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Date:   Mon, 29 Jun 2020 18:46:41 -0400 (EDT)
Subject: Re: [PATCH v2] Fix undefined operation VMXOFF during reboot and crash
From:   "David P. Reed" <dpreed@deepplum.com>
To:     "Sean Christopherson" <sean.j.christopherson@intel.com>
Cc:     "Andy Lutomirski" <luto@amacapital.net>,
        "Thomas Gleixner" <tglx@linutronix.de>,
        "Ingo Molnar" <mingo@redhat.com>, "Borislav Petkov" <bp@alien8.de>,
        "X86 ML" <x86@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>,
        "Allison Randal" <allison@lohutok.net>,
        "Enrico Weigelt" <info@metux.net>,
        "Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
        "Kate Stewart" <kstewart@linuxfoundation.org>,
        "=?utf-8?Q?Peter_Zijlstra_=28Intel=29?=" <peterz@infradead.org>,
        "Randy Dunlap" <rdunlap@infradead.org>,
        "Martin Molnar" <martin.molnar.programming@gmail.com>,
        "Andy Lutomirski" <luto@kernel.org>,
        "Alexandre Chartre" <alexandre.chartre@oracle.com>,
        "Jann Horn" <jannh@google.com>,
        "Dave Hansen" <dave.hansen@linux.intel.com>,
        "LKML" <linux-kernel@vger.kernel.org>
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=0A=0AOn Monday, June 29, 2020 5:49pm, "Sean Christopherson" <sean.j.christ=
opherson@intel.com> said:=0A=0A> On Mon, Jun 29, 2020 at 02:22:45PM -0700, =
Andy Lutomirski wrote:=0A>>=0A>>=0A>> > On Jun 29, 2020, at 1:54 PM, David =
P. Reed <dpreed@deepplum.com> wrote:=0A>> >=0A>> > =EF=BB=BFSimple question=
 for those on the To: and CC: list here. Should I=0A>> > abandon any hope o=
f this patch being accepted? It's been a long time.=0A>> >=0A>> > The non-r=
esponse after I acknowledged that this was discovered by when=0A>> > workin=
g on a personal, non-commercial research project - which is=0A>> > "out-of-=
tree" (apparently dirty words on LKML) has me thinking my=0A>> > contributi=
on is unwanted. That's fine, I suppose. I can maintain this patch=0A>> > ou=
t-of-tree as well.  I did incorporate all the helpful suggestions I=0A>> > =
received in this second patch, and given some encouragement, will happily=
=0A>> > submit a revised v3 if there is any likelihood of acceptance. I'm w=
ary of=0A>> > doing more radical changes (like combining emergency and norm=
al paths).=0A>> >=0A>>=0A>> Sorry about being slow and less actively encour=
aging than we should be. We=0A>> absolutely welcome personal contributions.=
 The actual problem is that=0A>> everyone is worked and we=E2=80=99re all s=
low. Also, you may be hitting a corner=0A>> case=0A>> in the process: is th=
is a KVM patch or an x86 patch?=0A> =0A> It's an x86 patch as it's not KVM =
specific, e.g. this code also helps play=0A> nice with out of tree hypervis=
ors.=0A> =0A> The code change is mostly good, but it needs to be split up a=
s there are=0A> three separate fixes:=0A> =0A>   1. Handle #UD on VMXON due=
 to a race.=0A>   2. Mark memory and flags as clobbered by VMXON.=0A>   3. =
Change emergency_vmx_disable_all() to not manually check cpu_vmx_enabled().=
=0A> =0A> Yes, the changes are tiny, but if for example #3 introduces a bug=
 then we=0A> don't have to revert #1 and #2.  Or perhaps older kernels are =
only subject=0A> to the #1 and #2 and thus dumping all three changes into a=
 single patch makes=0A> it all harder to backport.  In other words, all the=
 usual "one change per=0A> patch" reasons.=0A> =0AThanks. If no one else re=
sponds with additional suggestions, I will make it into 3 patches.=0AI'm ha=
ppy to learn the nuances of the kernel patch regimen.=0A=0A