x86/mm/pat: don't collapse pages without PSE set

Collapsing pages to a leaf PMD or PUD should be done only if
X86_FEATURE_PSE is available, which is not the case when running e.g.
as a Xen PV guest.

Fixes: 41d8848 ("x86/mm/pat: restore large ROX pages after fragmentation")
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20250528123557.12847-3-jgross@suse.com

Author: jgross1

arch/x86/mm/pat/set_memory.c

@@ -1257,6 +1257,9 @@ static int collapse_pmd_page(pmd_t *pmd, unsigned long addr,
 	pgprot_t pgprot;
 	int i = 0;
 
+	if (!cpu_feature_enabled(X86_FEATURE_PSE))
+		return 0;
+
 	addr &= PMD_MASK;
 	pte = pte_offset_kernel(pmd, addr);
 	first = *pte;