linux-kernel - Re: [PATCH 35/62] x86/sev-es: Setup per-cpu GHCBs for the runtime handler

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Date:   Wed, 12 Feb 2020 16:16:13 +0100
From:   Joerg Roedel <joro@...tes.org>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     X86 ML <x86@...nel.org>, "H. Peter Anvin" <hpa@...or.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Hellstrom <thellstrom@...are.com>,
        Jiri Slaby <jslaby@...e.cz>,
        Dan Williams <dan.j.williams@...el.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Juergen Gross <jgross@...e.com>,
        Kees Cook <keescook@...omium.org>,
        LKML <linux-kernel@...r.kernel.org>,
        kvm list <kvm@...r.kernel.org>,
        Linux Virtualization <virtualization@...ts.linux-foundation.org>,
        Joerg Roedel <jroedel@...e.de>
Subject: Re: [PATCH 35/62] x86/sev-es: Setup per-cpu GHCBs for the runtime
 handler

On Tue, Feb 11, 2020 at 02:46:11PM -0800, Andy Lutomirski wrote:
> On Tue, Feb 11, 2020 at 5:53 AM Joerg Roedel <joro@...tes.org> wrote:
> > +/* Runtime GHCBs */
> > +static DEFINE_PER_CPU_DECRYPTED(struct ghcb, ghcb_page) __aligned(PAGE_SIZE);
> 
> Hmm.  This is a largeish amount of memory on large non-SEV-ES systems.
> Maybe store a pointer instead?  It would be even better if it could be
> DEFINE_PER_CPU like this but be discarded if we don't need it, but I
> don't think we have the infrastructure for that.

Yeah, discarding is not easily possible right now, but I changed it to
only store a pointer and allocating the pages only when running as an
SEV-ES guest.

Regards,

	Joerg