x86_64: add workaround for no %gs-based percpu
As a stopgap until Mike Travis's x86-64 gs-based percpu patches are
ready, provide workaround functions for x86_read/write_percpu for
Xen's use.
Specifically, this means that we can't really make use of vcpu
placement, because we can't use a single gs-based memory access to get
to vcpu fields. So disable all that for now.
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Stephen Tweedie <sct@redhat.com>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index c978198..1b318e9 100644
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -39,6 +39,13 @@
static struct x8664_pda *__cpu_pda[NR_CPUS] __read_mostly;
#endif
+void __init x86_64_init_pda(void)
+{
+ _cpu_pda = __cpu_pda;
+ cpu_pda(0) = &_boot_cpu_pda;
+ pda_init(0);
+}
+
static void __init zap_identity_mappings(void)
{
pgd_t *pgd = pgd_offset_k(0UL);
@@ -102,9 +109,7 @@
early_printk("Kernel alive\n");
- _cpu_pda = __cpu_pda;
- cpu_pda(0) = &_boot_cpu_pda;
- pda_init(0);
+ x86_64_init_pda();
early_printk("Kernel really alive\n");