x86/mm: Initialize 'pgtable_l5_enabled' at boot-time

'pgtable_l5_enabled' indicates which paging mode we are using. We need to
initialize it at boot-time according to machine capability.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/20180214182542.69302-2-kirill.shutemov@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
index b18e8f9512de3880b1870dc7584df18d89463e28..d02a838c0ce4dc0af9e318bbed969b037ff1c862 100644 (file)
--- a/arch/x86/boot/compressed/kaslr.c
+++ b/arch/x86/boot/compressed/kaslr.c
@@ -47,7 +47,7 @@
 #include <linux/decompress/mm.h>
 
 #ifdef CONFIG_X86_5LEVEL
-unsigned int pgtable_l5_enabled __ro_after_init = 1;
+unsigned int pgtable_l5_enabled __ro_after_init;
 unsigned int pgdir_shift __ro_after_init = 48;
 unsigned int ptrs_per_p4d __ro_after_init = 512;
 #endif
@@ -729,6 +729,12 @@ void choose_random_location(unsigned long input,
                return;
        }
 
+#ifdef CONFIG_X86_5LEVEL
+       if (__read_cr4() & X86_CR4_LA57) {
+               pgtable_l5_enabled = 1;
+       }
+#endif
+
        boot_params->hdr.loadflags |= KASLR_FLAG;
 
        /* Prepare to add new identity pagetables on demand. */

diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index 98b0ff49b220b550c9355f3dcb758a313cac55ce..ffb31c50d5158fc77501f33cad0cea66bda8314c 100644 (file)
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -40,7 +40,7 @@ static unsigned int __initdata next_early_pgt;
 pmdval_t early_pmd_flags = __PAGE_KERNEL_LARGE & ~(_PAGE_GLOBAL | _PAGE_NX);
 
 #ifdef CONFIG_X86_5LEVEL
-unsigned int pgtable_l5_enabled __ro_after_init = 1;
+unsigned int pgtable_l5_enabled __ro_after_init;
 EXPORT_SYMBOL(pgtable_l5_enabled);
 unsigned int pgdir_shift __ro_after_init = 48;
 EXPORT_SYMBOL(pgdir_shift);
@@ -64,6 +64,26 @@ static void __head *fixup_pointer(void *ptr, unsigned long physaddr)
        return ptr - (void *)_text + (void *)physaddr;
 }
 
+#ifdef CONFIG_X86_5LEVEL
+static unsigned int __head *fixup_int(void *ptr, unsigned long physaddr)
+{
+       return fixup_pointer(ptr, physaddr);
+}
+
+static void __head check_la57_support(unsigned long physaddr)
+{
+       if (native_cpuid_eax(0) < 7)
+               return;
+
+       if (!(native_cpuid_ecx(7) & (1 << (X86_FEATURE_LA57 & 31))))
+               return;
+
+       *fixup_int(&pgtable_l5_enabled, physaddr) = 1;
+}
+#else
+static void __head check_la57_support(unsigned long physaddr) {}
+#endif
+
 unsigned long __head __startup_64(unsigned long physaddr,
                                  struct boot_params *bp)
 {
@@ -76,6 +96,8 @@ unsigned long __head __startup_64(unsigned long physaddr,
        int i;
        unsigned int *next_pgt_ptr;
 
+       check_la57_support(physaddr);
+
        /* Is the address too large? */
        if (physaddr >> MAX_PHYSMEM_BITS)
                for (;;);