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From: Dave Hansen <dave.hansen@intel.com>
To: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de,
	luto@kernel.org, peterz@infradead.org,
	sathyanarayanan.kuppuswamy@linux.intel.com, aarcange@redhat.com,
	ak@linux.intel.com, dan.j.williams@intel.com, david@redhat.com,
	hpa@zytor.com, jgross@suse.com, jmattson@google.com,
	joro@8bytes.org, jpoimboe@redhat.com, knsathya@kernel.org,
	pbonzini@redhat.com, sdeep@vmware.com, seanjc@google.com,
	tony.luck@intel.com, vkuznets@redhat.com, wanpengli@tencent.com,
	thomas.lendacky@amd.com, brijesh.singh@amd.com, x86@kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCHv4 17/30] x86/tdx: Add port I/O emulation
Date: Sun, 27 Feb 2022 20:32:38 -0800	[thread overview]
Message-ID: <b1ddd8eb-0165-7d31-e253-d69c3a8e7db9@intel.com> (raw)
In-Reply-To: <20220228011627.63355pcbpn7tosiy@black.fi.intel.com>

On 2/27/22 17:16, Kirill A. Shutemov wrote:
> Anyway, it is in our plans to sort it out, but it is not in scope of core
> enabling. Let's make it functional first.

Yeah, but we need to know what these plans are.  There's still a _bit_
too much hand-waving and "trust us" going on in this set.

If this can induce extra SIGSEV's in userspace that aren't possible in
non-TDX systems, please call that out.

For instance, something like this in the changelog of this patch would
be really nice:

	== Userspace Implications ==

	The ioperm() facility allows userspace access to I/O
	instructions like inb/outb.  Among other things, this allows
	writing userspace device drivers.

	This series has no special handling for ioperm().  Users
	will be able to successfully request I/O permissions but will
	induce a #VE on their first I/O instruction.  If this is
	undesirable users can <add advice here about LOCKDOWN_IOPORT>

	More robust handling of this situation (denying ioperm() in
	all TDX guests) will be addressed in follow-on work.

That says: This causes a problem.  The problem looks like this.  It can
be addressed now by doing $FOO or later by doing $BAR.

But, the *problem* needs to be called out.  That way, folks can actually
think about the problem rather than just reading a happy changelog that
neglects to mention any of the problems that the patch leaves in its wake.

The same goes for the CPUID mess.  I'm not demanding a full solution in
the patch or the series even.  But, what I am demanding is a full
_problem_ disclosure.

  reply	other threads:[~2022-02-28  4:32 UTC|newest]

