linux-kernel - Re: [PATCH v6 0/5] x86: Enable LKGS instruction

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <Y7/5YPxbRE2AWgT0@gmail.com>
Date:   Thu, 12 Jan 2023 13:13:20 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     Xin Li <xin3.li@...el.com>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com,
        hpa@...or.com, peterz@...radead.org, brgerst@...il.com,
        chang.seok.bae@...el.com, jgross@...e.com
Subject: Re: [PATCH v6 0/5] x86: Enable LKGS instruction


* Xin Li <xin3.li@...el.com> wrote:

> LKGS instruction is introduced with Intel FRED (flexible return and event 
> delivery) specification. As LKGS is independent of FRED, we enable it as 
> a standalone CPU feature.
> 
> LKGS behaves like the MOV to GS instruction except that it loads the base 
> address into the IA32_KERNEL_GS_BASE MSR instead of the GS segment’s 
> descriptor cache, which is exactly what Linux kernel does to load user 
> level GS base.  Thus, with LKGS, there is no need to SWAPGS away from the 
> kernel GS base.

Ok, this looks good to me.

I've applied the first 4 patches to tip:x86/cpu, as the instruction exists 
in a public document and these patches are fine stand-alone as well, such 
as the factoring out of load_gs_index() methods from a high-use low level 
header into a new header file.

Planning to apply the final, LKGS enabler patch as well, unless there's any 
objections from others?

Thanks,

	Ingo