From: Maxim Levitsky <mlevitsk@redhat.com>
To: Sean Christopherson <seanjc@google.com>
Cc: kvm@vger.kernel.org, Joerg Roedel <joro@8bytes.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
Borislav Petkov <bp@alien8.de>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
"maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)"
<x86@kernel.org>,
"open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)"
<linux-kernel@vger.kernel.org>, Jim Mattson <jmattson@google.com>,
Wanpeng Li <wanpengli@tencent.com>,
Paolo Bonzini <pbonzini@redhat.com>
Subject: Re: [PATCH] KVM: x86: fix 32 bit build
Date: Wed, 16 Jun 2021 21:59:50 +0300 [thread overview]
Message-ID: <1a6d4cc2152eebb5a0656e3718fc96645ee2e785.camel@redhat.com> (raw)
In-Reply-To: <YMof22ameZYUHNdi@google.com>
On Wed, 2021-06-16 at 15:59 +0000, Sean Christopherson wrote:
> On Wed, Jun 16, 2021, Maxim Levitsky wrote:
> > Now that kvm->stat.nx_lpage_splits is 64 bit, use DIV_ROUND_UP_ULL
> > when doing division.
>
> I went the "cast to an unsigned long" route. I prefer the cast approach because
> to_zap is also an unsigned long, i.e. using DIV_ROUND_UP_ULL() could look like a
> truncation bug. In practice, nx_lpage_splits can't be more than an unsigned long
> so it's largely a moot point, I just like the more explicit "this is doing
> something odd".
>
> https://lkml.kernel.org/r/20210615162905.2132937-1-seanjc@google.com
>
> > Fixes: 7ee093d4f3f5 ("KVM: switch per-VM stats to u64")
> > Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
> > ---
> > arch/x86/kvm/mmu/mmu.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> > index 720ceb0a1f5c..97372225f183 100644
> > --- a/arch/x86/kvm/mmu/mmu.c
> > +++ b/arch/x86/kvm/mmu/mmu.c
> > @@ -6054,7 +6054,7 @@ static void kvm_recover_nx_lpages(struct kvm *kvm)
> > write_lock(&kvm->mmu_lock);
> >
> > ratio = READ_ONCE(nx_huge_pages_recovery_ratio);
> > - to_zap = ratio ? DIV_ROUND_UP(kvm->stat.nx_lpage_splits, ratio) : 0;
> > + to_zap = ratio ? DIV_ROUND_UP_ULL(kvm->stat.nx_lpage_splits, ratio) : 0;
> > for ( ; to_zap; --to_zap) {
> > if (list_empty(&kvm->arch.lpage_disallowed_mmu_pages))
> > break;
> > --
> > 2.26.3
> >
Cool, makes sense.
I didn't notice your patch (I did look at the list but
since the subject didn't mention the build breakage I didn't notice).
I just wanted to send this patch to avoid someone else
spending time figuring it out.
Thanks,
Best regards,
Maxim Levitsky
prev parent reply other threads:[~2021-06-16 19:00 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-16 15:50 Maxim Levitsky
2021-06-16 15:59 ` Sean Christopherson
2021-06-16 18:59 ` Maxim Levitsky [this message]
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