From 5b09b2876ed1a8e34a0da8f069575fc6174e2077 Mon Sep 17 00:00:00 2001 From: Jeremy Fitzhardinge Date: Tue, 8 Jul 2008 15:06:42 -0700 Subject: 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 Cc: Stephen Tweedie Cc: Eduardo Habkost Cc: Mark McLoughlin Signed-off-by: Ingo Molnar --- include/asm-x86/percpu.h | 26 ++++++++++++++++++++++++++ include/asm-x86/setup.h | 1 + 2 files changed, 27 insertions(+) (limited to 'include/asm-x86') diff --git a/include/asm-x86/percpu.h b/include/asm-x86/percpu.h index 912a3a17b9d..4e91ee1e37a 100644 --- a/include/asm-x86/percpu.h +++ b/include/asm-x86/percpu.h @@ -22,6 +22,32 @@ DECLARE_PER_CPU(struct x8664_pda, pda); +/* + * These are supposed to be implemented as a single instruction which + * operates on the per-cpu data base segment. x86-64 doesn't have + * that yet, so this is a fairly inefficient workaround for the + * meantime. The single instruction is atomic with respect to + * preemption and interrupts, so we need to explicitly disable + * interrupts here to achieve the same effect. However, because it + * can be used from within interrupt-disable/enable, we can't actually + * disable interrupts; disabling preemption is enough. + */ +#define x86_read_percpu(var) \ + ({ \ + typeof(per_cpu_var(var)) __tmp; \ + preempt_disable(); \ + __tmp = __get_cpu_var(var); \ + preempt_enable(); \ + __tmp; \ + }) + +#define x86_write_percpu(var, val) \ + do { \ + preempt_disable(); \ + __get_cpu_var(var) = (val); \ + preempt_enable(); \ + } while(0) + #else /* CONFIG_X86_64 */ #ifdef __ASSEMBLY__ diff --git a/include/asm-x86/setup.h b/include/asm-x86/setup.h index 90ab2225e71..659492624e7 100644 --- a/include/asm-x86/setup.h +++ b/include/asm-x86/setup.h @@ -76,6 +76,7 @@ extern unsigned long init_pg_tables_start; extern unsigned long init_pg_tables_end; #else +void __init x86_64_init_pda(void); void __init x86_64_start_kernel(char *real_mode); void __init x86_64_start_reservations(char *real_mode_data); -- cgit v1.2.3