xen: setup percpu data pointers

Impact: fix xen booting

We need to access percpu data fairly early, so set up the percpu
registers as soon as possible.  We only need to load the appropriate
segment register.  We already have a GDT, but its hard to change it
early because we need to manipulate the pagetable to do so, and that
hasn't been set up yet.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

2 files changed, 7 insertions, 1 deletions

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index bef941f61451..fe19c88a5029 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -1647,6 +1647,9 @@ asmlinkage void __init xen_start_kernel(void)
         have_vcpu_info_placement = 0;
 #endif
 
+        /* setup percpu state */
+        load_percpu_segment(0);
+
         xen_smp_init();
 
         /* Get mfn list */
diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
index 7735e3dd359c..88d5d5ec6beb 100644
--- a/arch/x86/xen/smp.c
+++ b/arch/x86/xen/smp.c
@@ -170,7 +170,8 @@ static void __init xen_smp_prepare_boot_cpu(void)
 
         /* We've switched to the "real" per-cpu gdt, so make sure the
            old memory can be recycled */
-        make_lowmem_page_readwrite(&per_cpu_var(gdt_page));
+        make_lowmem_page_readwrite(__per_cpu_load +
+                                   (unsigned long)&per_cpu_var(gdt_page));
 
         xen_setup_vcpu_info_placement();
 }
@@ -235,6 +236,8 @@ cpu_initialize_context(unsigned int cpu, struct task_struct *idle)
         ctxt->user_regs.ss = __KERNEL_DS;
 #ifdef CONFIG_X86_32
         ctxt->user_regs.fs = __KERNEL_PERCPU;
+#else
+        ctxt->gs_base_kernel = per_cpu_offset(cpu);
 #endif
         ctxt->user_regs.eip = (unsigned long)cpu_bringup_and_idle;
         ctxt->user_regs.eflags = 0x1000; /* IOPL_RING1 */