kernel: KVM: x86: Use __try_cmpxchg_user() to update guest PTE A/D bits

In the Linux kernel, the following vulnerability has been resolved: KVM: x86: Use trycmpxchguser to update guest PTE A/D bits Use the recently introduced trycmpxchguser to update guest PTE A/D bits instead of mapping the PTE into kernel address space. The VMPFNMAP path is broken as it assumes tha...