From: Sohil Mehta <sohil.mehta@intel.com>
To: "Edgecombe, Rick P" <rick.p.edgecombe@intel.com>,
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Subject: Re: [PATCH v10 04/15] x86/cpu: Set LASS CR4 bit as pinning sensitive
Date: Fri, 10 Oct 2025 12:03:24 -0700 [thread overview]
Message-ID: <2dfba3fa-64f8-494f-a4da-46934f21d10d@intel.com> (raw)
In-Reply-To: <66212761b9ef76b209e83e08c9258b76f51dbebc.camel@intel.com>
On 10/8/2025 9:52 AM, Edgecombe, Rick P wrote:
> And unlike the other bits that just got added easily, this
> one required infrastructure changes and extra patch. So wondered, hmm, is it
> worth it to do the extra patches?
>
Yeah, I reconsidered its usefulness as well.
Though, adding it to CR4 pinned mask is a net positive, even with the
extra patch. As part of the pinning enforcement, we get the warning if
LASS is turned off by accident. The bit gets reprogrammed automatically
which, even if not useful, wouldn't harm in any way.
Also, the changes to defer CR pinning enforcement seem to be useful
independent of LASS. Plus, the patch turned out to be simpler than I had
imagined.
> Yea, I agree it would be good to get a warning. The write may be triggered
> accidentally by a kernel bug. I agree with the patch, but just commenting my
> reasoning for the sake of discussion. Maybe we can tighten the reasoning in the
> log.
Will do.
next prev parent reply other threads:[~2025-10-10 19:03 UTC|newest]
Thread overview: 74+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-10-07 6:51 [PATCH v10 00/15] x86: Enable Linear Address Space Separation support Sohil Mehta
2025-10-07 6:51 ` [PATCH v10 01/15] x86/cpu: Enumerate the LASS feature bits Sohil Mehta
2025-10-07 18:19 ` Edgecombe, Rick P
2025-10-07 18:28 ` Dave Hansen
2025-10-07 20:20 ` Sohil Mehta
2025-10-07 20:38 ` Edgecombe, Rick P
2025-10-07 20:53 ` Sohil Mehta
2025-10-16 3:10 ` H. Peter Anvin
2025-10-07 20:49 ` Sohil Mehta
2025-10-07 23:16 ` Xin Li
2025-10-08 16:00 ` Edgecombe, Rick P
2025-10-16 15:35 ` Borislav Petkov
2025-10-21 18:03 ` Sohil Mehta
2025-10-07 6:51 ` [PATCH v10 02/15] x86/asm: Introduce inline memcpy and memset Sohil Mehta
2025-10-21 12:47 ` Borislav Petkov
2025-10-21 13:48 ` David Laight
2025-10-21 18:06 ` Sohil Mehta
2025-10-07 6:51 ` [PATCH v10 03/15] x86/alternatives: Disable LASS when patching kernel alternatives Sohil Mehta
2025-10-07 16:55 ` Edgecombe, Rick P
2025-10-07 22:28 ` Sohil Mehta
2025-10-08 16:22 ` Edgecombe, Rick P
2025-10-10 17:10 ` Sohil Mehta
2025-10-21 20:03 ` Borislav Petkov
2025-10-21 20:55 ` Sohil Mehta
2025-10-22 9:56 ` Borislav Petkov
2025-10-22 19:49 ` Sohil Mehta
2025-10-22 20:03 ` Luck, Tony
2025-10-22 8:25 ` Peter Zijlstra
2025-10-22 9:40 ` Borislav Petkov
2025-10-22 10:22 ` Peter Zijlstra
2025-10-22 10:52 ` Borislav Petkov
2025-10-07 6:51 ` [PATCH v10 04/15] x86/cpu: Set LASS CR4 bit as pinning sensitive Sohil Mehta
2025-10-07 18:24 ` Edgecombe, Rick P
2025-10-07 23:11 ` Sohil Mehta
2025-10-08 16:52 ` Edgecombe, Rick P
2025-10-10 19:03 ` Sohil Mehta [this message]
2025-10-07 6:51 ` [PATCH v10 05/15] x86/cpu: Defer CR pinning enforcement until late_initcall() Sohil Mehta
2025-10-07 17:23 ` Edgecombe, Rick P
2025-10-07 23:05 ` Sohil Mehta
2025-10-08 17:36 ` Edgecombe, Rick P
2025-10-10 20:45 ` Sohil Mehta
2025-10-15 21:17 ` Sohil Mehta
2025-10-17 19:28 ` Sohil Mehta
2025-10-07 6:51 ` [PATCH v10 06/15] x86/efi: Disable LASS while mapping the EFI runtime services Sohil Mehta
2025-10-07 6:51 ` [PATCH v10 07/15] x86/kexec: Disable LASS during relocate kernel Sohil Mehta
2025-10-07 17:43 ` Edgecombe, Rick P
2025-10-07 22:33 ` Sohil Mehta
2025-10-07 6:51 ` [PATCH v10 08/15] x86/vsyscall: Reorganize the page fault emulation code Sohil Mehta
2025-10-07 18:37 ` Edgecombe, Rick P
2025-10-07 18:48 ` Dave Hansen
2025-10-07 19:53 ` Edgecombe, Rick P
2025-10-07 22:52 ` Sohil Mehta
2025-10-08 17:42 ` Edgecombe, Rick P
2025-10-30 16:58 ` Andy Lutomirski
2025-10-30 17:22 ` H. Peter Anvin
2025-10-30 17:35 ` Andy Lutomirski
2025-10-30 19:28 ` Sohil Mehta
2025-10-30 21:37 ` David Laight
2025-10-07 6:51 ` [PATCH v10 09/15] x86/traps: Consolidate user fixups in exc_general_protection() Sohil Mehta
2025-10-07 17:46 ` Edgecombe, Rick P
2025-10-07 22:41 ` Sohil Mehta
2025-10-08 17:43 ` Edgecombe, Rick P
2025-10-07 6:51 ` [PATCH v10 10/15] x86/vsyscall: Add vsyscall emulation for #GP Sohil Mehta
2025-10-07 6:51 ` [PATCH v10 11/15] x86/vsyscall: Disable LASS if vsyscall mode is set to EMULATE Sohil Mehta
2025-10-07 18:43 ` Edgecombe, Rick P
2025-10-07 6:51 ` [PATCH v10 12/15] x86/traps: Communicate a LASS violation in #GP message Sohil Mehta
2025-10-07 18:07 ` Edgecombe, Rick P
2025-10-07 6:51 ` [PATCH v10 13/15] x86/traps: Generalize #GP address decode and hint code Sohil Mehta
2025-10-07 18:43 ` Edgecombe, Rick P
2025-10-07 6:51 ` [PATCH v10 14/15] x86/traps: Provide additional hints for a kernel stack segment fault Sohil Mehta
2025-10-07 6:51 ` [PATCH v10 15/15] x86/cpu: Enable LASS by default during CPU initialization Sohil Mehta
2025-10-07 18:42 ` Edgecombe, Rick P
2025-10-07 16:23 ` [PATCH v10 00/15] x86: Enable Linear Address Space Separation support Edgecombe, Rick P
2025-10-17 19:52 ` Sohil Mehta
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