KVM: Allow dynamic allocation of the mmu shadow cache size

The user is now able to set how many mmu pages will be allocated to the guest.

Signed-off-by: Izik Eidus <izike@qumranet.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

1 files changed, 38 insertions, 2 deletions

diff --git a/drivers/kvm/mmu.c b/drivers/kvm/mmu.c
index 72757db15065..6cda1feb9a95 100644
--- a/drivers/kvm/mmu.c
+++ b/drivers/kvm/mmu.c
@@ -747,6 +747,40 @@ static void kvm_mmu_zap_page(struct kvm *kvm,
         kvm_mmu_reset_last_pte_updated(kvm);
 }
 
+/*
+ * Changing the number of mmu pages allocated to the vm
+ * Note: if kvm_nr_mmu_pages is too small, you will get dead lock
+ */
+void kvm_mmu_change_mmu_pages(struct kvm *kvm, unsigned int kvm_nr_mmu_pages)
+{
+        /*
+         * If we set the number of mmu pages to be smaller be than the
+         * number of actived pages , we must to free some mmu pages before we
+         * change the value
+         */
+
+        if ((kvm->n_alloc_mmu_pages - kvm->n_free_mmu_pages) >
+            kvm_nr_mmu_pages) {
+                int n_used_mmu_pages = kvm->n_alloc_mmu_pages
+                                       - kvm->n_free_mmu_pages;
+
+                while (n_used_mmu_pages > kvm_nr_mmu_pages) {
+                        struct kvm_mmu_page *page;
+
+                        page = container_of(kvm->active_mmu_pages.prev,
+                                            struct kvm_mmu_page, link);
+                        kvm_mmu_zap_page(kvm, page);
+                        n_used_mmu_pages--;
+                }
+                kvm->n_free_mmu_pages = 0;
+        }
+        else
+                kvm->n_free_mmu_pages += kvm_nr_mmu_pages
+                                         - kvm->n_alloc_mmu_pages;
+
+        kvm->n_alloc_mmu_pages = kvm_nr_mmu_pages;
+}
+
 static int kvm_mmu_unprotect_page(struct kvm_vcpu *vcpu, gfn_t gfn)
 {
         unsigned index;
@@ -1297,8 +1331,10 @@ static int alloc_mmu_pages(struct kvm_vcpu *vcpu)
 
         ASSERT(vcpu);
 
-        vcpu->kvm->n_free_mmu_pages = KVM_NUM_MMU_PAGES;
-
+        if (vcpu->kvm->n_requested_mmu_pages)
+                vcpu->kvm->n_free_mmu_pages = vcpu->kvm->n_requested_mmu_pages;
+        else
+                vcpu->kvm->n_free_mmu_pages = vcpu->kvm->n_alloc_mmu_pages;
         /*
          * When emulating 32-bit mode, cr3 is only 32 bits even on x86_64.
          * Therefore we need to allocate shadow page tables in the first