x86, realmode: read cr4 and EFER from kernel for 64-bit trampoline

This patch changes 64-bit trampoline so that CR4 and
EFER are provided by the kernel instead of using fixed
values.

Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@intel.com>
Link: http://lkml.kernel.org/r/1336501366-28617-24-git-send-email-jarkko.sakkinen@intel.com
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

2 files changed, 10 insertions, 0 deletions

diff --git a/arch/x86/kernel/realmode.c b/arch/x86/kernel/realmode.c
index 712fba8fd774..66ac276cf361 100644
--- a/arch/x86/kernel/realmode.c
+++ b/arch/x86/kernel/realmode.c
@@ -6,6 +6,7 @@
 #include <asm/realmode.h>
 
 struct real_mode_header *real_mode_header;
+u32 *trampoline_cr4_features;
 
 void __init setup_real_mode(void)
 {
@@ -64,7 +65,14 @@ void __init setup_real_mode(void)
         trampoline_header->gdt_limit = __BOOT_DS + 7;
         trampoline_header->gdt_base = __pa(boot_gdt);
 #else
+        if (rdmsr_safe(MSR_EFER, &trampoline_header->efer_low,
+                       &trampoline_header->efer_high))
+                BUG();
+
         trampoline_header->start = (u64) secondary_startup_64;
+        trampoline_cr4_features = &trampoline_header->cr4;
+        *trampoline_cr4_features = read_cr4();
+
         trampoline_pgd = (u64 *) __va(real_mode_header->trampoline_pgd);
         trampoline_pgd[0] = __pa(level3_ident_pgt) + _KERNPG_TABLE;
         trampoline_pgd[511] = __pa(level3_kernel_pgt) + _KERNPG_TABLE;
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 7a14fece9cfc..efcf305210a4 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -975,6 +975,8 @@ void __init setup_arch(char **cmdline_p)
         if (boot_cpu_data.cpuid_level >= 0) {
                 /* A CPU has %cr4 if and only if it has CPUID */
                 mmu_cr4_features = read_cr4();
+                if (trampoline_cr4_features)
+                        *trampoline_cr4_features = mmu_cr4_features;
         }
 
 #ifdef CONFIG_X86_32