KVM: introduce kvm->srcu and convert kvm_set_memory_region to SRCU update

Use two steps for memslot deletion: mark the slot invalid (which stops
instantiation of new shadow pages for that slot, but allows destruction),
then instantiate the new empty slot.

Also simplifies kvm_handle_hva locking.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

3 files changed, 22 insertions, 16 deletions

diff --git a/arch/ia64/kvm/kvm-ia64.c b/arch/ia64/kvm/kvm-ia64.c
index 0757c7027986..b2e4d16dd39e 100644
--- a/arch/ia64/kvm/kvm-ia64.c
+++ b/arch/ia64/kvm/kvm-ia64.c
@@ -1382,7 +1382,7 @@ static void kvm_release_vm_pages(struct kvm *kvm)
         int i, j;
         unsigned long base_gfn;
 
-        slots = kvm->memslots;
+        slots = rcu_dereference(kvm->memslots);
         for (i = 0; i < slots->nmemslots; i++) {
                 memslot = &slots->memslots[i];
                 base_gfn = memslot->base_gfn;
@@ -1837,6 +1837,7 @@ int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm,
         struct kvm_memory_slot *memslot;
         int is_dirty = 0;
 
+        down_write(&kvm->slots_lock);
         spin_lock(&kvm->arch.dirty_log_lock);
 
         r = kvm_ia64_sync_dirty_log(kvm, log);
@@ -1856,6 +1857,7 @@ int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm,
         }
         r = 0;
 out:
+        up_write(&kvm->slots_lock);
         spin_unlock(&kvm->arch.dirty_log_lock);
         return r;
 }
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 81f84d326a84..f8bf42a25995 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -29,6 +29,7 @@
 #include <linux/swap.h>
 #include <linux/hugetlb.h>
 #include <linux/compiler.h>
+#include <linux/srcu.h>
 
 #include <asm/page.h>
 #include <asm/cmpxchg.h>
@@ -807,21 +808,15 @@ static int kvm_handle_hva(struct kvm *kvm, unsigned long hva,
 {
         int i, j;
         int retval = 0;
-        struct kvm_memslots *slots = kvm->memslots;
+        struct kvm_memslots *slots;
+
+        slots = rcu_dereference(kvm->memslots);
 
-        /*
-         * If mmap_sem isn't taken, we can look the memslots with only
-         * the mmu_lock by skipping over the slots with userspace_addr == 0.
-         */
         for (i = 0; i < slots->nmemslots; i++) {
                 struct kvm_memory_slot *memslot = &slots->memslots[i];
                 unsigned long start = memslot->userspace_addr;
                 unsigned long end;
 
-                /* mmu_lock protects userspace_addr */
-                if (!start)
-                        continue;
-
                 end = start + (memslot->npages << PAGE_SHIFT);
                 if (hva >= start && hva < end) {
                         gfn_t gfn_offset = (hva - start) >> PAGE_SHIFT;
@@ -1617,7 +1612,7 @@ static void mmu_unshadow(struct kvm *kvm, gfn_t gfn)
 
 static void page_header_update_slot(struct kvm *kvm, void *pte, gfn_t gfn)
 {
-        int slot = memslot_id(kvm, gfn_to_memslot(kvm, gfn));
+        int slot = memslot_id(kvm, gfn);
         struct kvm_mmu_page *sp = page_header(__pa(pte));
 
         __set_bit(slot, sp->slot_bitmap);
@@ -3021,9 +3016,11 @@ unsigned int kvm_mmu_calculate_mmu_pages(struct kvm *kvm)
         int i;
         unsigned int nr_mmu_pages;
         unsigned int  nr_pages = 0;
+        struct kvm_memslots *slots;
 
-        for (i = 0; i < kvm->memslots->nmemslots; i++)
-                nr_pages += kvm->memslots->memslots[i].npages;
+        slots = rcu_dereference(kvm->memslots);
+        for (i = 0; i < slots->nmemslots; i++)
+                nr_pages += slots->memslots[i].npages;
 
         nr_mmu_pages = nr_pages * KVM_PERMILLE_MMU_PAGES / 1000;
         nr_mmu_pages = max(nr_mmu_pages,
@@ -3293,10 +3290,12 @@ static void audit_mappings(struct kvm_vcpu *vcpu)
 static int count_rmaps(struct kvm_vcpu *vcpu)
 {
         int nmaps = 0;
-        int i, j, k;
+        int i, j, k, idx;
 
+        idx = srcu_read_lock(&kvm->srcu);
+        slots = rcu_dereference(kvm->memslots);
         for (i = 0; i < KVM_MEMORY_SLOTS; ++i) {
-                struct kvm_memory_slot *m = &vcpu->kvm->memslots->memslots[i];
+                struct kvm_memory_slot *m = &slots->memslots[i];
                 struct kvm_rmap_desc *d;
 
                 for (j = 0; j < m->npages; ++j) {
@@ -3319,6 +3318,7 @@ static int count_rmaps(struct kvm_vcpu *vcpu)
                         }
                 }
         }
+        srcu_read_unlock(&kvm->srcu, idx);
         return nmaps;
 }
 
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 18698799e365..f1cae7d6113d 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -1503,7 +1503,11 @@ static void enter_pmode(struct kvm_vcpu *vcpu)
 static gva_t rmode_tss_base(struct kvm *kvm)
 {
         if (!kvm->arch.tss_addr) {
-                gfn_t base_gfn = kvm->memslots->memslots[0].base_gfn +
+                struct kvm_memslots *slots;
+                gfn_t base_gfn;
+
+                slots = rcu_dereference(kvm->memslots);
+                base_gfn = kvm->memslots->memslots[0].base_gfn +
                                  kvm->memslots->memslots[0].npages - 3;
                 return base_gfn << PAGE_SHIFT;
         }