linux-kernel - RE: [PATCH v5 22/34] x86/fred: FRED initialization code

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Date:   Tue, 21 Mar 2023 00:12:06 +0000
From:   "Li, Xin3" <xin3.li@...el.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Lai Jiangshan <jiangshanlai@...il.com>
CC:     "H. Peter Anvin" <hpa@...or.com>,
        "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>,
        "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 22/34] x86/fred: FRED initialization code

> > If there is no other concrete reason other than overflowing for
> > assigning NMI and #DB with a stack level > 0, #VE should also be
> > assigned with a stack level > 0, and #BP too. #VE can happen anytime
> > and anywhere, so it is subject to overflowing too.
> 
> So #BP needs the stack-gap (redzone) for text_poke_bp().
> 
> #BP can end up in kprobes which can then end up in ftrace/perf, depending on
> how it's all wired up.
> 
> #VE is currently a trainwreck vs NMI/MCE, but I think FRED solves the worst of
> that. I'm not exactly sure how deep the #VE handler goes.
> 

VE under IDT is *not* using an IST, we need some solid rationales here.

Thanks!
  Xin