linux-kernel - Re: [RFC PATCH v12 11/33] KVM: Introduce per-page memory attributes

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Message-ID: <ZQteNbPfx6P3r6B8@google.com>
Date:   Wed, 20 Sep 2023 14:03:49 -0700
From:   Sean Christopherson <seanjc@...gle.com>
To:     Binbin Wu <binbin.wu@...ux.intel.com>
Cc:     kvm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        kvmarm@...ts.linux.dev, linux-mips@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, kvm-riscv@...ts.infradead.org,
        linux-riscv@...ts.infradead.org, linux-fsdevel@...r.kernel.org,
        linux-mm@...ck.org, linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
        Marc Zyngier <maz@...nel.org>,
        Oliver Upton <oliver.upton@...ux.dev>,
        Huacai Chen <chenhuacai@...nel.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Anup Patel <anup@...infault.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Paul Moore <paul@...l-moore.com>,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Chao Peng <chao.p.peng@...ux.intel.com>,
        Fuad Tabba <tabba@...gle.com>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        Anish Moorthy <amoorthy@...gle.com>,
        Yu Zhang <yu.c.zhang@...ux.intel.com>,
        Isaku Yamahata <isaku.yamahata@...el.com>,
        Xu Yilun <yilun.xu@...el.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Vishal Annapurve <vannapurve@...gle.com>,
        Ackerley Tng <ackerleytng@...gle.com>,
        Maciej Szmigiero <mail@...iej.szmigiero.name>,
        David Hildenbrand <david@...hat.com>,
        Quentin Perret <qperret@...gle.com>,
        Michael Roth <michael.roth@....com>,
        Wang <wei.w.wang@...el.com>,
        Liam Merwick <liam.merwick@...cle.com>,
        Isaku Yamahata <isaku.yamahata@...il.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: Re: [RFC PATCH v12 11/33] KVM: Introduce per-page memory attributes

On Mon, Sep 18, 2023, Binbin Wu wrote:
> 
> 
> On 9/14/2023 9:55 AM, Sean Christopherson wrote:
> > From: Chao Peng <chao.p.peng@...ux.intel.com>
> [...]
> > +#ifdef CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES
> > +/*
> > + * Returns true if _all_ gfns in the range [@start, @end) have attributes
> > + * matching @attrs.
> > + */
> > +bool kvm_range_has_memory_attributes(struct kvm *kvm, gfn_t start, gfn_t end,
> > +				     unsigned long attrs)
> > +{
> > +	XA_STATE(xas, &kvm->mem_attr_array, start);
> > +	unsigned long index;
> > +	bool has_attrs;
> > +	void *entry;
> > +
> > +	rcu_read_lock();
> > +
> > +	if (!attrs) {
> > +		has_attrs = !xas_find(&xas, end);
> IIUIC, xas_find() is inclusive for "end", so here should be "end - 1" ?

Yes, that does appear to be the case.  Inclusive vs. exclusive on gfn ranges has
is the bane of my existence.