linux-kernel - Re: [PATCH 19/27] KVM: x86/mmu: Use page-track notifiers iff there are external users

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Message-ID: <ZNEni2XZuwiPgqaC@google.com>
Date:   Mon, 7 Aug 2023 10:19:07 -0700
From:   Sean Christopherson <seanjc@...gle.com>
To:     Like Xu <like.xu.linux@...il.com>
Cc:     kvm@...r.kernel.org, intel-gvt-dev@...ts.freedesktop.org,
        intel-gfx@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Yan Zhao <yan.y.zhao@...el.com>,
        Ben Gardon <bgardon@...gle.com>,
        Zhi Wang <zhi.a.wang@...el.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Zhenyu Wang <zhenyuw@...ux.intel.com>
Subject: Re: [PATCH 19/27] KVM: x86/mmu: Use page-track notifiers iff there
 are external users

On Mon, Aug 07, 2023, Like Xu wrote:
> On 23/12/2022 8:57 am, Sean Christopherson wrote:
> > +static inline void kvm_page_track_write(struct kvm_vcpu *vcpu, gpa_t gpa,
> > +					const u8 *new, int bytes)
> > +{
> > +	__kvm_page_track_write(vcpu, gpa, new, bytes);
> > +
> > +	kvm_mmu_track_write(vcpu, gpa, new, bytes);
> > +}
> 
> The kvm_mmu_track_write() is only used for x86, where the incoming parameter
> "u8 *new" has not been required since 0e0fee5c539b ("kvm: mmu: Fix race in
> emulated page table writes"), please help confirm if it's still needed ? Thanks.
> A minor clean up is proposed.

Hmm, unless I'm misreading things, KVMGT ultimately doesn't consume @new either.
So I think we can remove @new from kvm_page_track_write() entirely.

Feel free to send a patch, otherwise I'll get to it later this week.