linux-kernel - Re: [PATCH v4 00/75] x86: SEV-ES Guest Support

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Date:   Wed, 22 Jul 2020 11:04:42 +0200
From:   Joerg Roedel <jroedel@...e.de>
To:     Erdem Aktas <erdemaktas@...gle.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Joerg Roedel <joro@...tes.org>, x86@...nel.org, hpa@...or.com,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.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>,
        David Rientjes <rientjes@...gle.com>,
        Cfir Cohen <cfir@...gle.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mike Stunes <mstunes@...are.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Martin Radev <martin.b.radev@...il.com>,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH v4 00/75] x86: SEV-ES Guest Support

Hi Erdem,

On Tue, Jul 21, 2020 at 09:48:51AM -0700, Erdem Aktas wrote:
> Yes, I am using OVMF with SEV-ES (sev-es-v12 patches applied). I am
> running Ubuntu 18.04 distro. My grub target is x86_64-efi. I also
> tried installing the grub-efi-amd64 package. In all cases, the grub is
> running in 64bit but enters the startup_32 in 32 bit mode. I think
> there should be a 32bit #VC handler just something very similar in the
> OVMF patches to handle the cpuid when the CPU is still in 32bit mode.
> As it is now, it will be a huge problem to support different distro images.
> I wonder if I am the only one having this problem.

I havn't heard from anyone else that the startup_32 boot-path is being
used for SEV-ES. What OVMF binary do you use for your guest?

In general it is not that difficult to support that boot-path too, but
I'd like to keep that as a future addition, as the patch-set is already
quite large. In the startup_32 path there is already a GDT set up, so
whats needed is an IDT and a 32-bit #VC handler using the MRS-based
protocol (and hoping that there will only be CPUID intercepts until it
reaches long-mode).

Regards,

	Joerg