linux-kernel - Re: [RFC KVM 18/27] kvm/isolation: function to copy page table entries for percpu buffer

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Date:   Mon, 13 May 2019 11:18:41 -0700
From:   Andy Lutomirski <luto@...nel.org>
To:     Alexandre Chartre <alexandre.chartre@...cle.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krcmar <rkrcmar@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andrew Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        kvm list <kvm@...r.kernel.org>, X86 ML <x86@...nel.org>,
        Linux-MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        jan.setjeeilers@...cle.com, Liran Alon <liran.alon@...cle.com>,
        Jonathan Adams <jwadams@...gle.com>
Subject: Re: [RFC KVM 18/27] kvm/isolation: function to copy page table
 entries for percpu buffer

On Mon, May 13, 2019 at 7:39 AM Alexandre Chartre
<alexandre.chartre@...cle.com> wrote:
>
> pcpu_base_addr is already mapped to the KVM address space, but this
> represents the first percpu chunk. To access a per-cpu buffer not
> allocated in the first chunk, add a function which maps all cpu
> buffers corresponding to that per-cpu buffer.
>
> Also add function to clear page table entries for a percpu buffer.
>

This needs some kind of clarification so that readers can tell whether
you're trying to map all percpu memory or just map a specific
variable.  In either case, you're making a dubious assumption that
percpu memory contains no secrets.