Make all sptes to be writable if the gfn become write-free to reduce the later page fault
The idea is from Avi Signed-off-by: Xiao Guangrong <[email protected]> --- arch/x86/kvm/mmu.c | 34 +++++++++++++++++++++++++++++++++- 1 files changed, 33 insertions(+), 1 deletions(-) diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index 578a1e2..efa5d59 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -2323,15 +2323,45 @@ static void kvm_unsync_pages(struct kvm_vcpu *vcpu, gfn_t gfn) } } +/* + * If the gfn become write-free, we make all sptes which point to this + * gfn to be writable. + * Note: we should call mark_page_dirty for the gfn later. + */ +static void rmap_break_page_table_wp(struct kvm_memory_slot *slot, gfn_t gfn) +{ + struct spte_iterator iter; + u64 *sptep; + int i; + + for (i = PT_PAGE_TABLE_LEVEL; + i < PT_PAGE_TABLE_LEVEL + KVM_NR_PAGE_SIZES; i++) { + unsigned long *rmap = __gfn_to_rmap(gfn, i, slot); + + for_each_rmap_spte(rmap, &iter, sptep) { + u64 spte = *sptep; + + if (!is_writable_pte(spte) && + (spte & SPTE_ALLOW_WRITE)) { + spte &= ~SPTE_WRITE_PROTECT; + spte |= PT_WRITABLE_MASK; + mmu_spte_update(sptep, spte); + } + } + } +} + static int mmu_need_write_protect(struct kvm_vcpu *vcpu, gfn_t gfn, bool can_unsync) { + struct kvm_memory_slot *slot; struct kvm_mmu_page *s; struct hlist_node *node; unsigned long *rmap; bool need_unsync = false; - rmap = gfn_to_rmap(vcpu->kvm, gfn, PT_PAGE_TABLE_LEVEL); + slot = gfn_to_memslot(vcpu->kvm, gfn); + rmap = __gfn_to_rmap(gfn, PT_PAGE_TABLE_LEVEL, slot); if (!vcpu->kvm->arch.indirect_shadow_pages) goto write_free; @@ -2353,6 +2383,8 @@ static int mmu_need_write_protect(struct kvm_vcpu *vcpu, gfn_t gfn, if (need_unsync) kvm_unsync_pages(vcpu, gfn); + rmap_break_page_table_wp(slot, gfn); + write_free: __clear_bit(PTE_LIST_WP_BIT, rmap); return 0; -- 1.7.7.6 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
