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xen: allow set_pte_at on init_mm to be lockless

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The usual pagetable locking protocol doesn't seem to apply to updates
to init_mm, so don't rely on preemption being disabled in xen_set_pte_at
on init_mm.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Jeremy Fitzhardinge 2008-04-02 10:54:10 -07:00 committed by Ingo Molnar
parent 41e332b2a2
commit 2bd50036b5
1 changed files with 10 additions and 2 deletions
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12
arch/x86/xen/mmu.c
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@ -156,6 +156,10 @@ void set_pte_mfn(unsigned long vaddr, unsigned long mfn, pgprot_t flags)
void xen_set_pte_at(struct mm_struct *mm, unsigned long addr,
pte_t *ptep, pte_t pteval)
{
/* updates to init_mm may be done without lock */
if (mm == &init_mm)
preempt_disable();
if (mm == current->mm || mm == &init_mm) {
if (paravirt_get_lazy_mode() == PARAVIRT_LAZY_MMU) {
struct multicall_space mcs;
@ -163,12 +167,16 @@ void xen_set_pte_at(struct mm_struct *mm, unsigned long addr,
MULTI_update_va_mapping(mcs.mc, addr, pteval, 0);
xen_mc_issue(PARAVIRT_LAZY_MMU);
return;
goto out;
} else
if (HYPERVISOR_update_va_mapping(addr, pteval, 0) == 0)
return;
goto out;
}
xen_set_pte(ptep, pteval);
out:
if (mm == &init_mm)
preempt_enable();
}
pteval_t xen_pte_val(pte_t pte)