linux-kernel - Re: [PATCH 12/14] KVM: x86/mmu: Fold max_mapping_level() into kvm_mmu_hugepage

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Date:   Tue, 21 Jan 2020 16:12:46 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     Paul Mackerras <paulus@...abs.org>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Marc Zyngier <maz@...nel.org>,
        James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        kvm-ppc@...r.kernel.org, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        syzbot+c9d1fb51ac9d0d10c39d@...kaller.appspotmail.com,
        Andrea Arcangeli <aarcange@...hat.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Barret Rhoden <brho@...gle.com>,
        David Hildenbrand <david@...hat.com>,
        Jason Zeng <jason.zeng@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Liran Alon <liran.alon@...cle.com>,
        linux-nvdimm <linux-nvdimm@...ts.01.org>
Subject: Re: [PATCH 12/14] KVM: x86/mmu: Fold max_mapping_level() into
 kvm_mmu_hugepage_adjust()

On 08/01/20 21:24, Sean Christopherson wrote:
> -	level = host_pfn_mapping_level(vcpu, gfn, pfn);
> +	slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn);
> +	if (!memslot_valid_for_gpte(slot, true))
> +		return PT_PAGE_TABLE_LEVEL;

Following up on my remark to patch 7, this can also use
gfn_to_memslot_dirty_bitmap.

Paolo

> +
> +	max_level = min(max_level, kvm_x86_ops->get_lpage_level());
> +	for ( ; max_level > PT_PAGE_TABLE_LEVEL; max_level--) {
> +		if (!__mmu_gfn_lpage_is_disallowed(gfn, max_level, slot))
> +			break;
> +	}
> +
> +	if (max_level == PT_PAGE_TABLE_LEVEL)
> +		return PT_PAGE_TABLE_LEVEL;
> +
> +	level = host_pfn_mapping_level(vcpu, gfn, pfn, slot);
>  	if (level == PT_PAGE_TABLE_LEVEL)
>  		return level;
>  
> @@ -4182,8 +4172,6 @@ static int direct_page_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u32 error_code,
>  	if (lpage_disallowed)
>  		max_level = PT_PAGE_TABLE_LEVEL;
>  
> -	max_level = max_mapping_level(vcpu, gfn, max_level);
> -
>  	if (fast_page_fault(vcpu, gpa, error_code))
>  		return RET_PF_RETRY;
>  
> diff --git a/arch/x86/kvm/mmu/paging_tmpl.h b/arch/x86/kvm/mmu/paging_tmpl.h
> index 0560982eda8b..ea174d85700a 100644
> --- a/arch/x86/kvm/mmu/paging_tmpl.h
> +++ b/arch/x86/kvm/mmu/paging_tmpl.h
> @@ -817,8 +817,6 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gpa_t addr, u32 error_code,
>  	else
>  		max_level = walker.level;
>  
> -	max_level = max_mapping_level(vcpu, walker.gfn, max_level);
> -
>  	mmu_seq = vcpu->kvm->mmu_notifier_seq;
>  	smp_rmb();
>  
>