linux-kernel - Re: [PATCH RFC V2 17/17] x86/entry: Preserve PKRS MSR across exceptions

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Message-ID: <1cdb358b-861a-5f74-8cd0-84ee5265035c@intel.com>
Date:   Thu, 23 Jul 2020 09:23:13 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Fenghua Yu <fenghua.yu@...el.com>,
        Andy Lutomirski <luto@...nel.org>
Cc:     Weiny Ira <ira.weiny@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        X86 ML <x86@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Vishal Verma <vishal.l.verma@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-nvdimm <linux-nvdimm@...ts.01.org>,
        Linux FS Devel <linux-fsdevel@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>
Subject: Re: [PATCH RFC V2 17/17] x86/entry: Preserve PKRS MSR across
 exceptions

On 7/23/20 9:18 AM, Fenghua Yu wrote:
> The PKRS MSR has been preserved in thread_info during kernel entry. We
> don't need to preserve it in another place (i.e. idtentry_state).

I'm missing how the PKRS MSR gets preserved in thread_info.  Could you
explain the mechanism by which this happens and point to the code
implementing it, please?