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From:   Adam Dunlap <acdunlap@google.com>
Date:   Mon, 2 Oct 2023 14:46:25 -0700
Message-ID: <CAMBK9=ayzz3yz-Cbf3vx1=v2bFqQM8Vmyo0NtfoKY0jqGuBk_g@mail.gmail.com>
Subject: Re: [PATCH v2 2/2] x86/sev-es: Only set x86_virt_bits to correct value
To:     Dave Hansen <dave.hansen@intel.com>
Cc:     Nathan Chancellor <nathan@kernel.org>,
        linux-kernel@vger.kernel.org, x86@kernel.org,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Andy Lutomirski <luto@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Sean Christopherson <seanjc@google.com>,
        Kim Phillips <kim.phillips@amd.com>,
        Juergen Gross <jgross@suse.com>,
        Ashok Raj <ashok.raj@intel.com>,
        Joerg Roedel <jroedel@suse.de>,
        Tom Lendacky <thomas.lendacky@amd.com>,
        David Hildenbrand <david@redhat.com>,
        Mike Rapoport <rppt@kernel.org>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Nikunj A Dadhania <nikunj@amd.com>,
        Dionna Glaze <dionnaglaze@google.com>,
        Peter Gonda <pgonda@google.com>,
        David Rientjes <rientjes@google.com>,
        Khalid ElMously <khalid.elmously@canonical.com>,
        Jacob Xu <jacobhxu@google.com>, llvm@lists.linux.dev
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On Mon, Oct 2, 2023 at 2:41=E2=80=AFPM Dave Hansen <dave.hansen@intel.com> =
wrote:
>
> On 10/2/23 13:04, Nathan Chancellor wrote:
> > On Mon, Sep 11, 2023 at 05:27:03PM -0700, Adam Dunlap wrote:
> >> Instead of setting x86_virt_bits to a possibly-correct value and then
> >> correcting it later, do all the necessary checks before setting it.
> >>
> >> At this point, the #VC handler references boot_cpu_data.x86_virt_bits,
> >> and in the previous version, it would be triggered by the cpuids betwe=
en
> >> the point at which it is set to 48 and when it is set to the correct
> >> value.
> >>
> >> Suggested-by: Dave Hansen <dave.hansen@linux.intel.com>
> >> Signed-off-by: Adam Dunlap <acdunlap@google.com>
> > Our continuous integration started seeing panics when booting ARCH=3Di3=
86
> > without KVM after this change landed in -tip as commit fbf6449f84bf
> > ("x86/sev-es: Set x86_virt_bits to the correct value straight away,
> > instead of a two-phase approach"):
>
> I can't reproduce this, but I'm running a gcc-built kernel and I haven't
> tried very hard to replicate your qemu setup.
>
> I did notice, though, that the patch in question forgot to move one
> assignment.  Could you see if the attached patch fixes things for you?

I reproduced the issue as Nathan described and your attached patch fixes it
for me.