linux-kernel - Re: [PATCH v6 5/5] x86/kvm: Avoid dynamic allocation of pvclock data when SEV is active

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Message-ID: <20180911102504.GC11418@zn.tnic>
Date:   Tue, 11 Sep 2018 12:25:04 +0200
From:   Borislav Petkov <bp@...e.de>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Brijesh Singh <brijesh.singh@....com>,
        Sean Christopherson <sean.j.christopherson@...el.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>,
        Radim Krčmář <rkrcmar@...hat.com>
Subject: Re: [PATCH v6 5/5] x86/kvm: Avoid dynamic allocation of pvclock data
 when SEV is active

On Tue, Sep 11, 2018 at 12:19:13PM +0200, Paolo Bonzini wrote:
> That's exactly what kvmclock is for, it provides a stable and
> synchronized clock on top of unsynchronized TSCs.  But that's also why
> you need one struct per vCPU, at least in the synchronized case.

Why?

Why can't it be a single pointer to a struct pvclock_vsyscall_time_info
shared between all vCPUs?

Or does each vCPU write its own specific stuff into it so it has to be
per-vCPU?

-- 
Regards/Gruss,
    Boris.

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