linux-kernel - Re: [PATCH 3/3] x86: Disable running 32bit processes if ia32

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Message-ID: <87cz27juso.ffs@tglx>
Date:   Wed, 07 Jun 2023 14:55:51 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Nikolay Borisov <nik.borisov@...e.com>, x86@...nel.org
Cc:     linux-kernel@...r.kernel.org, mhocko@...e.com, jslaby@...e.cz,
        Nikolay Borisov <nik.borisov@...e.com>
Subject: Re: [PATCH 3/3] x86: Disable running 32bit processes if
 ia32_disabled is passed

On Wed, Jun 07 2023 at 14:01, Thomas Gleixner wrote:
> On Wed, Jun 07 2023 at 10:29, Nikolay Borisov wrote:
>> @@ -2368,4 +2373,7 @@ void arch_smt_update(void)
>>  	cpu_bugs_smt_update();
>>  	/* Check whether IPI broadcasting can be enabled */
>>  	apic_smt_update();
>> +	if (ia32_disabled)
>> +		on_each_cpu(remove_user32cs_from_gdt, NULL, 1);

My brain based compiler tells me, that this breaks the 32bit build and
the 64bit build with CONFIG_IA32_EMULATION=n. I'm pretty confident that
a real compiler will agree.