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>

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 3febb76..d8475a2 100644 (file)
--- 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;
 }