Re: [PATCH V4 7/15] KVM/MMU: Flush tlb directly in the kvm_zap_gfn_range()

From: Tianyu Lan <lantianyu1986@gmail.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Tianyu Lan <Tianyu.Lan@microsoft.com>,
	kys@microsoft.com, haiyangz@microsoft.com,
	sthemmin@microsoft.com, Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
	"the arch/x86 maintainers" <x86@kernel.org>,
	Radim Krcmar <rkrcmar@redhat.com>,
	devel@linuxdriverproject.org,
	"linux-kernel@vger kernel org" <linux-kernel@vger.kernel.org>,
	kvm <kvm@vger.kernel.org>,
	michael.h.kelley@microsoft.com, vkuznets@redhat.com
Subject: Re: [PATCH V4 7/15] KVM/MMU: Flush tlb directly in the kvm_zap_gfn_range()
Date: Mon, 15 Oct 2018 21:08:32 +0800	[thread overview]
Message-ID: <CAOLK0pzrzydk9rk-Jijh=rA0oLkSafEqmumY2NSxe44J2=zv2A@mail.gmail.com> (raw)
In-Reply-To: <bdb05a65-f849-7346-61b7-99c444050254@redhat.com>

Hi Paolo:
              Thanks for your review.

On Mon, Oct 15, 2018 at 6:04 PM Paolo Bonzini <pbonzini@redhat.com> wrote:
>
> On 13/10/2018 16:53, lantianyu1986@gmail.com wrote:
> > +     bool flush = false;
> >       int i;
> >
> >       spin_lock(&kvm->mmu_lock);
> > @@ -5654,18 +5655,27 @@ void kvm_zap_gfn_range(struct kvm *kvm, gfn_t gfn_start, gfn_t gfn_end)
> >               slots = __kvm_memslots(kvm, i);
> >               kvm_for_each_memslot(memslot, slots) {
> >                       gfn_t start, end;
> > +                     bool flush_tlb = true;
> >
> >                       start = max(gfn_start, memslot->base_gfn);
> >                       end = min(gfn_end, memslot->base_gfn + memslot->npages);
> >                       if (start >= end)
> >                               continue;
> >
> > -                     slot_handle_level_range(kvm, memslot, kvm_zap_rmapp,
> > -                                             PT_PAGE_TABLE_LEVEL, PT_MAX_HUGEPAGE_LEVEL,
> > -                                             start, end - 1, true);
> > +                     if (kvm_available_flush_tlb_with_range())
> > +                             flush_tlb = false;
>
> This should be moved outside the for, because it's invariant.
>
> > +                     flush = slot_handle_level_range(kvm, memslot,
> > +                                     kvm_zap_rmapp, PT_PAGE_TABLE_LEVEL,
> > +                                     PT_MAX_HUGEPAGE_LEVEL, start,
> > +                                     end - 1, flush_tlb);
>
> ... and this should be "flush |= ".
> >               }
> >       }
> >
> > +     if (flush && kvm_available_flush_tlb_with_range())
> > +             kvm_flush_remote_tlbs_with_address(kvm, gfn_start,
> > +                             gfn_end - gfn_start + 1);
> > +
>
> ... and this can be just if (flush), because if flush_tlb is true then
> slot_handle_level_range always returns false.

OK. Will update.

-- 
Best regards
Tianyu Lan