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

Babu Moger
2021-02-24T22:18:26Z

> -----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.

>
> 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%2F%
> > >>>>>
> 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%7CTWFpbGZsb3d8
> 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
> >