linux-kernel - RE: [PATCH v5 25/34] x86/fred: disallow the swapgs instruction when FRED is enabled

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Message-ID: <SA1PR11MB6734297C9F3B758D27B7765BA8809@SA1PR11MB6734.namprd11.prod.outlook.com>
Date:   Mon, 20 Mar 2023 17:58:14 +0000
From:   "Li, Xin3" <xin3.li@...el.com>
To:     Peter Zijlstra <peterz@...radead.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "bp@...en8.de" <bp@...en8.de>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "hpa@...or.com" <hpa@...or.com>,
        "andrew.cooper3@...rix.com" <andrew.cooper3@...rix.com>,
        "Christopherson,, Sean" <seanjc@...gle.com>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "Shankar, Ravi V" <ravi.v.shankar@...el.com>
Subject: RE: [PATCH v5 25/34] x86/fred: disallow the swapgs instruction when
 FRED is enabled

> > The FRED architecture establishes the full supervisor/user through:
> > 1) FRED event delivery swaps the value of the GS base address and
> >    that of the IA32_KERNEL_GS_BASE MSR.
> > 2) ERETU swaps the value of the GS base address and that of the
> >    IA32_KERNEL_GS_BASE MSR.
> > Thus, the swapgs instruction is disallowed when FRED is enabled,
> > otherwise it cauess #UD.
>                  ^^^ --- new word :-)

My stupid fingers...