KVM: use the correct RCU API for PROVE_RCU=y

The RCU/SRCU API have already changed for proving RCU usage.

I got the following dmesg when PROVE_RCU=y because we used incorrect API.
This patch coverts rcu_deference() to srcu_dereference() or family API.

===================================================
[ INFO: suspicious rcu_dereference_check() usage. ]
---------------------------------------------------
arch/x86/kvm/mmu.c:3020 invoked rcu_dereference_check() without protection!

other info that might help us debug this:

rcu_scheduler_active = 1, debug_locks = 0
2 locks held by qemu-system-x86/8550:
 #0:  (&kvm->slots_lock){+.+.+.}, at: [<ffffffffa011a6ac>] kvm_set_memory_region+0x29/0x50 [kvm]
 #1:  (&(&kvm->mmu_lock)->rlock){+.+...}, at: [<ffffffffa012262d>] kvm_arch_commit_memory_region+0xa6/0xe2 [kvm]

stack backtrace:
Pid: 8550, comm: qemu-system-x86 Not tainted 2.6.34-rc4-tip-01028-g939eab1 #27
Call Trace:
 [<ffffffff8106c59e>] lockdep_rcu_dereference+0xaa/0xb3
 [<ffffffffa012f6c1>] kvm_mmu_calculate_mmu_pages+0x44/0x7d [kvm]
 [<ffffffffa012263e>] kvm_arch_commit_memory_region+0xb7/0xe2 [kvm]
 [<ffffffffa011a5d7>] __kvm_set_memory_region+0x636/0x6e2 [kvm]
 [<ffffffffa011a6ba>] kvm_set_memory_region+0x37/0x50 [kvm]
 [<ffffffffa015e956>] vmx_set_tss_addr+0x46/0x5a [kvm_intel]
 [<ffffffffa0126592>] kvm_arch_vm_ioctl+0x17a/0xcf8 [kvm]
 [<ffffffff810a8692>] ? unlock_page+0x27/0x2c
 [<ffffffff810bf879>] ? __do_fault+0x3a9/0x3e1
 [<ffffffffa011b12f>] kvm_vm_ioctl+0x364/0x38d [kvm]
 [<ffffffff81060cfa>] ? up_read+0x23/0x3d
 [<ffffffff810f3587>] vfs_ioctl+0x32/0xa6
 [<ffffffff810f3b19>] do_vfs_ioctl+0x495/0x4db
 [<ffffffff810e6b2f>] ? fget_light+0xc2/0x241
 [<ffffffff810e416c>] ? do_sys_open+0x104/0x116
 [<ffffffff81382d6d>] ? retint_swapgs+0xe/0x13
 [<ffffffff810f3ba6>] sys_ioctl+0x47/0x6a
 [<ffffffff810021db>] system_call_fastpath+0x16/0x1b

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

4 files changed, 14 insertions, 6 deletions

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 7a17db1cdcd6..0682a393ad90 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -787,7 +787,7 @@ static int kvm_handle_hva(struct kvm *kvm, unsigned long hva,
         int retval = 0;
         struct kvm_memslots *slots;
 
-        slots = rcu_dereference(kvm->memslots);
+        slots = kvm_memslots(kvm);
 
         for (i = 0; i < slots->nmemslots; i++) {
                 struct kvm_memory_slot *memslot = &slots->memslots[i];
@@ -3016,7 +3016,8 @@ unsigned int kvm_mmu_calculate_mmu_pages(struct kvm *kvm)
         unsigned int  nr_pages = 0;
         struct kvm_memslots *slots;
 
-        slots = rcu_dereference(kvm->memslots);
+        slots = kvm_memslots(kvm);
+
         for (i = 0; i < slots->nmemslots; i++)
                 nr_pages += slots->memslots[i].npages;
 
@@ -3292,7 +3293,7 @@ static int count_rmaps(struct kvm_vcpu *vcpu)
         int i, j, k, idx;
 
         idx = srcu_read_lock(&kvm->srcu);
-        slots = rcu_dereference(kvm->memslots);
+        slots = kvm_memslots(kvm);
         for (i = 0; i < KVM_MEMORY_SLOTS; ++i) {
                 struct kvm_memory_slot *m = &slots->memslots[i];
                 struct kvm_rmap_desc *d;
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 0b896ac7e4bb..d0a10b5612e9 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -1558,7 +1558,7 @@ static gva_t rmode_tss_base(struct kvm *kvm)
                 struct kvm_memslots *slots;
                 gfn_t base_gfn;
 
-                slots = rcu_dereference(kvm->memslots);
+                slots = kvm_memslots(kvm);
                 base_gfn = kvm->memslots->memslots[0].base_gfn +
                                  kvm->memslots->memslots[0].npages - 3;
                 return base_gfn << PAGE_SHIFT;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 58a96e6a234c..638248c96999 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2497,7 +2497,7 @@ gfn_t unalias_gfn_instantiation(struct kvm *kvm, gfn_t gfn)
         struct kvm_mem_alias *alias;
         struct kvm_mem_aliases *aliases;
 
-        aliases = rcu_dereference(kvm->arch.aliases);
+        aliases = kvm_aliases(kvm);
 
         for (i = 0; i < aliases->naliases; ++i) {
                 alias = &aliases->aliases[i];
@@ -2516,7 +2516,7 @@ gfn_t unalias_gfn(struct kvm *kvm, gfn_t gfn)
         struct kvm_mem_alias *alias;
         struct kvm_mem_aliases *aliases;
 
-        aliases = rcu_dereference(kvm->arch.aliases);
+        aliases = kvm_aliases(kvm);
 
         for (i = 0; i < aliases->naliases; ++i) {
                 alias = &aliases->aliases[i];
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index b7a404722d2b..f4b54458285b 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -65,6 +65,13 @@ static inline int is_paging(struct kvm_vcpu *vcpu)
         return kvm_read_cr0_bits(vcpu, X86_CR0_PG);
 }
 
+static inline struct kvm_mem_aliases *kvm_aliases(struct kvm *kvm)
+{
+        return rcu_dereference_check(kvm->arch.aliases,
+                        srcu_read_lock_held(&kvm->srcu)
+                        || lockdep_is_held(&kvm->slots_lock));
+}
+
 void kvm_before_handle_nmi(struct kvm_vcpu *vcpu);
 void kvm_after_handle_nmi(struct kvm_vcpu *vcpu);