linux-kernel - Re: [PATCH 00/54] KVM: x86/mmu: Bug fixes and summer cleaning

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Date:   Wed, 23 Jun 2021 21:06:50 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Yu Zhang <yu.c.zhang@...ux.intel.com>,
        Maxim Levitsky <mlevitsk@...hat.com>
Subject: Re: [PATCH 00/54] KVM: x86/mmu: Bug fixes and summer cleaning

On Wed, Jun 23, 2021, Paolo Bonzini wrote:
> On 22/06/21 19:56, Sean Christopherson wrote:
> > Patch 01 is the only patch that is remotely 5.13 worthy, and even then
> > only because it's about as safe as a patch can be.  Everything else is far
> > from urgent as these bugs have existed for quite some time.
> 
> Maybe patch 54 (not sarcastic), but I agree it's not at all necessary.
> 
> This is good stuff, I made a few comments but almost all of them (all except
> the last comment on patch 9, "Unconditionally zap unsync SPs") are cosmetic
> and I can resolve them myself.

The 0-day bot also reported some warnings.  vcpu_to_role_regs() needs to be
static, the helpers are added without a user.  I liked the idea of adding the
helpers in one patch, but I can't really defend adding them without a user. :-/

   arch/x86/kvm/mmu/mmu.c:209:26: warning: no previous prototype for function 'vcpu_to_role_regs' [-Wmissing-prototypes]
   struct kvm_mmu_role_regs vcpu_to_role_regs(struct kvm_vcpu *vcpu)
                            ^
   arch/x86/kvm/mmu/mmu.c:209:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
   struct kvm_mmu_role_regs vcpu_to_role_regs(struct kvm_vcpu *vcpu)
   ^
   static
   arch/x86/kvm/mmu/mmu.c:199:1: warning: unused function '____is_cr0_wp' [-Wunused-function]
   BUILD_MMU_ROLE_REGS_ACCESSOR(cr0, wp, X86_CR0_WP);

> 
> I'd like your input on renaming is_{cr0,cr4,efer}_* to is_mmu_* (and
> possibly reduce the four underscores to two...).
> 
> If I get remarks by tomorrow, I'll get this into 5.14, otherwise consider
> everything but the first eight patches queued only for 5.15.
> 
> > I labeled the "sections" of this mess in the shortlog below.
> > 
> > P.S. Does anyone know how PKRU interacts with NPT?  I assume/hope NPT
> >       accesses, which are always "user", ignore PKRU, but the APM doesn't
> >       say a thing.  If PKRU is ignored, KVM has some fixing to do.  If PKRU
> >       isn't ignored, AMD has some fixing to do:-)
> > 
> > P.S.S. This series pulled in one patch from my vCPU RESET/INIT series,
> >         "Properly reset MMU context at vCPU RESET/INIT", as that was needed
> >         to fix a root_level bug on VMX.  My goal is to get the RESET/INIT
> >         series refreshed later this week and thoroughly bombard everyone.
> 
> Note that it won't get into 5.14 anyway, since I plan to send my first pull
> request to Linus as soon as Friday.

Good to know.  I'll still try to get it out tomorrow as I'll be on vacation
for a few weeks starting Friday, and I'm afraid I'll completely forget what's in
the series :-)