linux-kernel - Re: [PATCH v5 5/5] x86/kvm: Avoid dynamic allocation of pvclock data when SEV is active

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Message-ID: <20180906190342.GH11144@zn.tnic>
Date:   Thu, 6 Sep 2018 21:03:42 +0200
From:   Borislav Petkov <bp@...e.de>
To:     Sean Christopherson <sean.j.christopherson@...el.com>,
        Brijesh Singh <brijesh.singh@....com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        Tom Lendacky <thomas.lendacky@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>
Subject: Re: [PATCH v5 5/5] x86/kvm: Avoid dynamic allocation of pvclock data
 when SEV is active

On Thu, Sep 06, 2018 at 11:45:03AM -0700, Sean Christopherson wrote:
> Yep, though because the 4k chunk in __decrypted is @hv_clock_boot 
> that's used for cpus 0-127, __decrypted_XXX would effectively be:
> 
>    (((num_possible_cpus() * 32) / 4k) - 1) pages

Ok, sounds like a nice compromise to me.

Also, I wonder if using subsections would be even better when adding
other things to the decrypted section. I.e.,

.data..decrypted:

...

.data..decrypted.aux:

...

.data..decrypted.something_else:

and this way keep it still conceptually together by keeping the section
namespace clean because we're putting it all under .decrypted's
namespace.

Hmmm.

-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
--