Messages in this thread | | | Date | Thu, 12 Jan 2023 17:17:53 -0800 | Subject | Re: [PATCH 5/7] x86/cpu: Enable LASS (Linear Address Space Separation) | From | Sohil Mehta <> |
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On 1/12/2023 10:17 AM, Dave Hansen wrote:
> In the end, want X86_CR4_LASS set when the kernel wants LASS and clear > in *ALL* other cases. That would be simply: > > if (cpu_feature_enabled(X86_FEATURE_LASS)) { > cr4_set_bits(X86_CR4_LASS); > } else { > cr4_clear_bits(X86_CR4_LASS); > } >
Thanks for the explanation. This is very helpful.
> I'm also wondering if we even want a Kconfig option. Is anyone > realistically going to be compiling this support out?
I was initially thinking we should leave the Kconfig option for users that really *need* vsyscall support. But, thinking about it more, we don't need an LASS Kconfig option for that.
We can make CONFIG_LEGACY_VSYSCALL_NONE as the default instead of the current CONFIG_LEGACY_VSYSCALL_XONLY. The kernel can disable LASS at boot time if a user/admin has shown explicit preference by selecting CONFIG_LEGACY_VSYSCALL_XONLY or by providing command line parameter vsyscall=xonly/emulate.
Thoughts?
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