svm: Add mutex_lock to protect apic_access_page_done on AMD systems

svm: Add mutex_lock to protect apic_access_page_done on AMD systems

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 <[email protected]>
Signed-off-by: Amadeusz Juskowiak <[email protected]>
Signed-off-by: Julian Stecklina <[email protected]>
Signed-off-by: Suravee Suthikulpanit <[email protected]>
Reviewed-by: Joerg Roedel <[email protected]>
Cc: [email protected]
Signed-off-by: Paolo Bonzini <[email protected]>