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: <70a5c939-16a6-d5e0-2e38-ac7adbed5fc1@intel.com>
Date:   Fri, 29 Jul 2022 12:28:45 -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 12:22, Tom Lendacky wrote:
>> 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?
> 
> Is s/memory acceptance/page state changes/ enough of what you are
> looking for or something more?

That, plus a reminder of when "page state changes" are performed would
be nice.  How frequent are they?  Are they performance sensitive?
That'll help us decide if the design here is appropriate or not.