linux-kernel - Re: [PATCH] x86/sev-es: Do not use copy_from_kernel

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Message-ID: <baf98f4e-0d3a-ac6f-040f-7e578525c7f7@intel.com>
Date:   Thu, 7 Sep 2023 15:45:01 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Adam Dunlap <acdunlap@...gle.com>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        David Hildenbrand <david@...hat.com>,
        Mike Rapoport <rppt@...nel.org>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Nikunj A Dadhania <nikunj@....com>,
        Dionna Glaze <dionnaglaze@...gle.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Joerg Roedel <jroedel@...e.de>, Jacob Xu <jacobhxu@...gle.com>
Subject: Re: [PATCH] x86/sev-es: Do not use copy_from_kernel_nofault in early
 #VC handler

On 9/7/23 15:30, Adam Dunlap wrote:
>> In any case, the most straightforward way out of this mess is to
>> just move boot_cpu_data out of .bss and explicitly initialize it
>> along with some documentation explaining the situation.
> That seems totally reasonable. I tried applying the two patches that 
> you sent plus boot_cpu_data.x86_virt_bits = 0; in early_setup_idt(),

Let's just initialize boot_cpu_data to zero and get it out of .bss entirely.

> and that fixes the problems that we can see. Do you want me to send
> out a new patch with these changes together?
Well, ideally broken out in a couple of patches, but yeah, please resend
also with some revised changelogs based on what you've learned.