linux-kernel - Re: [RFC PATCH v2 51/69] KVM: x86/mmu: Allow per-VM override of the TDP max page level

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Message-ID: <89d1ff17-dc48-0f39-257a-4cf11a98f435@redhat.com>
Date:   Tue, 6 Jul 2021 16:58:57 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     isaku.yamahata@...el.com, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, erdemaktas@...gle.com,
        Connor Kuehl <ckuehl@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     isaku.yamahata@...il.com,
        Sean Christopherson <sean.j.christopherson@...el.com>
Subject: Re: [RFC PATCH v2 51/69] KVM: x86/mmu: Allow per-VM override of the
 TDP max page level

On 03/07/21 00:04, isaku.yamahata@...el.com wrote:
> From: Sean Christopherson <sean.j.christopherson@...el.com>
> 
> TODO: This is tentative patch.  Support large page and delete this patch.
> 
> Allow TDX to effectively disable large pages, as SEPT will initially
> support only 4k pages.
> 
> Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
> ---
>   arch/x86/include/asm/kvm_host.h | 1 +
>   arch/x86/kvm/mmu/mmu.c          | 4 +++-
>   2 files changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 9631b985ebdc..a47e17892258 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -989,6 +989,7 @@ struct kvm_arch {
>   	unsigned long n_requested_mmu_pages;
>   	unsigned long n_max_mmu_pages;
>   	unsigned int indirect_shadow_pages;
> +	int tdp_max_page_level;
>   	u8 mmu_valid_gen;
>   	struct hlist_head mmu_page_hash[KVM_NUM_MMU_PAGES];
>   	struct list_head active_mmu_pages;
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 82db62753acb..4ee6d7803f18 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -4084,7 +4084,7 @@ int kvm_tdp_page_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u32 error_code,
>   	kvm_pfn_t pfn;
>   	int max_level;
>   
> -	for (max_level = KVM_MAX_HUGEPAGE_LEVEL;
> +	for (max_level = vcpu->kvm->arch.tdp_max_page_level;
>   	     max_level > PG_LEVEL_4K;
>   	     max_level--) {
>   		int page_num = KVM_PAGES_PER_HPAGE(max_level);
> @@ -5802,6 +5802,8 @@ void kvm_mmu_init_vm(struct kvm *kvm)
>   	node->track_write = kvm_mmu_pte_write;
>   	node->track_flush_slot = kvm_mmu_invalidate_zap_pages_in_memslot;
>   	kvm_page_track_register_notifier(kvm, node);
> +
> +	kvm->arch.tdp_max_page_level = KVM_MAX_HUGEPAGE_LEVEL;
>   }
>   
>   void kvm_mmu_uninit_vm(struct kvm *kvm)
> 

Seems good enough for now.

Reviewed-by: Paolo Bonzini <pbonzini@...hat.com>

Paolo