linux-kernel - Re: [patch 1/2] x86,module: Detect VMX modules and disable Split-Lock-Detect

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Date:   Fri, 3 Apr 2020 20:35:15 +0200
From:   Jessica Yu <jeyu@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Sean Christopherson <sean.j.christopherson@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        "Kenneth R. Crudup" <kenny@...ix.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Xiaoyao Li <xiaoyao.li@...el.com>,
        Nadav Amit <namit@...are.com>,
        Thomas Hellstrom <thellstrom@...are.com>,
        Tony Luck <tony.luck@...el.com>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [patch 1/2] x86,module: Detect VMX modules and disable
 Split-Lock-Detect

+++ Peter Zijlstra [03/04/20 18:41 +0200]:
>On Fri, Apr 03, 2020 at 09:36:05AM -0700, Sean Christopherson wrote:
>> On Thu, Apr 02, 2020 at 02:32:59PM +0200, Thomas Gleixner wrote:
>> > --- a/arch/x86/kernel/module.c
>> > +++ b/arch/x86/kernel/module.c
>> > @@ -24,6 +24,7 @@
>> >  #include <asm/pgtable.h>
>> >  #include <asm/setup.h>
>> >  #include <asm/unwind.h>
>> > +#include <asm/cpu.h>
>> >
>> >  #if 0
>> >  #define DEBUGP(fmt, ...)				\
>> > @@ -253,6 +254,11 @@ int module_finalize(const Elf_Ehdr *hdr,
>> >  					    tseg, tseg + text->sh_size);
>> >  	}
>> >
>> > +	if (text && !me->sld_safe) {
>>
>> As also reported by the test bot, sld_safe only exist if CPU_SUP_INTEL=y.
>>
>> This can also be conditioned on boot_cpu_has(X86_FEATURE_VMX), or the
>> static variant.  If CPU_SUP_INTEL=y, X86_FEATURE_VMX will be set if and
>> only if VMX is fully enabled, i.e. supported by the CPU and enabled in
>> MSR_IA32_FEATURE_CONTROl.
>>
>> > +		void *tseg = (void *)text->sh_addr;
>> > +		split_lock_validate_module_text(me, tseg, tseg + text->sh_size);
>> > +	}
>
>Ideally we push it all into arch code, but load_info isn't exposed to
>arch module code :/.

Hm, I can look into exposing load_info to arch module code and will
post a patch on Monday.

Jessica