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

Kirill A. Shutemov
2021-09-22T14:32:11Z

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