From: Thomas Gleixner <tglx@linutronix.de>
To: Borislav Petkov <bp@alien8.de>
Cc: Kuppuswamy Sathyanarayanan
<sathyanarayanan.kuppuswamy@linux.intel.com>,
Ingo Molnar <mingo@redhat.com>,
x86@kernel.org, Paolo Bonzini <pbonzini@redhat.com>,
David Hildenbrand <david@redhat.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Juergen Gross <jgross@suse.com>, Deep Shah <sdeep@vmware.com>,
VMware Inc <pv-drivers@vmware.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
Peter H Anvin <hpa@zytor.com>,
Dave Hansen <dave.hansen@intel.com>,
Tony Luck <tony.luck@intel.com>,
Dan Williams <dan.j.williams@intel.com>,
Andi Kleen <ak@linux.intel.com>,
Kirill Shutemov <kirill.shutemov@linux.intel.com>,
Sean Christopherson <seanjc@google.com>,
Kuppuswamy Sathyanarayanan <knsathya@kernel.org>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v10 03/11] x86/cpufeatures: Add TDX Guest CPU feature
Date: Wed, 13 Oct 2021 23:25:35 +0200 [thread overview]
Message-ID: <877deg8vn4.ffs@tglx> (raw)
In-Reply-To: <YWdKlG0AzmjpjJKW@zn.tnic>
On Wed, Oct 13 2021 at 23:07, Borislav Petkov wrote:
> On Wed, Oct 13, 2021 at 10:44:37PM +0200, Thomas Gleixner wrote:
>> No. This is tasteless garbage, really.
>>
>> tdx_early_init() is invoked from x86_64_start_kernel() very early in the
>> boot process __before__ is_tdx_guest() is invoked.
>>
>> So why on earth is it requried to keep those conditionals and cpuid()
>> muck around after init?
>
> Yah, reportedly, they wanna parse cmdline options so it has to be after
> copy_bootdata() but copy_bootdata() has a cc_platform_has() call which
> ends up in is_tdx_guest() on Intel and there you have the catch 22
> because CPUID hasn't happened yet in tdx_early_init().
Seriously?
So this ends up in doing:
use();
init();
Can you spot what's wrong with that?
That's a clear violation of common sense and is simply not going to
happen. Why? If you think about deep defensive programming then use()
will look like this:
use()
{
assert(initialized);
}
which is not something made up. It's a fundamental principle of
programming and some languages enforce that for very good reasons.
Just because it can be done in C is no justification.
What's wrong with:
x86_64_start_kernel()
tdx_early_init();
copy_bootdata();
tdx_late_init();
Absolutely nothing. It's clear, simple and well defined.
Thanks,
tglx
next prev parent reply other threads:[~2021-10-13 21:25 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-09 5:37 [PATCH v10 00/11] Add TDX Guest Support (Initial support) Kuppuswamy Sathyanarayanan
2021-10-09 5:37 ` [PATCH v10 01/11] x86/paravirt: Move halt paravirt calls under CONFIG_PARAVIRT Kuppuswamy Sathyanarayanan
2021-10-15 16:59 ` David Hildenbrand
2021-10-09 5:37 ` [PATCH v10 02/11] x86/tdx: Introduce INTEL_TDX_GUEST config option Kuppuswamy Sathyanarayanan
