4.9-stable review patch. If anyone has any objections, please let me know.
------------------
From: Wei Wang wawei@amazon.de
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
--- arch/x86/kvm/svm.c | 19 +++++++++++-------- 1 file changed, 11 insertions(+), 8 deletions(-)
--- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -1333,20 +1333,23 @@ static u64 *avic_get_physical_id_entry(s 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)