linux-kernel - Re: [PATCH v1 1/2] x86/sev: Use per-CPU PSC structure in prep for unaccepted memory support

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Message-ID: <377f6c30-bdfc-55a4-bda7-f29c60c53300@intel.com>
Date:   Fri, 29 Jul 2022 12:08:38 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Tom Lendacky <thomas.lendacky@....com>,
        linux-kernel@...r.kernel.org, x86@...nel.org
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "Kirill A. Shutemov" <kirill@...temov.name>,
        "H. Peter Anvin" <hpa@...or.com>,
        Michael Roth <michael.roth@....com>,
        Joerg Roedel <jroedel@...e.de>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v1 1/2] x86/sev: Use per-CPU PSC structure in prep for
 unaccepted memory support

On 7/29/22 07:25, Tom Lendacky wrote:
>> Considering that runtime acceptance is already single-threaded[1] *and*
>> there's a fallback method, why not just have a single copy of this
>> guarded by a single lock?
> 
> This function is called for more than just memory acceptance. It's also
> called for any changes from or to private or shared, which isn't
> single-threaded.

I think this tidbit from the changelog threw me off:

> Protect the use of the per-CPU structure by disabling interrupts during
> memory acceptance.

Could you please revise that to accurately capture the impact of this
change?