svm: Add mutex_lock to protect apic_access_page_done on AMD systems

commit 30510387a5e45bfcf8190e03ec7aa15b295828e2 upstream.

There is a race condition when accessing kvm->arch.apic_access_page_done.
Due to it, x86_set_memory_region will fail when creating the second vcpu
for a svm guest.

Add a mutex_lock to serialize the accesses to apic_access_page_done.
This lock is also used by vmx for the same purpose.

Signed-off-by: Wei Wang <wawei@amazon.de>
Signed-off-by: Amadeusz Juskowiak <ajusk@amazon.de>
Signed-off-by: Julian Stecklina <jsteckli@amazon.de>
Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Reviewed-by: Joerg Roedel <jroedel@suse.de>
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 17f08db..4dc79d1 100644 (file)
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1399,20 +1399,23 @@ static u64 *avic_get_physical_id_entry(struct kvm_vcpu *vcpu,
 static int avic_init_access_page(struct kvm_vcpu *vcpu)
 {
        struct kvm *kvm = vcpu->kvm;
-       int ret;
+       int ret = 0;
 
+       mutex_lock(&kvm->slots_lock);
        if (kvm->arch.apic_access_page_done)
-               return 0;
+               goto out;
 
-       ret = x86_set_memory_region(kvm,
-                                   APIC_ACCESS_PAGE_PRIVATE_MEMSLOT,
-                                   APIC_DEFAULT_PHYS_BASE,
-                                   PAGE_SIZE);
+       ret = __x86_set_memory_region(kvm,
+                                     APIC_ACCESS_PAGE_PRIVATE_MEMSLOT,
+                                     APIC_DEFAULT_PHYS_BASE,
+                                     PAGE_SIZE);
        if (ret)
-               return ret;
+               goto out;
 
        kvm->arch.apic_access_page_done = true;
-       return 0;
+out:
+       mutex_unlock(&kvm->slots_lock);
+       return ret;
 }
 
 static int avic_init_backing_page(struct kvm_vcpu *vcpu)