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

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Date:   Thu, 6 Sep 2018 17:19:38 +0200
From:   Borislav Petkov <bp@...e.de>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     Brijesh Singh <brijesh.singh@....com>, 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 07:56:40AM -0700, Sean Christopherson wrote:
> Wouldn't that result in @hv_clock_boot being incorrectly freed in the
> !SEV case?

Ok, maybe I'm missing something but why do we need 4K per CPU? Why can't
we map all those pages which contain the clock variable, decrypted in
all guests' page tables?

Basically

(NR_CPUS * sizeof(struct pvclock_vsyscall_time_info)) / 4096

pages.

For the !SEV case then nothing changes.

-- 
Regards/Gruss,
    Boris.

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