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>
This commit is contained in:
Jeremy Fitzhardinge 2008-07-08 15:06:42 -07:00 committed by Ingo Molnar
parent a9e7062d73
commit 5b09b2876e
4 changed files with 40 additions and 3 deletions

View File

@ -39,6 +39,13 @@ static struct x8664_pda *__cpu_pda[NR_CPUS] __initdata;
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 @@ void __init x86_64_start_kernel(char * real_mode_data)
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");

View File

@ -971,6 +971,7 @@ void xen_setup_vcpu_info_placement(void)
/* xen_vcpu_setup managed to place the vcpu_info within the
percpu area for all cpus, so make use of it */
#ifdef CONFIG_X86_32
if (have_vcpu_info_placement) {
printk(KERN_INFO "Xen: using vcpu_info placement\n");
@ -980,6 +981,7 @@ void xen_setup_vcpu_info_placement(void)
pv_irq_ops.irq_enable = xen_irq_enable_direct;
pv_mmu_ops.read_cr2 = xen_read_cr2_direct;
}
#endif
}
static unsigned xen_patch(u8 type, u16 clobbers, void *insnbuf,
@ -1000,10 +1002,12 @@ static unsigned xen_patch(u8 type, u16 clobbers, void *insnbuf,
goto patch_site
switch (type) {
#ifdef CONFIG_X86_32
SITE(pv_irq_ops, irq_enable);
SITE(pv_irq_ops, irq_disable);
SITE(pv_irq_ops, save_fl);
SITE(pv_irq_ops, restore_fl);
#endif /* CONFIG_X86_32 */
#undef SITE
patch_site:
@ -1323,6 +1327,7 @@ asmlinkage void __init xen_start_kernel(void)
#ifdef CONFIG_X86_64
/* Disable until direct per-cpu data access. */
have_vcpu_info_placement = 0;
x86_64_init_pda();
#endif
xen_smp_init();

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@ -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__

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@ -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);