linux-kernel - Re: [PATCH v3 03/13] KVM: x86: emulator: introduce emulator_recalc_and_set

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Date:   Fri, 12 Aug 2022 09:25:04 +0300
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     "Yang, Weijiang" <weijiang.yang@...el.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>
Cc:     Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Wanpeng Li <wanpengli@...cent.com>,
        Ingo Molnar <mingo@...hat.com>,
        "Christopherson,, Sean" <seanjc@...gle.com>,
        "x86@...nel.org" <x86@...nel.org>,
        Jim Mattson <jmattson@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>, Joerg Roedel <joro@...tes.org>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: Re: [PATCH v3 03/13] KVM: x86: emulator: introduce
 emulator_recalc_and_set_mode

On Thu, 2022-08-11 at 23:33 +0800, Yang, Weijiang wrote:
> On 8/3/2022 11:50 PM, Maxim Levitsky wrote:
> > [...]
> > +static inline int emulator_recalc_and_set_mode(struct x86_emulate_ctxt *ctxt)
> > +{
> > +       u64 efer;
> > +       struct desc_struct cs;
> > +       u16 selector;
> > +       u32 base3;
> > +
> > +       ctxt->ops->get_msr(ctxt, MSR_EFER, &efer);
> > +
> > +       if (!ctxt->ops->get_cr(ctxt, 0) & X86_CR0_PE) {

Ouch, thanks for catching this!!

I wonder how I didn't catch this in unit tests....
(I'll check on this Sunday)


Best regards,
	Maxim Levitsky

> Shouldn't this be:  !(ctxt->ops->get_cr(ctxt, 0) & X86_CR0_PE) ?
> > +               /* Real mode. cpu must not have long mode active */
> > +               if (efer & EFER_LMA)
> > +                       return X86EMUL_UNHANDLEABLE;
> > +               ctxt->mode = X86EMUL_MODE_REAL;
> > +               return X86EMUL_CONTINUE;
> > +       }
> > +
> [...]
> > --
> > 2.26.3
> >