linux-kernel - Re: [PATCH v3 5/8] x86/sme: Replace occurrences of sme_active() with cc_platform

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Date:   Wed, 22 Sep 2021 17:30:15 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Tom Lendacky <thomas.lendacky@....com>
Cc:     Borislav Petkov <bp@...en8.de>, linuxppc-dev@...ts.ozlabs.org,
        linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        x86@...nel.org, iommu@...ts.linux-foundation.org,
        kvm@...r.kernel.org, linux-efi@...r.kernel.org,
        platform-driver-x86@...r.kernel.org,
        linux-graphics-maintainer@...are.com,
        amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        kexec@...ts.infradead.org, linux-fsdevel@...r.kernel.org,
        Brijesh Singh <brijesh.singh@....com>,
        Joerg Roedel <joro@...tes.org>,
        Andi Kleen <ak@...ux.intel.com>,
        Sathyanarayanan Kuppuswamy 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        Tianyu Lan <Tianyu.Lan@...rosoft.com>,
        Christoph Hellwig <hch@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Will Deacon <will@...nel.org>
Subject: Re: [PATCH v3 5/8] x86/sme: Replace occurrences of sme_active() with
 cc_platform_has()

On Wed, Sep 22, 2021 at 08:40:43AM -0500, Tom Lendacky wrote:
> On 9/21/21 4:58 PM, Kirill A. Shutemov wrote:
> > On Tue, Sep 21, 2021 at 04:43:59PM -0500, Tom Lendacky wrote:
> > > On 9/21/21 4:34 PM, Kirill A. Shutemov wrote:
> > > > On Tue, Sep 21, 2021 at 11:27:17PM +0200, Borislav Petkov wrote:
> > > > > On Wed, Sep 22, 2021 at 12:20:59AM +0300, Kirill A. Shutemov wrote:
> > > > > > I still believe calling cc_platform_has() from __startup_64() is totally
> > > > > > broken as it lacks proper wrapping while accessing global variables.
> > > > > 
> > > > > Well, one of the issues on the AMD side was using boot_cpu_data too
> > > > > early and the Intel side uses it too. Can you replace those checks with
> > > > > is_tdx_guest() or whatever was the helper's name which would check
> > > > > whether the the kernel is running as a TDX guest, and see if that helps?
> > > > 
> > > > There's no need in Intel check this early. Only AMD need it. Maybe just
> > > > opencode them?
> > > 
> > > Any way you can put a gzipped/bzipped copy of your vmlinux file somewhere I
> > > can grab it from and take a look at it?
> > 
> > You can find broken vmlinux and bzImage here:
> > 
> > https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdrive.google.com%2Fdrive%2Ffolders%2F1n74vUQHOGebnF70Im32qLFY8iS3wvjIs%3Fusp%3Dsharing&amp;data=04%7C01%7Cthomas.lendacky%40amd.com%7C1c7adf380cbe4c1a6bb708d97d4af6ff%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637678583935705530%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&amp;sdata=gA30x%2Bfu97tUx0p2UqI8HgjiL8bxDbK1GqgJBbUrUE4%3D&amp;reserved=0
> > 
> > Let me know when I can remove it.
> 
> Looking at everything, it is all RIP relative addressing, so those
> accesses should be fine.

Not fine, but waiting to blowup with random build environment change.

> Your image has the intel_cc_platform_has()
> function, does it work if you remove that call? Because I think it may be
> the early call into that function which looks like it has instrumentation
> that uses %gs in __sanitizer_cov_trace_pc and %gs is not setup properly
> yet. And since boot_cpu_data.x86_vendor will likely be zero this early it
> will match X86_VENDOR_INTEL and call into that function.

Right removing call to intel_cc_platform_has() or moving it to
cc_platform.c fixes the issue.

-- 
 Kirill A. Shutemov