linux-kernel - Re: [PATCH 3/11] KVM: Add spte's point in the struct kvm_mmu

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Message-ID: <dfaebf54-2a01-aafc-6f86-596f49874d3c@redhat.com>
Date:   Mon, 7 Jan 2019 17:34:00 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     lantianyu1986@...il.com
Cc:     kvm@...r.kernel.org, catalin.marinas@....com, will.deacon@....com,
        paulus@...abs.org, hpa@...or.com, kys@...rosoft.com,
        kvmarm@...ts.cs.columbia.edu, mpe@...erman.id.au, x86@...nel.org,
        linux@...linux.org.uk, michael.h.kelley@...rosoft.com,
        mingo@...hat.com, benh@...nel.crashing.org, jhogan@...nel.org,
        linux-mips@...r.kernel.org, Lan Tianyu <Tianyu.Lan@...rosoft.com>,
        marc.zyngier@....com, kvm-ppc@...r.kernel.org, bp@...en8.de,
        tglx@...utronix.de, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, ralf@...ux-mips.org,
        paul.burton@...s.com, vkuznets@...hat.com,
        linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH 3/11] KVM: Add spte's point in the struct kvm_mmu_page

On 04/01/19 09:53, lantianyu1986@...il.com wrote:
> @@ -332,6 +332,7 @@ struct kvm_mmu_page {
>  	int root_count;          /* Currently serving as active root */
>  	unsigned int unsync_children;
>  	struct kvm_rmap_head parent_ptes; /* rmap pointers to parent sptes */
> +	u64 *sptep;

Is this really needed?  Can we put the "last" flag in the struct instead
as a bool?  In fact, if you do

	u16 unsync_children;
	bool unsync;
	bool last_level;

the struct does not grow at all. :)

(I'm not sure where "large" is tested using the sptep field, even though
it is in the commit message).

Paolo

>  	/* The page is obsolete if mmu_valid_gen != kvm->arch.mmu_valid_gen.  */
>  	unsigned long mmu_valid_gen;