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

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Message-ID: <fc78b7f2-70aa-29fa-95ca-d599f76c8f1a@redhat.com>
Date:   Mon, 15 Oct 2018 14:02:58 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Liran Alon <liran.alon@...cle.com>
Cc:     lantianyu1986@...il.com, Lan Tianyu <Tianyu.Lan@...rosoft.com>,
        christoffer.dall@....com, marc.zyngier@....com, linux@...linux.org,
        catalin.marinas@....com, will.deacon@....com, jhogan@...nel.org,
        ralf@...ux-mips.org, paul.burton@...s.com, paulus@...abs.org,
        benh@...nel.crashing.org, mpe@...erman.id.au, kys@...rosoft.com,
        haiyangz@...rosoft.com, sthemmin@...rosoft.com, mingo@...hat.com,
        hpa@...or.com, x86@...nel.org, rkrcmar@...hat.com,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        linux-kernel@...r.kernel.org, linux-mips@...ux-mips.org,
        kvm-ppc@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        devel@...uxdriverproject.org, kvm@...r.kernel.org,
        michael.h.kelley@...rosoft.com, vkuznets@...hat.com
Subject: Re: [PATCH V4 2/15] KVM/MMU: Add tlb flush with range helper function

On 14/10/2018 10:16, Thomas Gleixner wrote:
>>> +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.

That's true, on the other hand I have indeed a concerns with this patch:
this series is not bisectable at all, because all the new code is dead
until the very last patch.  Uses of the new feature should come _after_
the implementation.

I don't have any big problem with what Liran pointed out (and I can live
with the unused static functions that would warn with -Wunused, too),
but the above should be fixed in v5, basically by moving patches 12-15
at the beginning of the series.

Paolo