Using PTE_LIST_WRITE_PROTECT bit in rmap store the write-protect status to avoid unnecessary shadow page walking
Also if no shadow page is indirect, the page is write-free 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 84b9775..3887a07 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -797,6 +797,7 @@ static int mapping_level(struct kvm_vcpu *vcpu, gfn_t large_gfn) } #define PTE_LIST_DESC (0x1ull) +#define PTE_LIST_WRITE_PROTECT (0x2ull) #define PTE_LIST_FLAG_MASK (0x3ull) static void @@ -1016,6 +1017,13 @@ static bool rmap_can_add(struct kvm_vcpu *vcpu) return mmu_memory_cache_free_objects(cache); } +static void host_page_write_protect(u64 *spte, unsigned long *rmapp) +{ + if (!(*spte & SPTE_HOST_WRITEABLE) && + !(*rmapp & PTE_LIST_WRITE_PROTECT)) + *rmapp |= PTE_LIST_WRITE_PROTECT; +} + static int rmap_add(struct kvm_vcpu *vcpu, u64 *spte, gfn_t gfn) { struct kvm_mmu_page *sp; @@ -1023,7 +1031,10 @@ static int rmap_add(struct kvm_vcpu *vcpu, u64 *spte, gfn_t gfn) sp = page_header(__pa(spte)); kvm_mmu_page_set_gfn(sp, spte - sp->spt, gfn); + rmapp = gfn_to_rmap(vcpu->kvm, gfn, sp->role.level); + host_page_write_protect(spte, rmapp); + return pte_list_add(vcpu, spte, rmapp); } @@ -1130,8 +1141,17 @@ static int rmap_write_protect(struct kvm *kvm, u64 gfn) int write_protected = 0; slot = gfn_to_memslot(kvm, gfn); + rmapp = __gfn_to_rmap(gfn, PT_PAGE_TABLE_LEVEL, slot); - for (i = PT_PAGE_TABLE_LEVEL; + if (*rmapp & PTE_LIST_WRITE_PROTECT) + return 0; + + *rmapp |= PTE_LIST_WRITE_PROTECT; + + write_protected |= __rmap_write_protect(kvm, rmapp, + PT_PAGE_TABLE_LEVEL); + + for (i = PT_DIRECTORY_LEVEL; i < PT_PAGE_TABLE_LEVEL + KVM_NR_PAGE_SIZES; ++i) { rmapp = __gfn_to_rmap(gfn, i, slot); write_protected |= __rmap_write_protect(kvm, rmapp, i); @@ -1180,6 +1200,7 @@ static int kvm_set_pte_rmapp(struct kvm *kvm, unsigned long *rmapp, new_spte &= ~shadow_accessed_mask; mmu_spte_clear_track_bits(spte); mmu_spte_set(spte, new_spte); + host_page_write_protect(spte, rmapp); spte = rmap_next(rmapp, spte); } } @@ -2247,8 +2268,16 @@ static int mmu_need_write_protect(struct kvm_vcpu *vcpu, gfn_t gfn, { struct kvm_mmu_page *s; struct hlist_node *node; + unsigned long *rmap; bool need_unsync = false; + if (!vcpu->kvm->arch.indirect_shadow_pages) + return 0; + + rmap = gfn_to_rmap(vcpu->kvm, gfn, PT_PAGE_TABLE_LEVEL); + if (!(*rmap & PTE_LIST_WRITE_PROTECT)) + return 0; + for_each_gfn_indirect_valid_sp(vcpu->kvm, s, gfn, node) { if (!can_unsync) return 1; @@ -2262,6 +2291,9 @@ static int mmu_need_write_protect(struct kvm_vcpu *vcpu, gfn_t gfn, } if (need_unsync) kvm_unsync_pages(vcpu, gfn); + + *rmap &= ~PTE_LIST_WRITE_PROTECT; + 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
