On Thu, Apr 22, 2010 at 02:13:04PM +0800, Xiao Guangrong wrote:
> If have new mapping to the unsync page(i.e, add a new parent), just
> update the page from sp->gfn but not write-protect gfn, and if need
> create new shadow page form sp->gfn, we should sync it
>
> Signed-off-by: Xiao Guangrong <xiaoguangrong@xxxxxxxxxxxxxx>
> ---
> arch/x86/kvm/mmu.c | 27 +++++++++++++++++++--------
> 1 files changed, 19 insertions(+), 8 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index fd027a6..8607a64 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -1196,16 +1196,20 @@ static void kvm_unlink_unsync_page(struct kvm *kvm, struct kvm_mmu_page *sp)
>
> static int kvm_mmu_zap_page(struct kvm *kvm, struct kvm_mmu_page *sp);
>
> -static int kvm_sync_page(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp)
> +static int kvm_sync_page(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
> + bool clear_unsync)
> {
> if (sp->role.cr4_pae != !!is_pae(vcpu)) {
> kvm_mmu_zap_page(vcpu->kvm, sp);
> return 1;
> }
>
> - if (rmap_write_protect(vcpu->kvm, sp->gfn))
> - kvm_flush_remote_tlbs(vcpu->kvm);
> - kvm_unlink_unsync_page(vcpu->kvm, sp);
> + if (clear_unsync) {
> + if (rmap_write_protect(vcpu->kvm, sp->gfn))
> + kvm_flush_remote_tlbs(vcpu->kvm);
> + kvm_unlink_unsync_page(vcpu->kvm, sp);
> + }
> +
> if (vcpu->arch.mmu.sync_page(vcpu, sp)) {
> kvm_mmu_zap_page(vcpu->kvm, sp);
> return 1;
> @@ -1293,7 +1297,7 @@ static void mmu_sync_children(struct kvm_vcpu *vcpu,
> kvm_flush_remote_tlbs(vcpu->kvm);
>
> for_each_sp(pages, sp, parents, i) {
> - kvm_sync_page(vcpu, sp);
> + kvm_sync_page(vcpu, sp, true);
> mmu_pages_clear_parents(&parents);
> }
> cond_resched_lock(&vcpu->kvm->mmu_lock);
> @@ -1313,7 +1317,7 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu,
> unsigned index;
> unsigned quadrant;
> struct hlist_head *bucket;
> - struct kvm_mmu_page *sp;
> + struct kvm_mmu_page *sp, *unsync_sp = NULL;
> struct hlist_node *node, *tmp;
>
> role = vcpu->arch.mmu.base_role;
> @@ -1332,12 +1336,16 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu,
> hlist_for_each_entry_safe(sp, node, tmp, bucket, hash_link)
> if (sp->gfn == gfn) {
> if (sp->unsync)
> - if (kvm_sync_page(vcpu, sp))
> - continue;
> + unsync_sp = sp;
Xiao,
I don't see a reason why you can't create a new mapping to an unsync
page. The code already creates shadow pte entries using unsync
pagetables.
So all you need would be to kvm_sync_pages before write protecting.
Also make sure kvm_sync_pages is in place here before enabling multiple
unsync shadows, in the patch series.
>
> if (sp->role.word != role.word)
> continue;
>
> + if (unsync_sp && kvm_sync_page(vcpu, unsync_sp, false)) {
> + unsync_sp = NULL;
> + continue;
> + }
> +
> mmu_page_add_parent_pte(vcpu, sp, parent_pte);
> if (sp->unsync_children) {
> set_bit(KVM_REQ_MMU_SYNC, &vcpu->requests);
> @@ -1346,6 +1354,9 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu,
> trace_kvm_mmu_get_page(sp, false);
> return sp;
> }
> + if (unsync_sp)
> + kvm_sync_page(vcpu, unsync_sp, true);
> +
> ++vcpu->kvm->stat.mmu_cache_miss;
> sp = kvm_mmu_alloc_page(vcpu, parent_pte);
> if (!sp)
> --
> 1.6.1.2
>
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