3 files changed, 19 insertions, 16 deletions
diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
index 8199a6187251..66e42a098d70 100644
--- a/arch/x86/boot/compressed/kaslr.c
+++ b/arch/x86/boot/compressed/kaslr.c
@@ -46,6 +46,12 @@
 #define STATIC
 #include <linux/decompress/mm.h>
 
+#ifdef CONFIG_X86_5LEVEL
+unsigned int pgtable_l5_enabled __ro_after_init;
+unsigned int pgdir_shift __ro_after_init = 39;
+unsigned int ptrs_per_p4d __ro_after_init = 1;
+#endif
+
 extern unsigned long get_cmd_line_ptr(void);
 
 /* Simplified build-specific string for starting entropy. */
@@ -723,6 +729,14 @@ void choose_random_location(unsigned long input,
 		return;
 	}
 
+#ifdef CONFIG_X86_5LEVEL
+	if (__read_cr4() & X86_CR4_LA57) {
+		pgtable_l5_enabled = 1;
+		pgdir_shift = 48;
+		ptrs_per_p4d = 512;
+	}
+#endif
+
 	boot_params->hdr.loadflags |= KASLR_FLAG;
 
 	/* Prepare to add new identity pagetables on demand. */
diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
index 98761a1576ce..b50c42455e25 100644
--- a/arch/x86/boot/compressed/misc.c
+++ b/arch/x86/boot/compressed/misc.c
@@ -169,16 +169,6 @@ void __puthex(unsigned long value)
 	}
 }
 
-static bool l5_supported(void)
-{
-	/* Check if leaf 7 is supported. */
-	if (native_cpuid_eax(0) < 7)
-		return 0;
-
-	/* Check if la57 is supported. */
-	return native_cpuid_ecx(7) & (1 << (X86_FEATURE_LA57 & 31));
-}
-
 #if CONFIG_X86_NEED_RELOCS
 static void handle_relocations(void *output, unsigned long output_len,
 			       unsigned long virt_addr)
@@ -372,12 +362,6 @@ asmlinkage __visible void *extract_kernel(void *rmode, memptr heap,
 	console_init();
 	debug_putstr("early console in extract_kernel\n");
 
-	if (IS_ENABLED(CONFIG_X86_5LEVEL) && !l5_supported()) {
-		error("This linux kernel as configured requires 5-level paging\n"
-			"This CPU does not support the required 'cr4.la57' feature\n"
-			"Unable to boot - please use a kernel appropriate for your CPU\n");
-	}
-
 	free_mem_ptr     = heap;	/* Heap */
 	free_mem_end_ptr = heap + BOOT_HEAP_SIZE;
 
diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
index 9d323dc6b159..4d369c308ed7 100644
--- a/arch/x86/boot/compressed/misc.h
+++ b/arch/x86/boot/compressed/misc.h
@@ -12,6 +12,11 @@
 #undef CONFIG_PARAVIRT_SPINLOCKS
 #undef CONFIG_KASAN
 
+#ifdef CONFIG_X86_5LEVEL
+/* cpu_feature_enabled() cannot be used that early */
+#define pgtable_l5_enabled __pgtable_l5_enabled
+#endif
+
 #include <linux/linkage.h>
 #include <linux/screen_info.h>
 #include <linux/elf.h>