linux-kernel - Re: [PATCH] x86/execmem: fix ROX cache usage in Xen PV guests

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Message-ID: <20250103130044.GEZ3fffHPSmJ3ngPXn@fat_crate.local>
Date: Fri, 3 Jan 2025 14:00:44 +0100
From: Borislav Petkov <bp@...en8.de>
To: Juergen Gross <jgross@...e.com>
Cc: linux-kernel@...r.kernel.org, x86@...nel.org,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Andy Lutomirski <luto@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, "H. Peter Anvin" <hpa@...or.com>,
	Marek Marczykowski-Górecki <marmarek@...isiblethingslab.com>,
	Mike Rapoport <rppt@...nel.org>
Subject: Re: [PATCH] x86/execmem: fix ROX cache usage in Xen PV guests

Adding the author in Fixes to Cc

On Fri, Jan 03, 2025 at 07:56:31AM +0100, Juergen Gross wrote:
> The recently introduced ROX cache for modules is assuming large page
> support in 64-bit mode without testing the related feature bit. This
> results in breakage when running as a Xen PV guest, as in this mode
> large pages are not supported.
> 
> Fix that by testing the X86_FEATURE_PSE capability when deciding
> whether to enable the ROX cache.
> 
> Fixes: 2e45474ab14f ("execmem: add support for cache of large ROX pages")
> Reported-by: Marek Marczykowski-Górecki <marmarek@...isiblethingslab.com>
> Tested-by: Marek Marczykowski-Górecki <marmarek@...isiblethingslab.com>
> Signed-off-by: Juergen Gross <jgross@...e.com>
> ---
>  arch/x86/mm/init.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
> index c6d29f283001..62aa4d66a032 100644
> --- a/arch/x86/mm/init.c
> +++ b/arch/x86/mm/init.c
> @@ -1080,7 +1080,8 @@ struct execmem_info __init *execmem_arch_setup(void)
>  
>  	start = MODULES_VADDR + offset;
>  
> -	if (IS_ENABLED(CONFIG_ARCH_HAS_EXECMEM_ROX)) {
> +	if (IS_ENABLED(CONFIG_ARCH_HAS_EXECMEM_ROX) &&
> +	    cpu_feature_enabled(X86_FEATURE_PSE)) {
>  		pgprot = PAGE_KERNEL_ROX;
>  		flags = EXECMEM_KASAN_SHADOW | EXECMEM_ROX_CACHE;
>  	} else {
> -- 
> 2.43.0
> 

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette