linux-kernel - RE: [RFC PATCH 14/32] x86/fred: header file with FRED definitions

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Message-ID: <BN6PR1101MB21615569318BD964A2855F44A8EB9@BN6PR1101MB2161.namprd11.prod.outlook.com>
Date:   Wed, 21 Dec 2022 02:58:06 +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: [RFC PATCH 14/32] x86/fred: header file with FRED definitions

> > +/*
> > + * FRED return instructions
> > + *
> > + * Replace with "ERETS"/"ERETU" once binutils support FRED return
> instructions.
> 
> binutils version that supports these instructions goes here...
> 
> > + */
> > +#define ERETS			_ASM_BYTES(0xf2,0x0f,0x01,0xca)
> > +#define ERETU			_ASM_BYTES(0xf3,0x0f,0x01,0xca)
> > +
> > +/*
> > + * Event stack level macro for the FRED_STKLVLS MSR.
> > + * Usage example: FRED_STKLVL(X86_TRAP_DF, 3)
> > + * Multiple values can be ORd together.
> > + */
> > +#define FRED_STKLVL(v,l)	(_AT(unsigned long, l) << (2*(v)))
> > +
> > +/* FRED_CONFIG MSR */
> > +#define FRED_CONFIG_CSL_MASK		0x3
> > +#define FRED_CONFIG_SHADOW_STACK_SPACE	_BITUL(3)
> > +#define FRED_CONFIG_REDZONE(b)		__ALIGN_KERNEL_MASK((b),
> _UL(0x3f))
> > +#define FRED_CONFIG_INT_STKLVL(l)	(_AT(unsigned long, l) << 9)
> > +#define FRED_CONFIG_ENTRYPOINT(p)	_AT(unsigned long, (p))
> > +
> > +/* FRED event type and vector bit width and counts */
> > +#define FRED_EVENT_TYPE_BITS		3 /* only 3 bits used in FRED 3.0
> */
> > +#define FRED_EVENT_TYPE_COUNT		_BITUL(FRED_EVENT_TYPE_BITS)
> > +#define FRED_EVENT_VECTOR_BITS		8
> > +#define FRED_EVENT_VECTOR_COUNT
> 	_BITUL(FRED_EVENT_VECTOR_BITS)
> > +
> > +/* FRED EVENT_TYPE_OTHER vector numbers */
> > +#define FRED_SYSCALL			1
> > +#define FRED_SYSENTER			2
> > +
> > +/* Flags above the CS selector (regs->csl) */
> > +#define FRED_CSL_ENABLE_NMI		_BITUL(28)
> > +#define FRED_CSL_ALLOW_SINGLE_STEP	_BITUL(25)
> > +#define FRED_CSL_INTERRUPT_SHADOW	_BITUL(24)
> 
> What's the state of IBT WAIT-FOR-ENDBR vs this? That really should also get a
> high CS bit.

FRED does provide more possibilities :)