Merge branch 'WIP.x86-pti.entry-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 syscall entry code changes for PTI from Ingo Molnar:
 "The main changes here are Andy Lutomirski's changes to switch the
  x86-64 entry code to use the 'per CPU entry trampoline stack'. This,
  besides helping fix KASLR leaks (the pending Page Table Isolation
  (PTI) work), also robustifies the x86 entry code"

* 'WIP.x86-pti.entry-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (26 commits)
  x86/cpufeatures: Make CPU bugs sticky
  x86/paravirt: Provide a way to check for hypervisors
  x86/paravirt: Dont patch flush_tlb_single
  x86/entry/64: Make cpu_entry_area.tss read-only
  x86/entry: Clean up the SYSENTER_stack code
  x86/entry/64: Remove the SYSENTER stack canary
  x86/entry/64: Move the IST stacks into struct cpu_entry_area
  x86/entry/64: Create a per-CPU SYSCALL entry trampoline
  x86/entry/64: Return to userspace from the trampoline stack
  x86/entry/64: Use a per-CPU trampoline stack for IDT entries
  x86/espfix/64: Stop assuming that pt_regs is on the entry stack
  x86/entry/64: Separate cpu_current_top_of_stack from TSS.sp0
  x86/entry: Remap the TSS into the CPU entry area
  x86/entry: Move SYSENTER_stack to the beginning of struct tss_struct
  x86/dumpstack: Handle stack overflow on all stacks
  x86/entry: Fix assumptions that the HW TSS is at the beginning of cpu_tss
  x86/kasan/64: Teach KASAN about the cpu_entry_area
  x86/mm/fixmap: Generalize the GDT fixmap mechanism, introduce struct cpu_entry_area
  x86/entry/gdt: Put per-CPU GDT remaps in ascending order
  x86/dumpstack: Add get_stack_info() support for the SYSENTER stack
  ...

1 files changed, 9 insertions, 7 deletions

diff --git a/arch/x86/power/cpu.c b/arch/x86/power/cpu.c
index 36a28eddb435e..a7d966964c6f2 100644
--- a/arch/x86/power/cpu.c
+++ b/arch/x86/power/cpu.c
@@ -152,17 +152,19 @@ static void do_fpu_end(void)
 static void fix_processor_context(void)
 {
 	int cpu = smp_processor_id();
-	struct tss_struct *t = &per_cpu(cpu_tss, cpu);
 #ifdef CONFIG_X86_64
 	struct desc_struct *desc = get_cpu_gdt_rw(cpu);
 	tss_desc tss;
 #endif
-	set_tss_desc(cpu, t);	/*
-				 * This just modifies memory; should not be
-				 * necessary. But... This is necessary, because
-				 * 386 hardware has concept of busy TSS or some
-				 * similar stupidity.
-				 */
+
+	/*
+	 * We need to reload TR, which requires that we change the
+	 * GDT entry to indicate "available" first.
+	 *
+	 * XXX: This could probably all be replaced by a call to
+	 * force_reload_TR().
+	 */
+	set_tss_desc(cpu, &get_cpu_entry_area(cpu)->tss.x86_tss);
 
 #ifdef CONFIG_X86_64
 	memcpy(&tss, &desc[GDT_ENTRY_TSS], sizeof(tss_desc));