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

From: Russell King - ARM Linux <linux@armlinux.org.uk>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Liran Alon <liran.alon@oracle.com>,
	linux-mips@linux-mips.org, linux@armlinux.org,
	kvm@vger.kernel.org, rkrcmar@redhat.com, catalin.marinas@arm.com,
	will.deacon@arm.com, linux-kernel@vger.kernel.org,
	paulus@ozlabs.org, hpa@zytor.com, kys@microsoft.com,
	kvmarm@lists.cs.columbia.edu, lantianyu1986@gmail.com,
	sthemmin@microsoft.com, mpe@ellerman.id.au, x86@kernel.org,
	michael.h.kelley@microsoft.com, mingo@redhat.com,
	benh@kernel.crashing.org, jhogan@kernel.org,
	Lan Tianyu <Tianyu.Lan@microsoft.com>,
	marc.zyngier@arm.com, haiyangz@microsoft.com,
	kvm-ppc@vger.kernel.org, devel@linuxdriverproject.org,
	linux-arm-kernel@lists.infradead.org, christoffer.dall@arm.com,
	ralf@linux-mips.org, paul.burton@mips.com, pbonzini@redhat.com,
	vkuznets@redhat.com, linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH V4 2/15] KVM/MMU: Add tlb flush with range helper function
Date: Sun, 14 Oct 2018 10:27:34 +0100	[thread overview]
Message-ID: <20181014092734.GV30658@n2100.armlinux.org.uk> (raw)
In-Reply-To: <alpine.DEB.2.21.1810141014350.1438@nanos.tec.linutronix.de>

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@gmail.com wrote:
> > > 
> > > From: Lan Tianyu <Tianyu.Lan@microsoft.com>
> > > 
> > > This patch is to add wrapper functions for tlb_remote_flush_with_range
> > > callback.
> > > 
> > > Signed-off-by: Lan Tianyu <Tianyu.Lan@microsoft.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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