linux-kernel - Re: [RFC PATCH v3 14/19] KVM: x86: rename .set_apic_access_page_addr to reload_apic_access

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Date:   Thu, 19 May 2022 16:55:18 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Maxim Levitsky <mlevitsk@...hat.com>
Cc:     kvm@...r.kernel.org, Wanpeng Li <wanpengli@...cent.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Zhenyu Wang <zhenyuw@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Ingo Molnar <mingo@...hat.com>,
        David Airlie <airlied@...ux.ie>,
        Thomas Gleixner <tglx@...utronix.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        intel-gfx@...ts.freedesktop.org, Daniel Vetter <daniel@...ll.ch>,
        Borislav Petkov <bp@...en8.de>, Joerg Roedel <joro@...tes.org>,
        linux-kernel@...r.kernel.org, Jim Mattson <jmattson@...gle.com>,
        Zhi Wang <zhi.a.wang@...el.com>,
        Brijesh Singh <brijesh.singh@....com>,
        "H. Peter Anvin" <hpa@...or.com>,
        intel-gvt-dev@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org
Subject: Re: [RFC PATCH v3 14/19] KVM: x86: rename .set_apic_access_page_addr
 to reload_apic_access_page

On Wed, Apr 27, 2022, Maxim Levitsky wrote:
> This will be used on SVM to reload shadow page of the AVIC physid table
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index d2f73ce87a1e3..ad744ab99734c 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -9949,12 +9949,12 @@ void kvm_arch_mmu_notifier_invalidate_range(struct kvm *kvm,
>  		kvm_make_all_cpus_request(kvm, KVM_REQ_APIC_PAGE_RELOAD);
>  }
>  
> -static void kvm_vcpu_reload_apic_access_page(struct kvm_vcpu *vcpu)
> +static void kvm_vcpu_reload_apic_pages(struct kvm_vcpu *vcpu)
>  {
>  	if (!lapic_in_kernel(vcpu))
>  		return;
>  
> -	static_call_cond(kvm_x86_set_apic_access_page_addr)(vcpu);
> +	static_call_cond(kvm_x86_reload_apic_pages)(vcpu);
>  }
>  
>  void __kvm_request_immediate_exit(struct kvm_vcpu *vcpu)
> @@ -10071,7 +10071,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
>  		if (kvm_check_request(KVM_REQ_LOAD_EOI_EXITMAP, vcpu))
>  			vcpu_load_eoi_exitmap(vcpu);
>  		if (kvm_check_request(KVM_REQ_APIC_PAGE_RELOAD, vcpu))
> -			kvm_vcpu_reload_apic_access_page(vcpu);
> +			kvm_vcpu_reload_apic_pages(vcpu);

My vote is to add a new request and new kvm_x86_ops hook instead of piggybacking
KVM_REQ_APIC_PAGE_RELOAD.  The usage in kvm_arch_mmu_notifier_invalidate_range()
very subtlies relies on the memslot and vma being allocated/controlled by KVM.

The use in avic_physid_shadow_table_flush_memslot() is too similar in that it
also deals with memslot changes, but at the same time is _very_ different in that
it's dealing with user controlled memslots.