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

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Date:   Mon, 10 Sep 2018 11:14:10 -0500
From:   Brijesh Singh <brijesh.singh@....com>
To:     Borislav Petkov <bp@...e.de>
Cc:     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>,
        Sean Christopherson <sean.j.christopherson@...el.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 09/10/2018 10:53 AM, Borislav Petkov wrote:
> On Mon, Sep 10, 2018 at 08:15:38AM -0500, Brijesh Singh wrote:
>>> Now, the real question from all this SNAFU is, why can't all those point
>>> to a single struct pvclock_vsyscall_time_info and all CPUs read a single
>>> thing? Why do they have to be per-CPU and thus waste so much memory?
> 
> You forgot to answer to the real question - why do we need those things
> to be perCPU and why can't we use a single instance to share with *all*
> CPUs?
> 
> Because if we can, then we're golden!
> 


I did not forgot to answer it. Maybe Paolo or someone more knowledgeable
in that area of code can comment why those are perCpu.

-Brijesh