From 2bd50036b5dfc929390ddc48be7f6314447b2be3 Mon Sep 17 00:00:00 2001 From: Jeremy Fitzhardinge Date: Wed, 2 Apr 2008 10:54:10 -0700 Subject: [PATCH] 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 Signed-off-by: Ingo Molnar Signed-off-by: Thomas Gleixner --- arch/x86/xen/mmu.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c index 272635aaef88..6cbcf65609ad 100644 --- a/arch/x86/xen/mmu.c +++ b/arch/x86/xen/mmu.c @@ -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) -- 2.20.1