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Date: Mon, 15 Jun 2020 14:15:24 +0200 From: Borislav Petkov <bp@...en8.de> To: Sean Christopherson <sean.j.christopherson@...el.com>, Greg KH <gregkh@...uxfoundation.org>, Sasha Levin <sashal@...nel.org> Cc: Liam Merwick <liam.merwick@...cle.com>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, x86@...nel.org, "Rafael J. Wysocki" <rjw@...ysocki.net>, Pavel Machek <pavel@....cz>, "H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org, Brad Campbell <lists2009@...rfbargle.com>, Maxim Levitsky <mlevitsk@...hat.com>, Paolo Bonzini <pbonzini@...hat.com>, kvm@...r.kernel.org Subject: Re: [PATCH] x86/cpu: Reinitialize IA32_FEAT_CTL MSR on BSP during wakeup On Mon, Jun 08, 2020 at 10:29:21AM -0700, Sean Christopherson wrote: > On Mon, Jun 08, 2020 at 11:12:35AM +0100, Liam Merwick wrote: > > On 05/06/2020 21:07, Sean Christopherson wrote: > > >Reinitialize IA32_FEAT_CTL on the BSP during wakeup to handle the case > > >where firmware doesn't initialize or save/restore across S3. This fixes > > >a bug where IA32_FEAT_CTL is left uninitialized and results in VMXON > > >taking a #GP due to VMX not being fully enabled, i.e. breaks KVM. > > > > > >Use init_ia32_feat_ctl() to "restore" IA32_FEAT_CTL as it already deals > > >with the case where the MSR is locked, and because APs already redo > > >init_ia32_feat_ctl() during suspend by virtue of the SMP boot flow being > > >used to reinitialize APs upon wakeup. Do the call in the early wakeup > > >flow to avoid dependencies in the syscore_ops chain, e.g. simply adding > > >a resume hook is not guaranteed to work, as KVM does VMXON in its own > > >resume hook, kvm_resume(), when KVM has active guests. > > > > > >Reported-by: Brad Campbell <lists2009@...rfbargle.com> > > >Cc: Maxim Levitsky <mlevitsk@...hat.com> > > >Cc: Paolo Bonzini <pbonzini@...hat.com> > > >Cc: kvm@...r.kernel.org > > > > Should it have the following tag since it fixes a commit introduced in 5.6? > > Cc: stable@...r.kernel.org # v5.6 > > It definitely warrants a backport to v5.6. I didn't include a Cc to stable > because I swear I had seen an email fly by that stated an explicit Cc is > unnecessary/unwanted for tip-tree patches, but per a recent statement from > Boris it looks like I'm simply confused[*]. I'll add the Cc in v2. > > [*] https://lkml.kernel.org/r/20200417164752.GF7322@zn.tnic Yeah, I was simply parroting what Greg has told me. Maybe he should finally do that script. :-P Also, I believe Sasha's Skynet machine already does that... CCed both. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette
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