KVM: MMU: dont hold pagecount reference for mapped sptes pages

When using mmu notifiers, we are allowed to remove the page count
reference tooken by get_user_pages to a specific page that is mapped
inside the shadow page tables.

This is needed so we can balance the pagecount against mapcount
checking.

(Right now kvm increase the pagecount and does not increase the
mapcount when mapping page into shadow page table entry,
so when comparing pagecount against mapcount, you have no
reliable result.)

Signed-off-by: Izik Eidus <[email protected]>
Signed-off-by: Marcelo Tosatti <[email protected]>

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index eca41ae9f453cda6dc61112ab925ce66cdb7fef3..6c67b230e9586bab2953650b8c2b97ed2725f07d 100644 (file)
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -634,9 +634,7 @@ static void rmap_remove(struct kvm *kvm, u64 *spte)
        if (*spte & shadow_accessed_mask)
                kvm_set_pfn_accessed(pfn);
        if (is_writeble_pte(*spte))
-               kvm_release_pfn_dirty(pfn);
-       else
-               kvm_release_pfn_clean(pfn);
+               kvm_set_pfn_dirty(pfn);
        rmapp = gfn_to_rmap(kvm, sp->gfns[spte - sp->spt], sp->role.level);
        if (!*rmapp) {
                printk(KERN_ERR "rmap_remove: %p %llx 0->BUG\n", spte, *spte);
@@ -1877,8 +1875,7 @@ static void mmu_set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
        page_header_update_slot(vcpu->kvm, sptep, gfn);
        if (!was_rmapped) {
                rmap_count = rmap_add(vcpu, sptep, gfn);
-               if (!is_rmap_spte(*sptep))
-                       kvm_release_pfn_clean(pfn);
+               kvm_release_pfn_clean(pfn);
                if (rmap_count > RMAP_RECYCLE_THRESHOLD)
                        rmap_recycle(vcpu, sptep, gfn);
        } else {