Re: [PATCH v3 5/8] x86/sme: Replace occurrences of sme_active() with cc_platform_has()

From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Borislav Petkov <bp@alien8.de>,
	linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org,
	linux-kernel@vger.kernel.org, x86@kernel.org,
	iommu@lists.linux-foundation.org, kvm@vger.kernel.org,
	linux-efi@vger.kernel.org, platform-driver-x86@vger.kernel.org,
	linux-graphics-maintainer@vmware.com,
	amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org,
	kexec@lists.infradead.org, linux-fsdevel@vger.kernel.org,
	Brijesh Singh <brijesh.singh@amd.com>,
	Joerg Roedel <joro@8bytes.org>, Andi Kleen <ak@linux.intel.com>,
	Sathyanarayanan Kuppuswamy 
	<sathyanarayanan.kuppuswamy@linux.intel.com>,
	Tianyu Lan <Tianyu.Lan@microsoft.com>,
	Christoph Hellwig <hch@infradead.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Andy Lutomirski <luto@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Will Deacon <will@kernel.org>
Subject: Re: [PATCH v3 5/8] x86/sme: Replace occurrences of sme_active() with cc_platform_has()
Date: Wed, 22 Sep 2021 17:30:15 +0300	[thread overview]
Message-ID: <20210922143015.vvxvh6ec73lffvkf@box.shutemov.name> (raw)
In-Reply-To: <01891f59-7ec3-cf62-a8fc-79f79ca76587@amd.com>

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