Thread overview: 88+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-02-24 15:56 [PATCHv4 00/30] TDX Guest: TDX core support Kirill A. Shutemov
2022-02-24 15:56 ` [PATCHv4 01/30] x86/mm: Fix warning on build with X86_MEM_ENCRYPT=y Kirill A. Shutemov
2022-02-24 16:06   ` Dave Hansen
2022-02-27 22:01   ` Josh Poimboeuf
2022-02-28 16:20     ` Kirill A. Shutemov
2022-02-28 16:40       ` Josh Poimboeuf
2022-02-28 16:51         ` Dave Hansen
2022-02-28 17:11           ` Josh Poimboeuf
2022-03-01  8:48             ` Borislav Petkov
2022-02-24 15:56 ` [PATCHv4 02/30] x86/tdx: Detect running as a TDX guest in early boot Kirill A. Shutemov
2022-02-24 16:16   ` Dave Hansen
2022-02-24 15:56 ` [PATCHv4 03/30] x86/tdx: Provide common base for SEAMCALL and TDCALL C wrappers Kirill A. Shutemov
2022-02-24 16:35   ` Dave Hansen
2022-02-24 23:10     ` Kirill A. Shutemov
2022-02-25  0:41       ` Dave Hansen
2022-02-25 10:39         ` Kai Huang
2022-02-25 15:46         ` Kirill A. Shutemov
2022-02-25 16:12           ` Dave Hansen
2022-02-24 15:56 ` [PATCHv4 04/30] x86/tdx: Add __tdx_module_call() and __tdx_hypercall() helper functions Kirill A. Shutemov
2022-02-24 17:01   ` Dave Hansen
2022-02-24 23:29     ` Kirill A. Shutemov
2022-02-24 15:56 ` [PATCHv4 05/30] x86/tdx: Extend the confidential computing API to support TDX guests Kirill A. Shutemov
2022-02-24 17:54   ` Dave Hansen
2022-02-24 23:54     ` Kirill A. Shutemov
2022-02-25  0:51       ` Dave Hansen
2022-02-24 15:56 ` [PATCHv4 06/30] x86/tdx: Exclude shared bit from __PHYSICAL_MASK Kirill A. Shutemov
2022-02-24 15:56 ` [PATCHv4 07/30] x86/traps: Add #VE support for TDX guest Kirill A. Shutemov
2022-02-24 18:36   ` Dave Hansen
2022-02-25 19:30     ` Kirill A. Shutemov
2022-02-25 19:46       ` Dave Hansen
2022-02-24 15:56 ` [PATCHv4 08/30] x86/tdx: Add HLT support for TDX guests Kirill A. Shutemov
2022-02-24 18:42   ` Dave Hansen
2022-02-24 15:56 ` [PATCHv4 09/30] x86/tdx: Add MSR " Kirill A. Shutemov
2022-02-24 18:52   ` Dave Hansen
2022-02-24 19:04     ` Sean Christopherson
2022-02-24 19:36       ` Dave Hansen
2022-02-26 21:35     ` Kirill A. Shutemov
2022-02-24 15:56 ` [PATCHv4 10/30] x86/tdx: Handle CPUID via #VE Kirill A. Shutemov
2022-02-24 19:04   ` Dave Hansen
2022-02-27  1:07     ` Kirill A. Shutemov
2022-02-28 16:41       ` Dave Hansen
2022-02-28 22:53         ` Kirill A. Shutemov
2022-02-28 23:05           ` Dave Hansen
2022-02-28 23:31             ` Kirill A. Shutemov
2022-02-28 23:37               ` Dave Hansen
2022-02-24 15:56 ` [PATCHv4 11/30] x86/tdx: Handle in-kernel MMIO Kirill A. Shutemov
2022-02-24 20:11   ` Dave Hansen
2022-02-25  2:23     ` David Laight
2022-02-25  3:10       ` David Laight
2022-03-02 13:42     ` Kirill A. Shutemov
2022-02-24 15:56 ` [PATCHv4 12/30] x86/tdx: Detect TDX at early kernel decompression time Kirill A. Shutemov
2022-02-24 20:44   ` Dave Hansen
2022-02-24 15:56 ` [PATCHv4 13/30] x86: Adjust types used in port I/O helpers Kirill A. Shutemov
2022-02-24 21:24   ` Dave Hansen
2022-02-24 15:56 ` [PATCHv4 14/30] x86: Consolidate " Kirill A. Shutemov
2022-02-24 15:56 ` [PATCHv4 15/30] x86/boot: Allow to hook up alternative " Kirill A. Shutemov
2022-02-24 22:14   ` Dave Hansen
2022-02-27 22:02   ` Josh Poimboeuf
2022-02-28 16:33     ` Kirill A. Shutemov
2022-02-28 16:44       ` Josh Poimboeuf
2022-02-24 15:56 ` [PATCHv4 16/30] x86/boot/compressed: Support TDX guest port I/O at decompression time Kirill A. Shutemov
2022-02-24 22:22   ` Dave Hansen
2022-02-24 15:56 ` [PATCHv4 17/30] x86/tdx: Add port I/O emulation Kirill A. Shutemov
2022-02-24 22:43   ` Dave Hansen
2022-02-25  3:59   ` Dave Hansen
2022-02-28  1:16     ` Kirill A. Shutemov
2022-02-28  4:32       ` Dave Hansen [this message]
2022-02-24 15:56 ` [PATCHv4 18/30] x86/tdx: Handle early boot port I/O Kirill A. Shutemov
2022-02-24 22:58   ` Dave Hansen
2022-02-24 15:56 ` [PATCHv4 19/30] x86/tdx: Wire up KVM hypercalls Kirill A. Shutemov
2022-02-24 15:56 ` [PATCHv4 20/30] x86/boot: Add a trampoline for booting APs via firmware handoff Kirill A. Shutemov
2022-02-24 15:56 ` [PATCHv4 21/30] x86/acpi, x86/boot: Add multiprocessor wake-up support Kirill A. Shutemov
2022-02-24 15:56 ` [PATCHv4 22/30] x86/boot: Set CR0.NE early and keep it set during the boot Kirill A. Shutemov
2022-02-24 15:56 ` [PATCHv4 23/30] x86/boot: Avoid #VE during boot for TDX platforms Kirill A. Shutemov
2022-02-24 15:56 ` [PATCHv4 24/30] x86/topology: Disable CPU online/offline control for TDX guests Kirill A. Shutemov
2022-02-24 15:56 ` [PATCHv4 25/30] x86/tdx: Make pages shared in ioremap() Kirill A. Shutemov
2022-02-24 15:56 ` [PATCHv4 26/30] x86/mm/cpa: Add support for TDX shared memory Kirill A. Shutemov
2022-02-24 15:56 ` [PATCHv4 27/30] x86/kvm: Use bounce buffers for TD guest Kirill A. Shutemov
2022-02-24 15:56 ` [PATCHv4 28/30] x86/tdx: ioapic: Add shared bit for IOAPIC base address Kirill A. Shutemov
2022-02-24 15:56 ` [PATCHv4 29/30] ACPICA: Avoid cache flush on TDX guest Kirill A. Shutemov
2022-02-27 22:05   ` Josh Poimboeuf
2022-02-28  1:34     ` Dan Williams
2022-02-28 16:37       ` Kirill A. Shutemov
2022-02-28 16:46         ` Dave Hansen
2022-02-28 17:02         ` Josh Poimboeuf
2022-02-24 15:56 ` [PATCHv4 30/30] Documentation/x86: Document TDX kernel architecture Kirill A. Shutemov
2022-02-25 17:42   ` Dave Hansen
2022-02-25 17:54   ` Dave Hansen

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