From: Sean Christopherson <sean.j.christopherson@intel.com>
To: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Jim Mattson <jmattson@google.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
kvm list <kvm@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] KVM: VMX: fix crash cleanup when KVM wasn't used
Date: Wed, 2 Sep 2020 08:18:48 -0700 [thread overview]
Message-ID: <20200902151848.GA11695@sjchrist-ice> (raw)
In-Reply-To: <87pn75wzpj.fsf@vitty.brq.redhat.com>
On Tue, Sep 01, 2020 at 12:36:40PM +0200, Vitaly Kuznetsov wrote:
> Sean Christopherson <sean.j.christopherson@intel.com> writes:
>
> > On Mon, Aug 24, 2020 at 03:45:26PM -0700, Jim Mattson wrote:
> >> On Mon, Aug 24, 2020 at 11:57 AM Jim Mattson <jmattson@google.com> wrote:
> >> >
> >> > On Fri, Aug 21, 2020 at 8:40 PM Sean Christopherson
> >> > <sean.j.christopherson@intel.com> wrote:
> >> > > I agree the code is a mess (kvm_init() and kvm_exit() included), but I'm
> >> > > pretty sure hardware_disable_nolock() is guaranteed to be a nop as it's
> >> > > impossible for kvm_usage_count to be non-zero if vmx_init() hasn't
> >> > > finished.
> >> >
> >> > Unless I'm missing something, there's no check for a non-zero
> >> > kvm_usage_count on this path. There is such a check in
> >> > hardware_disable_all_nolock(), but not in hardware_disable_nolock().
> >>
> >> However, cpus_hardware_enabled shouldn't have any bits set, so
> >> everything's fine. Nothing to see here, after all.
> >
> > Ugh, I forgot that hardware_disable_all_nolock() does a BUG_ON() instead of
> > bailing on !kvm_usage_count.
>
> But we can't hit this BUG_ON(), right? I'm failing to see how
> hardware_disable_all_nolock() can be reached with kvm_usage_count==0.
Correct, I was mostly talking to myself.
prev parent reply other threads:[~2020-09-02 15:34 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-01 8:13 [PATCH] KVM: VMX: fix crash cleanup when KVM wasn't used Vitaly Kuznetsov
2020-04-01 15:18 ` Sean Christopherson
2020-04-07 12:35 ` Paolo Bonzini
2020-04-09 1:22 ` Baoquan He
2020-08-20 20:08 ` Jim Mattson
2020-08-22 3:40 ` Sean Christopherson
2020-08-24 18:57 ` Jim Mattson
2020-08-24 22:45 ` Jim Mattson
2020-08-25 0:09 ` Sean Christopherson
2020-09-01 10:36 ` Vitaly Kuznetsov
2020-09-02 15:18 ` Sean Christopherson [this message]
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