KVM: fix rcu usage in init_rmode_* functions

fix:
[ 3494.671786] stack backtrace:
[ 3494.671789] Pid: 10527, comm: qemu-system-x86 Not tainted 2.6.38-rc6+ #23
[ 3494.671790] Call Trace:
[ 3494.671796]  [] ? lockdep_rcu_dereference+0x9d/0xa5
[ 3494.671826]  [] ? kvm_memslots+0x6b/0x73 [kvm]
[ 3494.671834]  [] ? gfn_to_memslot+0x16/0x4f [kvm]
[ 3494.671843]  [] ? gfn_to_hva+0x16/0x27 [kvm]
[ 3494.671851]  [] ? kvm_write_guest_page+0x31/0x83 [kvm]
[ 3494.671861]  [] ? kvm_clear_guest_page+0x1a/0x1c [kvm]
[ 3494.671867]  [] ? vmx_set_tss_addr+0x83/0x122 [kvm_intel]

and:
[ 8328.789599] stack backtrace:
[ 8328.789601] Pid: 18736, comm: qemu-system-x86 Not tainted 2.6.38-rc6+ #23
[ 8328.789603] Call Trace:
[ 8328.789609]  [] ? lockdep_rcu_dereference+0x9d/0xa5
[ 8328.789621]  [] ? kvm_memslots+0x6b/0x73 [kvm]
[ 8328.789628]  [] ? gfn_to_memslot+0x16/0x4f [kvm]
[ 8328.789635]  [] ? gfn_to_hva+0x16/0x27 [kvm]
[ 8328.789643]  [] ? kvm_write_guest_page+0x31/0x83 [kvm]
[ 8328.789699]  [] ? kvm_clear_guest_page+0x1a/0x1c [kvm]
[ 8328.789713]  [] ? vmx_create_vcpu+0x316/0x3c8 [kvm_intel]

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 8 insertions, 4 deletions

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 3febb763cb7f..d8475a26add6 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -2397,11 +2397,12 @@ static bool guest_state_valid(struct kvm_vcpu *vcpu)
 
 static int init_rmode_tss(struct kvm *kvm)
 {
-        gfn_t fn = rmode_tss_base(kvm) >> PAGE_SHIFT;
+        gfn_t fn;
         u16 data = 0;
-        int ret = 0;
-        int r;
+        int r, idx, ret = 0;
 
+        idx = srcu_read_lock(&kvm->srcu);
+        fn = rmode_tss_base(kvm) >> PAGE_SHIFT;
         r = kvm_clear_guest_page(kvm, fn, 0, PAGE_SIZE);
         if (r < 0)
                 goto out;
@@ -2425,12 +2426,13 @@ static int init_rmode_tss(struct kvm *kvm)
 
         ret = 1;
 out:
+        srcu_read_unlock(&kvm->srcu, idx);
         return ret;
 }
 
 static int init_rmode_identity_map(struct kvm *kvm)
 {
-        int i, r, ret;
+        int i, idx, r, ret;
         pfn_t identity_map_pfn;
         u32 tmp;
 
@@ -2445,6 +2447,7 @@ static int init_rmode_identity_map(struct kvm *kvm)
                 return 1;
         ret = 0;
         identity_map_pfn = kvm->arch.ept_identity_map_addr >> PAGE_SHIFT;
+        idx = srcu_read_lock(&kvm->srcu);
         r = kvm_clear_guest_page(kvm, identity_map_pfn, 0, PAGE_SIZE);
         if (r < 0)
                 goto out;
@@ -2460,6 +2463,7 @@ static int init_rmode_identity_map(struct kvm *kvm)
         kvm->arch.ept_identity_pagetable_done = true;
         ret = 1;
 out:
+        srcu_read_unlock(&kvm->srcu, idx);
         return ret;
 }