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From: Jarkko Sakkinen <jarkko@kernel.org>
To: Reinette Chatre <reinette.chatre@intel.com>
Cc: dave.hansen@linux.intel.com, tglx@linutronix.de, bp@alien8.de,
	luto@kernel.org, mingo@redhat.com, linux-sgx@vger.kernel.org,
	x86@kernel.org, seanjc@google.com, kai.huang@intel.com,
	cathy.zhang@intel.com, cedric.xing@intel.com,
	haitao.huang@intel.com, mark.shanahan@intel.com, hpa@zytor.com,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 05/25] x86/sgx: Introduce runtime protection bits
Date: Sun, 5 Dec 2021 00:50:59 +0200	[thread overview]
Message-ID: <Yavw05Op0PTm3AuX@iki.fi> (raw)
In-Reply-To: <2f6b04dd8949591ee6139072c72eb93da3dd07b0.1638381245.git.reinette.chatre@intel.com>

What about:

"x86/sgx: Add encl_page->vm_run_prot_bits for dynamic permission changes"

On Wed, Dec 01, 2021 at 11:23:03AM -0800, Reinette Chatre wrote:
> Enclave creators declare their paging permission intent at the time
> the pages are added to the enclave. These paging permissions are
> vetted when pages are added to the enclave and stashed off
> (in sgx_encl_page->vm_max_prot_bits) for later comparison with
> enclave PTEs.
> 
> Current permission support assume that enclave page permissions
> remain static for the lifetime of the enclave. This is about to change
> with the addition of support for SGX2 where the permissions of enclave
> pages belonging to an initialized enclave may be changed during the
> enclave's lifetime.
> 
> Introduce runtime protection bits in preparation for support of

By writing "Introduce runtime protection bits", instead of simply "Add
encl_page->vm_run_prot_bits", the only thing you are adding is obfuscation.

Try to refer to the "exact thing", instead of English rephrasing
whenever possible.

> enclave page permission changes. These bits reflect the active
> permissions of an enclave page and are not to exceed the maximum
> protection bits that passed scrutiny during enclave creation.
> 
> Associate runtime protection bits with each enclave page. Initialize
> the runtime protection bits to the vetted maximum protection bits
> on page creation. Use the runtime protection bits for any access
> checks.

I guess the first sentence in this paragraph is completely redundant
as the first sentence of the previous paragraph tells the exact
same story.

> struct sgx_encl_page hosting this information is maintained for each
> enclave page so the space consumed by the struct is important.
> The existing vm_max_prot_bits is already unsigned long while only using
> three bits. Transition to a bitfield for the two members containing
> protection bits.
> 
> Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>

So this commit message left the most important thing unanswered,
or I missed it (which happens quite often): why two fields instead
of one? Why vm_max_port_bits needs to stay constant?

It's something that should be clearly documented.

/Jarkko

  parent reply	other threads:[~2021-12-04 22:51 UTC|newest]

