kvm: Remove ept_identity_pagetable from struct kvm_arch.

kvm_arch->ept_identity_pagetable holds the ept identity pagetable page. But
it is never used to refer to the page at all.

In vcpu initialization, it indicates two things:
1. indicates if ept page is allocated
2. indicates if a memory slot for identity page is initialized

Actually, kvm_arch->ept_identity_pagetable_done is enough to tell if the ept
identity pagetable is initialized. So we can remove ept_identity_pagetable.

NOTE: In the original code, ept identity pagetable page is pinned in memroy.
      As a result, it cannot be migrated/hot-removed. After this patch, since
      kvm_arch->ept_identity_pagetable is removed, ept identity pagetable page
      is no longer pinned in memory. And it can be migrated/hot-removed.

Signed-off-by: Tang Chen <tangchen@cn.fujitsu.com>
Reviewed-by: Gleb Natapov <gleb@kernel.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 2dbde3b..028df8d 100644 (file)
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -578,7 +578,6 @@ struct kvm_arch {
 
        gpa_t wall_clock;
 
-       struct page *ept_identity_pagetable;
        bool ept_identity_pagetable_done;
        gpa_t ept_identity_map_addr;
 

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 5db47db..5de0d7b 100644 (file)
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -767,6 +767,7 @@ static u32 vmx_segment_access_rights(struct kvm_segment *var);
 static void vmx_sync_pir_to_irr_dummy(struct kvm_vcpu *vcpu);
 static void copy_vmcs12_to_shadow(struct vcpu_vmx *vmx);
 static void copy_shadow_to_vmcs12(struct vcpu_vmx *vmx);
+static int alloc_identity_pagetable(struct kvm *kvm);
 
 static DEFINE_PER_CPU(struct vmcs *, vmxarea);
 static DEFINE_PER_CPU(struct vmcs *, current_vmcs);
@@ -3962,21 +3963,27 @@ out:
 
 static int init_rmode_identity_map(struct kvm *kvm)
 {
-       int i, idx, r, ret;
+       int i, idx, r, ret = 0;
        pfn_t identity_map_pfn;
        u32 tmp;
 
        if (!enable_ept)
                return 1;
-       if (unlikely(!kvm->arch.ept_identity_pagetable)) {
-               printk(KERN_ERR "EPT: identity-mapping pagetable "
-                       "haven't been allocated!\n");
-               return 0;
+
+       /* Protect kvm->arch.ept_identity_pagetable_done. */
+       mutex_lock(&kvm->slots_lock);
+
+       if (likely(kvm->arch.ept_identity_pagetable_done)) {
+               ret = 1;
+               goto out2;
        }
-       if (likely(kvm->arch.ept_identity_pagetable_done))
-               return 1;
-       ret = 0;
+
        identity_map_pfn = kvm->arch.ept_identity_map_addr >> PAGE_SHIFT;
+
+       r = alloc_identity_pagetable(kvm);
+       if (r)
+               goto out2;
+
        idx = srcu_read_lock(&kvm->srcu);
        r = kvm_clear_guest_page(kvm, identity_map_pfn, 0, PAGE_SIZE);
        if (r < 0)
@@ -3994,6 +4001,9 @@ static int init_rmode_identity_map(struct kvm *kvm)
        ret = 1;
 out:
        srcu_read_unlock(&kvm->srcu, idx);
+
+out2:
+       mutex_unlock(&kvm->slots_lock);
        return ret;
 }
 
@@ -4043,31 +4053,20 @@ out:
 
 static int alloc_identity_pagetable(struct kvm *kvm)
 {
-       struct page *page;
+       /* Called with kvm->slots_lock held. */
+
        struct kvm_userspace_memory_region kvm_userspace_mem;
        int r = 0;
 
-       mutex_lock(&kvm->slots_lock);
-       if (kvm->arch.ept_identity_pagetable)
-               goto out;
+       BUG_ON(kvm->arch.ept_identity_pagetable_done);
+
        kvm_userspace_mem.slot = IDENTITY_PAGETABLE_PRIVATE_MEMSLOT;
        kvm_userspace_mem.flags = 0;
        kvm_userspace_mem.guest_phys_addr =
                kvm->arch.ept_identity_map_addr;
        kvm_userspace_mem.memory_size = PAGE_SIZE;
        r = __kvm_set_memory_region(kvm, &kvm_userspace_mem);
-       if (r)
-               goto out;
-
-       page = gfn_to_page(kvm, kvm->arch.ept_identity_map_addr >> PAGE_SHIFT);
-       if (is_error_page(page)) {
-               r = -EFAULT;
-               goto out;
-       }
 
-       kvm->arch.ept_identity_pagetable = page;
-out:
-       mutex_unlock(&kvm->slots_lock);
        return r;
 }
 
@@ -7758,8 +7757,6 @@ static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm, unsigned int id)
                        kvm->arch.ept_identity_map_addr =
                                VMX_EPT_IDENTITY_PAGETABLE_ADDR;
                err = -ENOMEM;
-               if (alloc_identity_pagetable(kvm) != 0)
-                       goto free_vmcs;
                if (!init_rmode_identity_map(kvm))
                        goto free_vmcs;
        }

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 68660b3..2d7f65d 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7273,8 +7273,6 @@ void kvm_arch_destroy_vm(struct kvm *kvm)
        kvm_free_vcpus(kvm);
        if (kvm->arch.apic_access_page)
                put_page(kvm->arch.apic_access_page);
-       if (kvm->arch.ept_identity_pagetable)
-               put_page(kvm->arch.ept_identity_pagetable);
        kfree(rcu_dereference_check(kvm->arch.apic_map, 1));
 }