2021-10-11 18:19 ` Josh Poimboeuf
2021-10-11 18:38 ` Andi Kleen
2021-10-11 18:47 ` Kuppuswamy, Sathyanarayanan
2021-10-09 5:37 ` [PATCH v10 03/11] x86/cpufeatures: Add TDX Guest CPU feature Kuppuswamy Sathyanarayanan
2021-10-13 8:18 ` Borislav Petkov
2021-10-13 13:32 ` Sathyanarayanan Kuppuswamy
2021-10-13 19:42 ` Josh Poimboeuf
2021-10-13 23:19 ` Thomas Gleixner
2021-10-14 0:25 ` Josh Poimboeuf
2021-10-14 7:57 ` Borislav Petkov
[not found] ` <1a6220a5-3abd-dea1-4b2f-2acade311236@linux.intel.com>
2021-10-18 21:59 ` Borislav Petkov
2021-10-18 22:04 ` Sathyanarayanan Kuppuswamy
2021-10-13 20:44 ` Thomas Gleixner
2021-10-13 21:05 ` Sathyanarayanan Kuppuswamy
2021-10-13 21:35 ` Thomas Gleixner
2021-10-13 21:07 ` Borislav Petkov
2021-10-13 21:25 ` Thomas Gleixner [this message]
2021-10-13 21:37 ` Borislav Petkov
2021-10-13 22:28 ` Sathyanarayanan Kuppuswamy
2021-10-13 23:02 ` Thomas Gleixner
2021-10-14 17:28 ` Sathyanarayanan Kuppuswamy
2021-10-09 5:37 ` [PATCH v10 04/11] x86/tdx: Add TDX support to intel_cc_platform_has() Kuppuswamy Sathyanarayanan
2021-10-13 15:57 ` Borislav Petkov
2021-10-14 7:12 ` Thomas Gleixner
2021-10-14 17:31 ` Sathyanarayanan Kuppuswamy
2021-10-09 5:37 ` [PATCH v10 05/11] x86/tdx: Add __tdx_module_call() and __tdx_hypercall() helper functions Kuppuswamy Sathyanarayanan
2021-10-14 7:28 ` Thomas Gleixner
2021-10-15 0:19 ` Sathyanarayanan Kuppuswamy
2021-10-09 5:37 ` [PATCH v10 06/11] x86/traps: Add #VE support for TDX guest Kuppuswamy Sathyanarayanan
2021-10-14 8:30 ` Thomas Gleixner
2021-10-17 2:45 ` Sathyanarayanan Kuppuswamy
2021-10-17 3:18 ` Dave Hansen
2021-10-17 3:49 ` Sathyanarayanan Kuppuswamy
2021-10-09 5:37 ` [PATCH v10 07/11] x86/tdx: Add HLT " Kuppuswamy Sathyanarayanan
2021-10-14 9:30 ` Thomas Gleixner
2021-10-15 1:33 ` Sathyanarayanan Kuppuswamy
2021-10-15 15:03 ` Sean Christopherson
2021-10-09 5:37 ` [PATCH v10 08/11] x86/tdx: Wire up KVM hypercalls Kuppuswamy Sathyanarayanan
2021-10-14 10:21 ` Thomas Gleixner
2021-10-15 3:03 ` Sathyanarayanan Kuppuswamy
2021-10-09 5:37 ` [PATCH v10 09/11] x86/tdx: Add MSR support for TDX guest Kuppuswamy Sathyanarayanan
2021-10-09 5:37 ` [PATCH v10 10/11] x86/tdx: Don't write CSTAR MSR on Intel Kuppuswamy Sathyanarayanan
2021-10-14 10:47 ` Thomas Gleixner
2021-10-14 13:47 ` Andi Kleen
2021-10-14 14:27 ` Thomas Gleixner
2021-10-09 5:37 ` [PATCH v10 11/11] x86/tdx: Handle CPUID via #VE Kuppuswamy Sathyanarayanan
2021-10-14 12:01 ` Thomas Gleixner
2021-10-14 13:25 ` Dave Hansen
2021-10-09 7:38 ` [PATCH v10 00/11] Add TDX Guest Support (Initial support) Borislav Petkov
2021-10-09 20:56 ` Kuppuswamy, Sathyanarayanan
2021-10-11 13:03 ` Borislav Petkov
2021-10-11 16:33 ` Dave Hansen
2021-10-11 16:48 ` Dave Hansen
2021-10-11 17:04 ` Borislav Petkov
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