Thread overview: 155+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-12-01 19:22 [PATCH 00/25] x86/sgx and selftests/sgx: Support SGX2 Reinette Chatre
2021-12-01 19:22 ` [PATCH 01/25] x86/sgx: Add shortlog descriptions to ENCLS wrappers Reinette Chatre
2021-12-04 18:30   ` Jarkko Sakkinen
2021-12-06 21:13     ` Reinette Chatre
2021-12-11  5:28       ` Jarkko Sakkinen
2021-12-13 22:06         ` Reinette Chatre
2021-12-01 19:23 ` [PATCH 02/25] x86/sgx: Add wrappers for SGX2 functions Reinette Chatre
2021-12-04 22:04   ` Jarkko Sakkinen
2021-12-06 21:15     ` Reinette Chatre
2021-12-01 19:23 ` [PATCH 03/25] x86/sgx: Support VMA permissions exceeding enclave permissions Reinette Chatre
2021-12-04 22:25   ` Jarkko Sakkinen
2021-12-04 22:27     ` Jarkko Sakkinen
2021-12-06 21:16       ` Reinette Chatre
2021-12-11  5:39         ` Jarkko Sakkinen
2021-12-13 22:08           ` Reinette Chatre
2021-12-01 19:23 ` [PATCH 04/25] x86/sgx: Add pfn_mkwrite() handler for present PTEs Reinette Chatre
2021-12-04 22:43   ` Jarkko Sakkinen
2021-12-06 21:18     ` Reinette Chatre
2021-12-11  7:37       ` Jarkko Sakkinen
2021-12-13 22:09         ` Reinette Chatre
2021-12-28 14:51           ` Jarkko Sakkinen
2021-12-01 19:23 ` [PATCH 05/25] x86/sgx: Introduce runtime protection bits Reinette Chatre
2021-12-03 19:28   ` Andy Lutomirski
2021-12-03 22:12     ` Reinette Chatre
2021-12-04  0:38       ` Andy Lutomirski
2021-12-04  1:14         ` Reinette Chatre
2021-12-04 17:56           ` Andy Lutomirski
2021-12-04 23:55             ` Reinette Chatre
2021-12-13 22:34               ` Reinette Chatre
2021-12-04 23:57     ` Jarkko Sakkinen
2021-12-06 21:20       ` Reinette Chatre
2021-12-11  7:42         ` Jarkko Sakkinen
2021-12-13 22:10           ` Reinette Chatre
2021-12-28 14:52             ` Jarkko Sakkinen
2022-01-06 17:46               ` Reinette Chatre
2022-01-07 12:16                 ` Jarkko Sakkinen
2022-01-07 16:14                   ` Haitao Huang
2022-01-08 15:45                     ` Jarkko Sakkinen
2022-01-08 15:51                       ` Jarkko Sakkinen
2022-01-08 16:22                         ` Jarkko Sakkinen
2022-01-10 22:05                           ` Haitao Huang
2022-01-11  1:53                             ` Jarkko Sakkinen
2022-01-11  1:55                               ` Jarkko Sakkinen
2022-01-11  2:03                                 ` Jarkko Sakkinen
2022-01-11  2:15                                   ` Jarkko Sakkinen
2022-01-11  3:48                                     ` Haitao Huang
2022-01-12 23:48                                       ` Jarkko Sakkinen
2022-01-13  2:41                                         ` Haitao Huang
2022-01-14 21:36                                           ` Jarkko Sakkinen
2022-01-11 17:13                               ` Reinette Chatre
2022-01-12 23:50                                 ` Jarkko Sakkinen
2022-01-12 23:56                                   ` Jarkko Sakkinen
2022-01-13 20:09                                     ` Nathaniel McCallum
2022-01-13 21:42                                       ` Reinette Chatre
2022-01-14 21:53                                         ` Jarkko Sakkinen
2022-01-14 21:57                                           ` Jarkko Sakkinen
2022-01-14 22:00                                             ` Jarkko Sakkinen
2022-01-14 22:17                                           ` Jarkko Sakkinen
2022-01-14 22:23                                             ` Jarkko Sakkinen
2022-01-14 22:34                                               ` Jarkko Sakkinen
2022-01-14 23:05                                           ` Reinette Chatre
2022-01-14 23:15                                             ` Jarkko Sakkinen
2022-01-15  0:01                                               ` Reinette Chatre
2022-01-15  0:27                                                 ` Jarkko Sakkinen
2022-01-15  0:41                                                   ` Reinette Chatre
2022-01-15  1:18                                                     ` Jarkko Sakkinen
2022-01-15 11:56                                                       ` Jarkko Sakkinen
2022-01-15 11:59                                                         ` Jarkko Sakkinen
2022-01-17 13:13                                                         ` Nathaniel McCallum
2022-01-18  1:59                                                           ` Jarkko Sakkinen
2022-01-18  2:22                                                             ` Jarkko Sakkinen
2022-01-18  3:31                                                               ` Jarkko Sakkinen
2022-01-18 20:59                                                               ` Reinette Chatre
2022-01-20 12:53                                                                 ` Jarkko Sakkinen
