RE: [PATCH v6 00/12] SVM cleanup and INVPCID feature support

Babu Moger
2021-03-10T01:05:29Z

> -----Original Message-----
> From: Babu Moger <babu.moger@amd.com>
> Sent: Wednesday, February 24, 2021 4:17 PM
> To: Jim Mattson <jmattson@google.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>; Vitaly Kuznetsov
> <vkuznets@redhat.com>; Wanpeng Li <wanpengli@tencent.com>; kvm list
> <kvm@vger.kernel.org>; Joerg Roedel <joro@8bytes.org>; the arch/x86
> maintainers <x86@kernel.org>; LKML <linux-kernel@vger.kernel.org>; Ingo
> Molnar <mingo@redhat.com>; Borislav Petkov <bp@alien8.de>; H . Peter
> Anvin <hpa@zytor.com>; Thomas Gleixner <tglx@linutronix.de>; Makarand
> Sonare <makarandsonare@google.com>; Sean Christopherson
> <seanjc@google.com>
> Subject: RE: [PATCH v6 00/12] SVM cleanup and INVPCID feature support
>
>
>
> > -----Original Message-----
> > From: Jim Mattson <jmattson@google.com>
> > Sent: Tuesday, February 23, 2021 6:14 PM
> > To: Moger, Babu <Babu.Moger@amd.com>
> > Cc: Paolo Bonzini <pbonzini@redhat.com>; Vitaly Kuznetsov
> > <vkuznets@redhat.com>; Wanpeng Li <wanpengli@tencent.com>; kvm list
> > <kvm@vger.kernel.org>; Joerg Roedel <joro@8bytes.org>; the arch/x86
> > maintainers <x86@kernel.org>; LKML <linux-kernel@vger.kernel.org>;
> > Ingo Molnar <mingo@redhat.com>; Borislav Petkov <bp@alien8.de>; H .
> > Peter Anvin <hpa@zytor.com>; Thomas Gleixner <tglx@linutronix.de>;
> > Makarand Sonare <makarandsonare@google.com>; Sean Christopherson
> > <seanjc@google.com>
> > Subject: Re: [PATCH v6 00/12] SVM cleanup and INVPCID feature support
> >
> > Any updates? What should we be telling customers with Debian 9 guests?
> > :-)
>
> Found another problem with pcid feature om SVM. It is do with CR4 flags
> reset during bootup. Problem was showing up with kexec loading on VM.
> I am not sure if this is related to that. Will send the patch soon.

Tried to reproduce the problem on upstream kernel versions without any
success. Tried v4.9-0 and v4.8-0. Both these upstream versions are
working fine. So "git bisect" on upstream is ruled out.

Debian kernel 4.10(tag 4.10~rc6-1~exp1) also works fine. It appears the
problem is on Debian 4.9 kernel. I am not sure how to run git bisect on
Debian kernel. Tried anyway. It is pointing to

47811c66356d875e76a6ca637a9d384779a659bb is the first bad commit
commit 47811c66356d875e76a6ca637a9d384779a659bb
Author: Ben Hutchings <benh@debian.org>
Date: Mon Mar 8 01:17:32 2021 +0100

Prepare to release linux (4.9.258-1).

It does not appear to be the right commit. I am out of ideas now.
hanks
Babu

>
> >
> > On Fri, Jan 22, 2021 at 5:52 PM Babu Moger <babu.moger@amd.com>
> wrote:
> > >
> > >
> > >
> > > On 1/21/21 5:51 PM, Babu Moger wrote:
> > > >
> > > >
> > > > On 1/20/21 9:10 PM, Babu Moger wrote:
> > > >>
> > > >>
> > > >> On 1/20/21 3:45 PM, Babu Moger wrote:
> > > >>>
> > > >>>
> > > >>> On 1/20/21 3:14 PM, Jim Mattson wrote:
> > > >>>> On Tue, Jan 19, 2021 at 3:45 PM Babu Moger
> <babu.moger@amd.com>
> > wrote:
> > > >>>>>
> > > >>>>>
> > > >>>>>
> > > >>>>> On 1/19/21 5:01 PM, Jim Mattson wrote:
> > > >>>>>> On Mon, Sep 14, 2020 at 11:33 AM Babu Moger
> > <babu.moger@amd.com> wrote:
> > > >>>>>>
> > > >>>>>>> Thanks Paolo. Tested Guest/nested guest/kvm units tests.
> > > >>>>>>> Everything works as expected.
> > > >>>>>>
> > > >>>>>> Debian 9 does not like this patch set. As a kvm guest, it
> > > >>>>>> panics on a Milan CPU unless booted with 'nopcid'. Gmail
> > > >>>>>> mangles long lines, so please see the attached kernel log
> > > >>>>>> snippet. Debian 10 is fine, so I assume this is a guest bug.
> > > >>>>>>
> > > >>>>>
> > > >>>>> We had an issue with PCID feature earlier. This was showing
> > > >>>>> only with SEV guests. It is resolved recently. Do you think it
> > > >>>>> is not related
> > that?
> > > >>>>> Here are the patch set.
> > > >>>>>
> https://nam11.safelinks.protection.outlook.com/?url=https%3A%2
> > > >>>>> F%25
> > > >>>>>
> > 2Flore.kernel.org%2Fkvm%2F160521930597.32054.4906933314022910996
> > > >>>>> .stgit%40bmoger-
> > ubuntu%2F&amp;data=04%7C01%7Cbabu.moger%40amd.co
> > > >>>>>
> >
> m%7C9558672ca21c4f6c2d5308d8d85919dc%7C3dd8961fe4884e608e11a82d9
> > > >>>>>
> >
> 94e183d%7C0%7C0%7C637497224490455772%7CUnknown%7CTWFpbGZsb3d
> 8
> > eyJ
> > > >>>>>
> >
> WIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%
> > > >>>>>
> >
> 7C1000&amp;sdata=4QzTNHaYllwPd1U0kumq75dpwp7Rg0ZXsSQ631jMeqs%
> 3D
> > &
> > > >>>>> amp;reserved=0
> > > >>>>
> > > >>>> The Debian 9 release we tested is not an SEV guest.
> > > >>> ok. I have not tested Debian 9 before. I will try now. Will let
> > > >>> you know how it goes. thanks
> > > >>>
> > > >>
> > > >> I have reproduced the issue locally. Will investigate. thanks
> > > >>
> > > > Few updates.
> > > > 1. Like Jim mentioned earlier, this appears to be guest kernel issue.
> > > > Debian 9 runs the base kernel 4.9.0-14. Problem can be seen
> > > > consistently with this kernel.
> > > >
> > > > 2. This guest kernel(4.9.0-14) does not like the new feature INVPCID.
> > > >
> > > > 3. System comes up fine when invpcid feature is disabled with the
> > > > boot parameter "noinvpcid" and also with "nopcid". nopcid disables
> > > > both pcid and invpcid.
> > > >
> > > > 4. Upgraded the guest kernel to v5.0 and system comes up fine.
> > > >
> > > > 5. Also system comes up fine with latest guest kernel 5.11.0-rc4.
> > > >
> > > > I did not bisect further yet.
> > > > Babu
> > > > Thanks
> > >
> > >
> > > Some more update:
> > > System comes up fine with kernel v4.9(checked out on upstream tag
> v4.9).
> > > So, I am assuming this is something specific to Debian 4.9.0-14 kernel.
> > >
> > > Note: I couldn't go back prior versions(v4.8 or earlier) due to
> > > compile issues.
> > > Thanks
> > > Babu
> > >