From: Sohil Mehta <sohil.mehta@intel.com>
To: "Chen, Yian" <yian.chen@intel.com>,
<linux-kernel@vger.kernel.org>, <x86@kernel.org>,
Andy Lutomirski <luto@kernel.org>,
Dave Hansen <dave.hansen@linux.intel.com>,
Ravi Shankar <ravi.v.shankar@intel.com>,
"Tony Luck" <tony.luck@intel.com>,
Paul Lai <paul.c.lai@intel.com>
Subject: Re: [PATCH 4/7] x86/vsyscall: Setup vsyscall to compromise LASS protection
Date: Wed, 11 Jan 2023 18:49:39 -0800 [thread overview]
Message-ID: <de08c24f-782d-69e5-6547-6efe0c4ca94a@intel.com> (raw)
In-Reply-To: <adf3a609-656f-82a2-6a4e-199a12de298b@intel.com>
>> The existing documentation here is incorrect. The default vsyscall
>> mode is actually xonly. This has been so since:
>> commit 625b7b7f79c6 (x86/vsyscall: Change the default vsyscall mode to
>> xonly)
>>
> Yes, you are right. but this patch can overwrite and correct existing
> one. I am assuming we don't need to correct the existing document first
> before update it for LASS.
>
We should fix this independent of the LASS enabling. I sent a patch
earlier today to address it. I apologize, I missed cc'ing you.
https://lore.kernel.org/lkml/20230111193211.1987047-1-sohil.mehta@intel.com/
>>> + In newer versions of Intel platforms that come with
>>
>> Words such as "newer" in the kernel start losing meaning very quickly.
>> Also, this comment looks out of place in between the vsyscall
>> sub-options.
>>
>>> + LASS(Linear Address Space separation) protection,
>>> + vsyscall is disabled by default. Enabling vsyscall
>>> + via the parameter overrides LASS protection.
>>> +
> Sure, I will take out this part change.
Actually, having some text here might be ok. I mistook it to be placed
between the sub-options. But avoid merging it with the previous
paragraph as is the case right now.
>> Instead of doing this dance, can we provide a simplified behavior to
>> the user/admin and move the decision making to compile time?
>>
> Current strategy is to disable vsyscall by default only for LASS capable
> platforms. So that the dynamic decision is likely a necessary.
>
Making this dynamic and platform dependent would make things hard to
debug and isolate. It would be a perfect recipe for "But, it works on my
system!" type of issues.
Let's see what others have to say.
-Sohil
next prev parent reply other threads:[~2023-01-12 2:49 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-10 5:51 [PATCH 0/7] Enable LASS (Linear Address space Separation) Yian Chen
2023-01-10 5:51 ` [PATCH 1/7] x86/cpu: Enumerate LASS CPUID and CR4 bits Yian Chen
2023-01-10 20:14 ` Sohil Mehta
2023-01-11 0:13 ` Dave Hansen
2023-01-11 23:23 ` Chen, Yian
2023-01-12 0:06 ` Luck, Tony
2023-01-12 0:15 ` Chen, Yian
2023-01-11 19:21 ` Chen, Yian
2023-01-10 5:51 ` [PATCH 2/7] x86: Add CONFIG option X86_LASS Yian Chen
2023-01-10 21:05 ` Sohil Mehta
2023-01-12 0:13 ` Chen, Yian
2023-01-10 5:52 ` [PATCH 3/7] x86/cpu: Disable kernel LASS when patching kernel alternatives Yian Chen
2023-01-10 21:04 ` Peter Zijlstra
2023-01-11 1:01 ` Chen, Yian
2023-01-11 9:10 ` Peter Zijlstra
2023-01-10 22:41 ` Sohil Mehta
2023-01-12 0:27 ` Chen, Yian
2023-01-12 0:37 ` Dave Hansen
2023-01-12 18:36 ` Chen, Yian
2023-01-12 18:48 ` Dave Hansen
2023-02-01 2:25 ` Sohil Mehta
2023-02-01 18:20 ` Dave Hansen
2023-02-01 2:10 ` Sohil Mehta
2023-01-10 5:52 ` [PATCH 4/7] x86/vsyscall: Setup vsyscall to compromise LASS protection Yian Chen
2023-01-11 0:34 ` Sohil Mehta
2023-01-12 1:43 ` Chen, Yian
2023-01-12 2:49 ` Sohil Mehta [this message]
2023-01-21 4:09 ` Andy Lutomirski
2023-01-10 5:52 ` [PATCH 5/7] x86/cpu: Enable LASS (Linear Address Space Separation) Yian Chen
2023-01-11 22:22 ` Sohil Mehta
2023-01-12 17:56 ` Chen, Yian
2023-01-12 18:17 ` Dave Hansen
2023-01-13 1:17 ` Sohil Mehta
2023-01-13 19:39 ` Sohil Mehta
2023-01-10 5:52 ` [PATCH 6/7] x86/cpu: Set LASS as pinning sensitive CR4 bit Yian Chen
2023-01-10 5:52 ` [PATCH 7/7] x86/kvm: Expose LASS feature to VM guest Yian Chen
2023-02-07 3:21 ` Wang, Lei
2023-02-09 17:18 ` Sean Christopherson
2023-01-10 19:48 ` [PATCH 0/7] Enable LASS (Linear Address space Separation) Sohil Mehta
2023-01-10 22:57 ` Dave Hansen
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