linux-kernel - Re: [PATCH v2 07/11] KVM: x86/MMU: Factor out updating NX hugepages state for a VM

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Message-ID: <CANgfPd_XYoFAcrwkKE-fkS-wP7omNxC36fagT=OGaSE8Er3JXQ@mail.gmail.com>
Date:   Mon, 28 Mar 2022 15:41:18 -0700
From:   Ben Gardon <bgardon@...gle.com>
To:     David Matlack <dmatlack@...gle.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, kvm <kvm@...r.kernel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Peter Xu <peterx@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Jim Mattson <jmattson@...gle.com>,
        David Dunn <daviddunn@...gle.com>,
        Jing Zhang <jingzhangos@...gle.com>,
        Junaid Shahid <junaids@...gle.com>
Subject: Re: [PATCH v2 07/11] KVM: x86/MMU: Factor out updating NX hugepages
 state for a VM

On Mon, Mar 28, 2022 at 1:18 PM David Matlack <dmatlack@...gle.com> wrote:
>
> On Mon, Mar 21, 2022 at 04:48:40PM -0700, Ben Gardon wrote:
> > Factor out the code to update the NX hugepages state for an individual
> > VM. This will be expanded in future commits to allow per-VM control of
> > Nx hugepages.
> >
> > No functional change intended.
> >
> > Signed-off-by: Ben Gardon <bgardon@...gle.com>
> > ---
> >  arch/x86/kvm/mmu/mmu.c | 18 +++++++++++-------
> >  1 file changed, 11 insertions(+), 7 deletions(-)
> >
> > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> > index 3b8da8b0745e..1b59b56642f1 100644
> > --- a/arch/x86/kvm/mmu/mmu.c
> > +++ b/arch/x86/kvm/mmu/mmu.c
> > @@ -6195,6 +6195,15 @@ static void __set_nx_huge_pages(bool val)
> >       nx_huge_pages = itlb_multihit_kvm_mitigation = val;
> >  }
> >
> > +static int kvm_update_nx_huge_pages(struct kvm *kvm)
> > +{
> > +     mutex_lock(&kvm->slots_lock);
> > +     kvm_mmu_zap_all_fast(kvm);
> > +     mutex_unlock(&kvm->slots_lock);
> > +
> > +     wake_up_process(kvm->arch.nx_lpage_recovery_thread);
> > +}
> > +
> >  static int set_nx_huge_pages(const char *val, const struct kernel_param *kp)
> >  {
> >       bool old_val = nx_huge_pages;
> > @@ -6217,13 +6226,8 @@ static int set_nx_huge_pages(const char *val, const struct kernel_param *kp)
> >
> >               mutex_lock(&kvm_lock);
> >
>
> nit: This blank line is asymmetrical with mutex_unlock().
>
> > -             list_for_each_entry(kvm, &vm_list, vm_list) {
> > -                     mutex_lock(&kvm->slots_lock);
> > -                     kvm_mmu_zap_all_fast(kvm);
> > -                     mutex_unlock(&kvm->slots_lock);
> > -
> > -                     wake_up_process(kvm->arch.nx_lpage_recovery_thread);
> > -             }
> > +             list_for_each_entry(kvm, &vm_list, vm_list)
> > +                     kvm_set_nx_huge_pages(kvm);
>
> This should be kvm_update_nx_huge_pages() right?

Oh woops, duh. Apparently I did not compile-test this patch individually.

>
> >               mutex_unlock(&kvm_lock);
> >       }
> >
> > --
> > 2.35.1.894.gb6a874cedc-goog
> >