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>

7 files changed, 49 insertions, 28 deletions

diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 4fa7dcceb6c0..404583ccf0cf 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -544,13 +544,16 @@ static inline void load_sp0(struct tss_struct *tss,
  * enable), so that any CPU's that boot up
  * after us can get the correct flags.
  */
-extern unsigned long            mmu_cr4_features;
+extern unsigned long mmu_cr4_features;
+extern u32 *trampoline_cr4_features;
 
 static inline void set_in_cr4(unsigned long mask)
 {
         unsigned long cr4;
 
         mmu_cr4_features |= mask;
+        if (trampoline_cr4_features)
+                *trampoline_cr4_features = mmu_cr4_features;
         cr4 = read_cr4();
         cr4 |= mask;
         write_cr4(cr4);
@@ -561,6 +564,8 @@ static inline void clear_in_cr4(unsigned long mask)
         unsigned long cr4;
 
         mmu_cr4_features &= ~mask;
+        if (trampoline_cr4_features)
+                *trampoline_cr4_features = mmu_cr4_features;
         cr4 = read_cr4();
         cr4 &= ~mask;
         write_cr4(cr4);
diff --git a/arch/x86/include/asm/realmode.h b/arch/x86/include/asm/realmode.h
index 1421eed1c8e8..937dc6071d76 100644
--- a/arch/x86/include/asm/realmode.h
+++ b/arch/x86/include/asm/realmode.h
@@ -24,18 +24,22 @@ struct real_mode_header {
 #ifdef CONFIG_X86_32
         u32     machine_real_restart_asm;
 #endif
-} __attribute__((__packed__));
+};
 
 /* This must match data at trampoline_32/64.S */
 struct trampoline_header {
 #ifdef CONFIG_X86_32
         u32 start;
+        u16 gdt_pad;
         u16 gdt_limit;
         u32 gdt_base;
 #else
         u64 start;
+        u32 cr4;
+        u32 efer_low;
+        u32 efer_high;
 #endif
-} __attribute__((__packed__));
+};
 
 extern struct real_mode_header *real_mode_header;
 extern unsigned char real_mode_blob_end[];
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
diff --git a/arch/x86/realmode/rm/header.S b/arch/x86/realmode/rm/header.S
index b4c32632bf16..4612d5382791 100644
--- a/arch/x86/realmode/rm/header.S
+++ b/arch/x86/realmode/rm/header.S
@@ -9,6 +9,7 @@
 
         .section ".header", "a"
 
+        .balign 16
 GLOBAL(real_mode_header)
         .long   pa_text_start
         .long   pa_ro_end
diff --git a/arch/x86/realmode/rm/trampoline_64.S b/arch/x86/realmode/rm/trampoline_64.S
index 3f7293239365..66e26f088288 100644
--- a/arch/x86/realmode/rm/trampoline_64.S
+++ b/arch/x86/realmode/rm/trampoline_64.S
@@ -34,9 +34,9 @@
 #include "realmode.h"
 
         .text
-        .balign PAGE_SIZE
         .code16
 
+        .balign PAGE_SIZE
 ENTRY(trampoline_start)
         cli                     # We should be safe anyway
         wbinvd
@@ -65,8 +65,8 @@ ENTRY(trampoline_start)
          * to 32 bit.
          */
 
-        lidtl   tidt    # load idt with 0, 0
-        lgdtl   tgdt    # load gdt with whatever is appropriate
+        lidtl   tr_idt  # load idt with 0, 0
+        lgdtl   tr_gdt  # load gdt with whatever is appropriate
 
         movw    $__KERNEL_DS, %dx       # Data segment descriptor
 
@@ -93,16 +93,17 @@ ENTRY(startup_32)
         movl    %edx, %fs
         movl    %edx, %gs
 
-        movl    $X86_CR4_PAE, %eax
+        movl    pa_tr_cr4, %eax
         movl    %eax, %cr4              # Enable PAE mode
 
         # Setup trampoline 4 level pagetables
         movl    $pa_trampoline_pgd, %eax
         movl    %eax, %cr3
 
+        # Set up EFER
+        movl    pa_tr_efer, %eax
+        movl    pa_tr_efer + 4, %edx
         movl    $MSR_EFER, %ecx
-        movl    $((1 << _EFER_LME) | (1 << _EFER_NX)), %eax     # Enable Long Mode
-        xorl    %edx, %edx
         wrmsr
 
         # Enable paging and in turn activate Long Mode
@@ -124,23 +125,4 @@ ENTRY(startup_64)
         # Now jump into the kernel using virtual addresses
         jmpq    *tr_start(%rip)
 
-        .section ".rodata","a"
-        .balign 16
-tidt:
-        .word   0                       # idt limit = 0
-        .word   0, 0                    # idt base = 0L
-
-        # Duplicate the global descriptor table
-        # so the kernel can live anywhere
-        .balign 16
-        .globl tgdt
-tgdt:
-        .short  tgdt_end - tgdt - 1     # gdt limit
-        .long   pa_tgdt
-        .short  0
-        .quad   0x00cf9b000000ffff      # __KERNEL32_CS
-        .quad   0x00af9b000000ffff      # __KERNEL_CS
-        .quad   0x00cf93000000ffff      # __KERNEL_DS
-tgdt_end:
-
 #include "trampoline_common.S"
diff --git a/arch/x86/realmode/rm/trampoline_common.S b/arch/x86/realmode/rm/trampoline_common.S
index c3f951c468c5..cac444b942f8 100644
--- a/arch/x86/realmode/rm/trampoline_common.S
+++ b/arch/x86/realmode/rm/trampoline_common.S
@@ -1,5 +1,20 @@
         .section ".rodata","a"
 
+#ifdef CONFIG_X86_64
+        # Duplicate the global descriptor table
+        # so the kernel can live anywhere
+        .balign 16
+        .globl tr_gdt
+tr_gdt:
+        .short  tr_gdt_end - tr_gdt - 1 # gdt limit
+        .long   pa_tr_gdt
+        .short  0
+        .quad   0x00cf9b000000ffff      # __KERNEL32_CS
+        .quad   0x00af9b000000ffff      # __KERNEL_CS
+        .quad   0x00cf93000000ffff      # __KERNEL_DS
+tr_gdt_end:
+#endif
+
         .balign 4
 tr_idt: .fill 1, 6, 0
 
@@ -8,12 +23,16 @@ tr_idt: .fill 1, 6, 0
         .balign 4
 GLOBAL(trampoline_status)       .space  4
 
+        .balign 8
 GLOBAL(trampoline_header)
 #ifdef CONFIG_X86_32
         tr_start:               .space  4
+        tr_gdt_pad:             .space  2
         tr_gdt:                 .space  6
 #else
         tr_start:               .space  8
+        GLOBAL(tr_cr4)          .space  4
+        GLOBAL(tr_efer)         .space  8
 #endif
 END(trampoline_header)