Commits
Sean Christopherson committed a592a3b8fc6
Revert "KVM: MMU: document fast invalidate all pages" Remove x86 KVM's fast invalidate mechanism, i.e. revert all patches from the original series[1]. Though not explicitly stated, for all intents and purposes the fast invalidate mechanism was added to speed up the scenario where removing a memslot, e.g. as part of accessing reading PCI ROM, caused KVM to flush all shadow entries[1]. Now that the memslot case flushes only shadow entries belonging to the memslot, i.e. doesn't use the fast invalidate mechanism, the only remaining usage of the mechanism are when the VM is being destroyed and when the MMIO generation rolls over. When a VM is being destroyed, either there are no active vcpus, i.e. there's no lock contention, or the VM has ungracefully terminated, in which case we want to reclaim its pages as quickly as possible, i.e. not release the MMU lock if there are still CPUs executing in the VM. The MMIO generation scenario is almost literally a one-in-a-million occurrence, i.e. is not a performance sensitive scenario. Given that lock-breaking is not desirable (VM teardown) or irrelevant (MMIO generation overflow), remove the fast invalidate mechanism to simplify the code (a small amount) and to discourage future code from zapping all pages as using such a big hammer should be a last restort. This reverts commit f6f8adeef542a18b1cb26a0b772c9781a10bb477. [1] https://lkml.kernel.org/r/1369960590-14138-1-git-send-email-xiaoguangrong@linux.vnet.ibm.com Cc: Xiao Guangrong <guangrong.xiao@gmail.com> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>