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: <efde397b-35fc-c47b-b21e-898fa2ec6920@amd.com>
Date:   Fri, 29 Jul 2022 14:22:18 -0500
From:   Tom Lendacky <thomas.lendacky@....com>
To:     Dave Hansen <dave.hansen@...el.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 14:08, Dave Hansen wrote:
> 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?

Is s/memory acceptance/page state changes/ enough of what you are looking 
for or something more?

Thanks,
Tom