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>

2 files changed, 3 insertions, 6 deletions

diff --git a/include/linux/kvm.h b/include/linux/kvm.h
index a24de0b1858e..f2feef68ffd6 100644
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -103,7 +103,7 @@ struct kvm_userspace_memory_region {
 
 /* for kvm_memory_region::flags */
 #define KVM_MEM_LOG_DIRTY_PAGES  1UL
-
+#define KVM_MEMSLOT_INVALID      (1UL << 1)
 
 /* for KVM_IRQ_LINE */
 struct kvm_irq_level {
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 9af240387fe6..93bd30701ca7 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -162,6 +162,7 @@ struct kvm {
         struct rw_semaphore slots_lock;
         struct mm_struct *mm; /* userspace tied to this vm */
         struct kvm_memslots *memslots;
+        struct srcu_struct srcu;
 #ifdef CONFIG_KVM_APIC_ARCHITECTURE
         u32 bsp_vcpu_id;
         struct kvm_vcpu *bsp_vcpu;
@@ -275,6 +276,7 @@ void kvm_set_page_accessed(struct page *page);
 pfn_t gfn_to_pfn(struct kvm *kvm, gfn_t gfn);
 pfn_t gfn_to_pfn_memslot(struct kvm *kvm,
                          struct kvm_memory_slot *slot, gfn_t gfn);
+int memslot_id(struct kvm *kvm, gfn_t gfn);
 void kvm_release_pfn_dirty(pfn_t);
 void kvm_release_pfn_clean(pfn_t pfn);
 void kvm_set_pfn_dirty(pfn_t pfn);
@@ -490,11 +492,6 @@ static inline void kvm_guest_exit(void)
         current->flags &= ~PF_VCPU;
 }
 
-static inline int memslot_id(struct kvm *kvm, struct kvm_memory_slot *slot)
-{
-        return slot - kvm->memslots->memslots;
-}
-
 static inline gpa_t gfn_to_gpa(gfn_t gfn)
 {
         return (gpa_t)gfn << PAGE_SHIFT;