linux-kernel - Re: [PATCH V4 2/15] KVM/MMU: Add tlb flush with range helper function

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Message-ID: <20181014092734.GV30658@n2100.armlinux.org.uk>
Date:   Sun, 14 Oct 2018 10:27:34 +0100
From:   Russell King - ARM Linux <linux@...linux.org.uk>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Liran Alon <liran.alon@...cle.com>, linux-mips@...ux-mips.org,
        linux@...linux.org, kvm@...r.kernel.org, rkrcmar@...hat.com,
        catalin.marinas@....com, will.deacon@....com,
        linux-kernel@...r.kernel.org, paulus@...abs.org, hpa@...or.com,
        kys@...rosoft.com, kvmarm@...ts.cs.columbia.edu,
        lantianyu1986@...il.com, sthemmin@...rosoft.com,
        mpe@...erman.id.au, x86@...nel.org, michael.h.kelley@...rosoft.com,
        mingo@...hat.com, benh@...nel.crashing.org, jhogan@...nel.org,
        Lan Tianyu <Tianyu.Lan@...rosoft.com>, marc.zyngier@....com,
        haiyangz@...rosoft.com, kvm-ppc@...r.kernel.org,
        devel@...uxdriverproject.org, linux-arm-kernel@...ts.infradead.org,
        christoffer.dall@....com, ralf@...ux-mips.org,
        paul.burton@...s.com, pbonzini@...hat.com, vkuznets@...hat.com,
        linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH V4 2/15] KVM/MMU: Add tlb flush with range helper function

On Sun, Oct 14, 2018 at 10:16:56AM +0200, Thomas Gleixner wrote:
> On Sun, 14 Oct 2018, Liran Alon wrote:
> > > On 13 Oct 2018, at 17:53, lantianyu1986@...il.com wrote:
> > > 
> > > From: Lan Tianyu <Tianyu.Lan@...rosoft.com>
> > > 
> > > This patch is to add wrapper functions for tlb_remote_flush_with_range
> > > callback.
> > > 
> > > Signed-off-by: Lan Tianyu <Tianyu.Lan@...rosoft.com>
> > > ---
> > > Change sicne V3:
> > >       Remove code of updating "tlbs_dirty"
> > > Change since V2:
> > >       Fix comment in the kvm_flush_remote_tlbs_with_range()
> > > ---
> > > arch/x86/kvm/mmu.c | 40 ++++++++++++++++++++++++++++++++++++++++
> > > 1 file changed, 40 insertions(+)
> > > 
> > > diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> > > index c73d9f650de7..ff656d85903a 100644
> > > --- a/arch/x86/kvm/mmu.c
> > > +++ b/arch/x86/kvm/mmu.c
> > > @@ -264,6 +264,46 @@ static void mmu_spte_set(u64 *sptep, u64 spte);
> > > static union kvm_mmu_page_role
> > > kvm_mmu_calc_root_page_role(struct kvm_vcpu *vcpu);
> > > 
> > > +
> > > +static inline bool kvm_available_flush_tlb_with_range(void)
> > > +{
> > > +	return kvm_x86_ops->tlb_remote_flush_with_range;
> > > +}
> > 
> > Seems that kvm_available_flush_tlb_with_range() is not used in this patch…
> 
> What's wrong with that? 
> 
> It provides the implementation and later patches make use of it. It's a
> sensible way to split patches into small, self contained entities.

>From what I can see of the patches that follow _this_ patch in the
series, this function remains unused.  So, not only is it not used
in this patch, it's not used in this series.

I think the real question that needs asking is - what is the plan
for this function, and when will it be used?

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
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