linux-kernel - Re: [PATCH 26/27] KVM: x86/mmu: Add page-track API to query if a gfn is valid

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Message-ID: <Y7ZAEsQbNbWKngGi@yzhao56-desk.sh.intel.com>
Date:   Thu, 5 Jan 2023 11:12:18 +0800
From:   Yan Zhao <yan.y.zhao@...el.com>
To:     Sean Christopherson <seanjc@...gle.com>
CC:     Paolo Bonzini <pbonzini@...hat.com>,
        Zhenyu Wang <zhenyuw@...ux.intel.com>,
        Zhi Wang <zhi.a.wang@...el.com>, <kvm@...r.kernel.org>,
        <intel-gvt-dev@...ts.freedesktop.org>,
        <intel-gfx@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>,
        Ben Gardon <bgardon@...gle.com>
Subject: Re: [PATCH 26/27] KVM: x86/mmu: Add page-track API to query if a gfn
 is valid

On Tue, Jan 03, 2023 at 09:19:01PM +0000, Sean Christopherson wrote:
> On Wed, Dec 28, 2022, Yan Zhao wrote:
> > On Fri, Dec 23, 2022 at 12:57:38AM +0000, Sean Christopherson wrote:
> > > +bool kvm_page_track_is_valid_gfn(struct kvm *kvm, gfn_t gfn)
> > > +{
> > > +	bool ret;
> > > +	int idx;
> > > +
> > > +	idx = srcu_read_lock(&kvm->srcu);
> > > +	ret = kvm_is_visible_gfn(kvm, gfn);
> > > +	srcu_read_unlock(&kvm->srcu, idx);
> > > +
> > > +	return ret;
> > > +}
> > > +EXPORT_SYMBOL_GPL(kvm_page_track_is_valid_gfn);
> > This implementation is only to check whether a GFN is within a visible
> > kvm memslot. So, why this helper function is named kvm_page_track_xxx()?
> > Don't think it's anything related to page track, and not all of its callers
> > in KVMGT are for page tracking.
> 
> KVMGT is the only user of kvm_page_track_is_valid_gfn().  kvm_is_visible_gfn()
> has other users, just not in x86.  And long term, my goal is to allow building
> KVM x86 without any exports.  Killing off KVM's "internal" (for vendor modules)
> exports for select Kconfigs is easy enough, add adding a dedicated page-track API
> solves the KVMGT angle.
Understand!
But personally, I don't like merging this API into page-track API as
it obviously has nothing to do with page-track stuffs, and KVMGT also calls it for
non-page-track purpuse.