linux-kernel - Re: [PATCH v1 1/2] selftests/x86/ldt

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Message-ID: <f67a6fd3-7dd4-4fbc-8936-4e7a5ac86696@intel.com>
Date: Fri, 23 Jan 2026 09:07:28 -0800
From: Dave Hansen <dave.hansen@...el.com>
To: Borislav Petkov <bp@...en8.de>, Slawomir Rosek <srosek@...gle.com>
Cc: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
 Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
 "H . Peter Anvin" <hpa@...or.com>, Shuah Khan <shuah@...nel.org>,
 Betty Zhou <bettyzhou@...gle.com>, Wake Liu <wakel@...gle.com>,
 Kazuhiro Inaba <kinaba@...gle.com>, Jeff Xu <jeffxu@...gle.com>,
 Alistair Delva <adelva@...gle.com>, linux-kernel@...r.kernel.org,
 linux-kselftest@...r.kernel.org
Subject: Re: [PATCH v1 1/2] selftests/x86/ldt_gdt: Skip int80 if not supported

On 1/23/26 08:54, Borislav Petkov wrote:
> Hmmm, so, my gut feeling tells me that we need a proper ia32 emu support
> detection in the running kernel. I can't find one after a short grep, maybe it
> should be in /proc/cpuinfo, maybe it should be a syscall which fails when
> IA32_EMULATION is off or maybe ptrace(2) says somewhere in the depths of its
> countless ops that it does support IA32 emulation.

Yeah, a little arch_prctl() that returns supported or not would be nice.
I just hope we can manage to keep it used by the selftests and not get
abused by anyone else.