Re: [RFC PATCH v3 14/19] KVM: x86: rename .set_apic_access_page_addr to reload_apic_access_page

From: Sean Christopherson <seanjc@google.com>
To: Maxim Levitsky <mlevitsk@redhat.com>
Cc: Wanpeng Li <wanpengli@tencent.com>,
	kvm@vger.kernel.org, David Airlie <airlied@linux.ie>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	dri-devel@lists.freedesktop.org, "H. Peter Anvin" <hpa@zytor.com>,
	Brijesh Singh <brijesh.singh@amd.com>,
	Joerg Roedel <joro@8bytes.org>,
	x86@kernel.org, Ingo Molnar <mingo@redhat.com>,
	Zhi Wang <zhi.a.wang@intel.com>,
	Tom Lendacky <thomas.lendacky@amd.com>,
	intel-gfx@lists.freedesktop.org, Borislav Petkov <bp@alien8.de>,
	Rodrigo Vivi <rodrigo.vivi@intel.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	intel-gvt-dev@lists.freedesktop.org,
	Jim Mattson <jmattson@google.com>,
	Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>,
	linux-kernel@vger.kernel.org, Paolo Bonzini <pbonzini@redhat.com>,
	Vitaly Kuznetsov <vkuznets@redhat.com>
Subject: Re: [RFC PATCH v3 14/19] KVM: x86: rename .set_apic_access_page_addr to reload_apic_access_page
Date: Thu, 19 May 2022 16:55:18 +0000	[thread overview]
Message-ID: <YoZ2dh+ZujErT5nk@google.com> (raw)
In-Reply-To: <20220427200314.276673-15-mlevitsk@redhat.com>

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.