xen: allow set_pte_at on init_mm to be lockless
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>
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@ -156,6 +156,10 @@ void set_pte_mfn(unsigned long vaddr, unsigned long mfn, pgprot_t flags)
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void xen_set_pte_at(struct mm_struct *mm, unsigned long addr,
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pte_t *ptep, pte_t pteval)
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{
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/* updates to init_mm may be done without lock */
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if (mm == &init_mm)
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preempt_disable();
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if (mm == current->mm || mm == &init_mm) {
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if (paravirt_get_lazy_mode() == PARAVIRT_LAZY_MMU) {
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struct multicall_space mcs;
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@ -163,12 +167,16 @@ void xen_set_pte_at(struct mm_struct *mm, unsigned long addr,
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MULTI_update_va_mapping(mcs.mc, addr, pteval, 0);
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xen_mc_issue(PARAVIRT_LAZY_MMU);
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return;
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goto out;
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} else
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if (HYPERVISOR_update_va_mapping(addr, pteval, 0) == 0)
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return;
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goto out;
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}
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xen_set_pte(ptep, pteval);
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out:
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if (mm == &init_mm)
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preempt_enable();
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}
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pteval_t xen_pte_val(pte_t pte)
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