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 09:36:05 -0700
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        "Kenneth R. Crudup" <kenny@...ix.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Jessica Yu <jeyu@...nel.org>,
        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

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);
> +	}
> +
>  	if (para) {
>  		void *pseg = (void *)para->sh_addr;
>  		apply_paravirt(pseg, pseg + para->sh_size);
> --- a/include/linux/module.h
> +++ b/include/linux/module.h
> @@ -407,6 +407,10 @@ struct module {
>  	bool sig_ok;
>  #endif
>  
> +#ifdef CONFIG_CPU_SUP_INTEL
> +	bool sld_safe;
> +#endif
> +
>  	bool async_probe_requested;
>  
>  	/* symbols that will be GPL-only in the near future. */
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -3096,6 +3096,11 @@ static int check_modinfo(struct module *
>  			"is unknown, you have been warned.\n", mod->name);
>  	}
>  
> +#ifdef CONFIG_CPU_SUP_INTEL
> +	if (get_modinfo(info, "sld_safe"))
> +		mod->sld_safe = true;
> +#endif
> +
>  	err = check_modinfo_livepatch(mod, info);
>  	if (err)
>  		return err;
>