xen: allow set_pte_at on init_mm to be lockless (2bd50036) · Commits · 戴 / test

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>

arch/x86/xen/mmu.c

+10 −2

Original line number	Diff line number	Diff line
		@@ -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)

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