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

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Message-ID: <20250103065631.26459-1-jgross@suse.com>
Date: Fri,  3 Jan 2025 07:56:31 +0100
From: Juergen Gross <jgross@...e.com>
To: linux-kernel@...r.kernel.org,
	x86@...nel.org
Cc: Juergen Gross <jgross@...e.com>,
	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>,
	Borislav Petkov <bp@...en8.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Marek Marczykowski-Górecki <marmarek@...isiblethingslab.com>
Subject: [PATCH] x86/execmem: fix ROX cache usage in Xen PV guests

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