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

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Date:   Wed, 22 Jul 2020 09:54:40 -0700
From:   Erdem Aktas <erdemaktas@...gle.com>
To:     Joerg Roedel <jroedel@...e.de>
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

I am using a custom, optimized and stripped down version, OVMF build.
Do you think it is because of the OVMF or grub?

In my case, there are 2 places where the CPUID is called: the first
one is to decide if long mode is supported, along with few other
features like SSE support and the second one is to retrieve the
encryption bit location.

-Erdem

On Wed, Jul 22, 2020 at 2:04 AM Joerg Roedel <jroedel@...e.de> wrote:
>
> 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
>