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Date:   Mon, 18 Jul 2022 17:19:13 -0700
From:   Joao Moreira <joao@overdrivepizza.com>
To:     Linus Torvalds <torvalds@linux-foundation.org>
Cc:     Thomas Gleixner <tglx@linutronix.de>,
        Sami Tolvanen <samitolvanen@google.com>,
        Peter Zijlstra <peterz@infradead.org>,
        LKML <linux-kernel@vger.kernel.org>,
        the arch/x86 maintainers <x86@kernel.org>,
        Tim Chen <tim.c.chen@linux.intel.com>,
        Josh Poimboeuf <jpoimboe@kernel.org>,
        "Cooper, Andrew" <andrew.cooper3@citrix.com>,
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        "Moreira, Joao" <joao.moreira@intel.com>,
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        "Gross, Jurgen" <jgross@suse.com>,
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        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Peter Collingbourne <pcc@google.com>
Subject: Re: [patch 00/38] x86/retbleed: Call depth tracking mitigation
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> The extra instruction is likely less of a problem than the extra 
> register used.
> 
FWIIW, per-ABI, R11 is a scratch-reg and should be usable without hard 
consequences in this scenario.

Joao