
>   */
> -static int avic_init_access_page(struct kvm_vcpu *vcpu)
> +static int avic_update_access_page(struct kvm *kvm, bool activate)
>  {
> -	struct kvm *kvm = vcpu->kvm;
>  	int ret = 0;
>  
>  	mutex_lock(&kvm->slots_lock);
> -	if (kvm->arch.apic_access_page_done)
> +	if (kvm->arch.apic_access_page_done == activate)
>  		goto out;
>  
>  	ret = __x86_set_memory_region(kvm,
>  				      APIC_ACCESS_PAGE_PRIVATE_MEMSLOT,
>  				      APIC_DEFAULT_PHYS_BASE,
> -				      PAGE_SIZE);
> +				      activate ? PAGE_SIZE : 0);
>  	if (ret)
>  		goto out;
>  
> -	kvm->arch.apic_access_page_done = true;
> +	kvm->arch.apic_access_page_done = activate;
>  out:
>  	mutex_unlock(&kvm->slots_lock);
>  	return ret;
> @@ -1697,7 +1696,7 @@ static int avic_init_backing_page(struct kvm_vcpu *vcpu)
>  	int id = vcpu->vcpu_id;
>  	struct vcpu_svm *svm = to_svm(vcpu);
>  
> -	ret = avic_init_access_page(vcpu);
> +	ret = avic_update_access_page(vcpu->kvm, true);
>  	if (ret)
>  		return ret;
>  
> -- 
> 1.8.3.1
>