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

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Message-ID: <20190514070941.GE2589@hirez.programming.kicks-ass.net>
Date:   Tue, 14 May 2019 09:09:41 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     Alexandre Chartre <alexandre.chartre@...cle.com>,
        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>,
        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 11:18:41AM -0700, Andy Lutomirski wrote:
> 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.

I'm thinking the per-cpu random pool is a secrit. IOW, it demonstrably
does contain secrits, invalidating that premise.