Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <1593426391-8231-1-git-send-email-wanpengli@tencent.com>
 <877dvqc7cs.fsf@vitty.brq.redhat.com> <f9b06428-51c3-09af-48cc-d378182916fd@redhat.com>
 <20200629154212.GC12312@linux.intel.com>
In-Reply-To: <20200629154212.GC12312@linux.intel.com>
From:   Wanpeng Li <kernellwp@gmail.com>
Date:   Tue, 30 Jun 2020 08:16:41 +0800
Message-ID: <CANRm+Cx7-kEDKTSmoocgwRa+q30LdVhbaLth_dLss6wshAnOHg@mail.gmail.com>
Subject: Re: [PATCH] KVM: X86: Fix async pf caused null-ptr-deref
To:     Sean Christopherson <sean.j.christopherson@intel.com>
Cc:     Paolo Bonzini <pbonzini@redhat.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
        Joerg Roedel <joro@8bytes.org>,
        Vivek Goyal <vgoyal@redhat.com>,
        LKML <linux-kernel@vger.kernel.org>, kvm <kvm@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Mon, 29 Jun 2020 at 23:42, Sean Christopherson
<sean.j.christopherson@intel.com> wrote:
>
> On Mon, Jun 29, 2020 at 03:59:25PM +0200, Paolo Bonzini wrote:
> > On 29/06/20 15:46, Vitaly Kuznetsov wrote:
> > >> +  if (!lapic_in_kernel(vcpu))
> > >> +          return 1;
> > >> +
> > > I'm not sure how much we care about !lapic_in_kernel() case but this
> > > change should be accompanied with userspace changes to not expose
> > > KVM_FEATURE_ASYNC_PF_INT or how would the guest know that writing a
> > > legitimate value will result in #GP?
> >
> > Almost any pv feature is broken with QEMU if kernel_irqchip=off.  I
> > wouldn't bother and I am seriously thinking of dropping all support for
> > that, including:
>
> Heh, based on my limited testing, that could be "Almost everything is
> broken with Qemu if kernel_irqchip=off".

It is broken for several years. :)