Date:   Mon, 20 Mar 2023 17:49:50 +0100
From:   Peter Zijlstra <peterz@infradead.org>
To:     Lai Jiangshan <jiangshanlai@gmail.com>
Cc:     "H. Peter Anvin" <hpa@zytor.com>, Xin Li <xin3.li@intel.com>,
        linux-kernel@vger.kernel.org, x86@kernel.org, kvm@vger.kernel.org,
        tglx@linutronix.de, mingo@redhat.com, bp@alien8.de,
        dave.hansen@linux.intel.com, andrew.cooper3@citrix.com,
        seanjc@google.com, pbonzini@redhat.com, ravi.v.shankar@intel.com
Subject: Re: [PATCH v5 22/34] x86/fred: FRED initialization code
Message-ID: <20230320164950.GR2194297@hirez.programming.kicks-ass.net>
References: <20230307023946.14516-1-xin3.li@intel.com>
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On Sat, Mar 18, 2023 at 02:33:30PM +0800, Lai Jiangshan wrote:
> 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.