linux-kernel - Re: [PATCH v4 51/75] x86/sev-es: Handle MMIO events

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Date:   Thu, 23 Jul 2020 09:21:02 +0200
From:   Joerg Roedel <joro@...tes.org>
To:     Mike Stunes <mstunes@...are.com>
Cc:     Joerg Roedel <jroedel@...e.de>, "x86@...nel.org" <x86@...nel.org>,
        Tom Lendacky <thomas.lendacky@....com>,
        "hpa@...or.com" <hpa@...or.com>, Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Jiri Slaby <jslaby@...e.cz>,
        Dan Williams <dan.j.williams@...el.com>,
        Juergen Gross <jgross@...e.com>,
        Kees Cook <keescook@...omium.org>,
        David Rientjes <rientjes@...gle.com>,
        Cfir Cohen <cfir@...gle.com>,
        Erdem Aktas <erdemaktas@...gle.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Martin Radev <martin.b.radev@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "virtualization@...ts.linux-foundation.org" 
        <virtualization@...ts.linux-foundation.org>
Subject: Re: [PATCH v4 51/75] x86/sev-es: Handle MMIO events

Hi Mike,

On Wed, Jul 22, 2020 at 10:53:02PM +0000, Mike Stunes wrote:
> Thanks Joerg! With that change in place, this kernel boots normally.
> What was the problem?

The problem was that the code got its page-table from
current->active_mm. But these pointers are not set up during early boot,
so that the #VC handler can't walk the page-table and propagates a
page-fault every time. This loops forever.

Getting the page-table from CR3 instead works at all stages of the
systems runtime.

Regards,

	Joerg