2022-01-20 16:52                                                                   ` Reinette Chatre
2022-01-26 14:41                                                                     ` Jarkko Sakkinen
2022-01-15 16:49                                               ` Jarkko Sakkinen
2022-01-18 21:18                                                 ` Reinette Chatre
2022-01-17 13:27                                         ` Nathaniel McCallum
2022-01-18 21:11                                           ` Reinette Chatre
2021-12-04 22:50   ` Jarkko Sakkinen [this message]
2021-12-06 21:28     ` Reinette Chatre
2021-12-01 19:23 ` [PATCH 06/25] x86/sgx: Use more generic name for enclave cpumask function Reinette Chatre
2021-12-04 22:56   ` Jarkko Sakkinen
2021-12-06 21:29     ` Reinette Chatre
2021-12-01 19:23 ` [PATCH 07/25] x86/sgx: Move PTE zap code to separate function Reinette Chatre
2021-12-04 22:59   ` Jarkko Sakkinen
2021-12-06 21:30     ` Reinette Chatre
2021-12-11  7:52       ` Jarkko Sakkinen
2021-12-13 22:11         ` Reinette Chatre
2021-12-28 14:55           ` Jarkko Sakkinen
2022-01-06 17:46             ` Reinette Chatre
2022-01-07 12:26               ` Jarkko Sakkinen
2021-12-01 19:23 ` [PATCH 08/25] x86/sgx: Make SGX IPI callback available internally Reinette Chatre
2021-12-04 23:00   ` Jarkko Sakkinen
2021-12-06 21:36     ` Reinette Chatre
2021-12-11  7:53       ` Jarkko Sakkinen
2021-12-01 19:23 ` [PATCH 09/25] x86/sgx: Keep record of SGX page type Reinette Chatre
2021-12-04 23:03   ` Jarkko Sakkinen
2021-12-01 19:23 ` [PATCH 10/25] x86/sgx: Support enclave page permission changes Reinette Chatre
2021-12-02 23:48   ` Dave Hansen
2021-12-03 18:18     ` Reinette Chatre
2021-12-03  0:32   ` Dave Hansen
2021-12-03 18:18     ` Reinette Chatre
2021-12-03 18:14   ` Dave Hansen
2021-12-03 18:49     ` Reinette Chatre
2021-12-03 19:38   ` Andy Lutomirski
2021-12-03 22:34     ` Reinette Chatre
2021-12-04  0:42       ` Andy Lutomirski
2021-12-04  1:35         ` Reinette Chatre
2021-12-04 23:08   ` Jarkko Sakkinen
2021-12-06 20:19     ` Dave Hansen
2021-12-11  5:17       ` Jarkko Sakkinen
2021-12-06 21:42     ` Reinette Chatre
2021-12-11  7:57       ` Jarkko Sakkinen
2021-12-13 22:12         ` Reinette Chatre
2021-12-28 14:56           ` Jarkko Sakkinen
2021-12-01 19:23 ` [PATCH 11/25] selftests/sgx: Add test for EPCM " Reinette Chatre
2021-12-01 19:23 ` [PATCH 12/25] selftests/sgx: Add test for TCS page " Reinette Chatre
2021-12-01 19:23 ` [PATCH 13/25] x86/sgx: Support adding of pages to initialized enclave Reinette Chatre
2021-12-03  0:38   ` Dave Hansen
2021-12-03 18:47     ` Reinette Chatre
2021-12-04 23:13   ` Jarkko Sakkinen
2021-12-06 21:44     ` Reinette Chatre
2021-12-11  8:00       ` Jarkko Sakkinen
2021-12-13 22:12         ` Reinette Chatre
2021-12-28 14:57           ` Jarkko Sakkinen
2022-03-01 15:13   ` Jarkko Sakkinen
2022-03-01 17:08     ` Reinette Chatre
2021-12-01 19:23 ` [PATCH 14/25] x86/sgx: Tighten accessible memory range after enclave initialization Reinette Chatre
2021-12-04 23:14   ` Jarkko Sakkinen
2021-12-06 21:45     ` Reinette Chatre
2021-12-11  8:01       ` Jarkko Sakkinen
2021-12-01 19:23 ` [PATCH 15/25] selftests/sgx: Test two different SGX2 EAUG flows Reinette Chatre
2021-12-01 19:23 ` [PATCH 16/25] x86/sgx: Support modifying SGX page type Reinette Chatre
2021-12-04 23:45   ` Jarkko Sakkinen
2021-12-06 21:48     ` Reinette Chatre
2021-12-11  8:02       ` Jarkko Sakkinen
2021-12-13 17:43         ` Dave Hansen
2021-12-21  8:52           ` Jarkko Sakkinen
2021-12-01 19:23 ` [PATCH 17/25] x86/sgx: Support complete page removal Reinette Chatre
2021-12-04 23:45   ` Jarkko Sakkinen
2021-12-06 21:49     ` Reinette Chatre
2021-12-01 19:23 ` [PATCH 18/25] selftests/sgx: Introduce dynamic entry point Reinette Chatre
2021-12-01 19:23 ` [PATCH 19/25] selftests/sgx: Introduce TCS initialization enclave operation Reinette Chatre
2021-12-01 19:23 ` [PATCH 20/25] selftests/sgx: Test complete changing of page type flow Reinette Chatre
2021-12-01 19:23 ` [PATCH 21/25] selftests/sgx: Test faulty enclave behavior Reinette Chatre
2021-12-01 19:23 ` [PATCH 22/25] selftests/sgx: Test invalid access to removed enclave page Reinette Chatre
2021-12-01 19:23 ` [PATCH 23/25] selftests/sgx: Test reclaiming of untouched page Reinette Chatre
2021-12-01 19:23 ` [PATCH 24/25] x86/sgx: Free up EPC pages directly to support large page ranges Reinette Chatre
2021-12-04 23:47   ` Jarkko Sakkinen
2021-12-06 22:07     ` Reinette Chatre
2021-12-01 19:23 ` [PATCH 25/25] selftests/sgx: Page removal stress test Reinette Chatre
2021-12-02 18:30 ` [PATCH 00/25] x86/sgx and selftests/sgx: Support SGX2 Dave Hansen
2021-12-02 20:38   ` Nathaniel McCallum

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