From:   "Li, Xin3" <xin3.li@intel.com>
To:     Peter Zijlstra <peterz@infradead.org>,
        Lai Jiangshan <jiangshanlai@gmail.com>
CC:     "H. Peter Anvin" <hpa@zytor.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "x86@kernel.org" <x86@kernel.org>,
        "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
        "tglx@linutronix.de" <tglx@linutronix.de>,
        "mingo@redhat.com" <mingo@redhat.com>,
        "bp@alien8.de" <bp@alien8.de>,
        "dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>,
        "andrew.cooper3@citrix.com" <andrew.cooper3@citrix.com>,
        "Christopherson,, Sean" <seanjc@google.com>,
        "pbonzini@redhat.com" <pbonzini@redhat.com>,
        "Shankar, Ravi V" <ravi.v.shankar@intel.com>
Subject: RE: [PATCH v5 22/34] x86/fred: FRED initialization code
Thread-Topic: [PATCH v5 22/34] x86/fred: FRED initialization code
Thread-Index: AQHZUKIwUYB0dIbGLUidau1bSRiyL67/CYqAgACFIwCAAJcqAIAD0N0AgAB6oTA=
Date:   Tue, 21 Mar 2023 00:12:06 +0000
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> > 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.
>=20
> So #BP needs the stack-gap (redzone) for text_poke_bp().
>=20
> #BP can end up in kprobes which can then end up in ftrace/perf, depending=
 on
> how it's all wired up.
>=20
> #VE is currently a trainwreck vs NMI/MCE, but I think FRED solves the wor=
st of
> that. I'm not exactly sure how deep the #VE handler goes.
>=20

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

Thanks!
  Xin