On 03/11/2016 01:07 AM, Paolo Bonzini wrote:
On 09/03/2016 08:18, Lan Tianyu wrote:How about the following comments. Log for kvm_mmu_commit_zap_page() /* * We need to make sure everyone sees our modifications to * the page tables and see changes to vcpu->mode here.Please mention that this pairs with vcpu_enter_guest and walk_shadow_page_lockless_begin/end.The * barrier in the kvm_flush_remote_tlbs() helps us to achieve * these. Otherwise, wait for all vcpus to exit guest mode * and/or lockless shadow page table walks. */ kvm_flush_remote_tlbs(kvm);The rest of the comment is okay, but please replace "Otherwise" with "In addition, we need to".Log for kvm_flush_remote_tlbs() /* * We want to publish modifications to the page tables before * reading mode. Pairs with a memory barrier in arch-specific * code. * - x86: smp_mb__after_srcu_read_unlock in vcpu_enter_guest.... and smp_mb in walk_shadow_page_lockless_begin/end.* - powerpc: smp_mb in kvmppc_prepare_to_enter. */ smp_mb__before_atomic();The comment looks good, but the smp_mb__before_atomic() is not needed. As mentioned in the reply to Guangrong, only a smp_load_acquire is required. So the comment should say something like "There is already an smp_mb() before kvm_make_all_cpus_request reads vcpu->mode. We reuse that barrier here.". On top of this there is: - the change to paging_tmpl.h that Guangrong posted, adding smp_wmb() before each increment of vcpu->kvm->tlbs_dirty
Yes, please make it as a separated patch.
- the change to smp_mb__after_atomic() in kvm_make_all_cpus_request - if you want :) you can also replace the store+mb in walk_shadow_page_lockless_begin with smp_store_mb, and the mb+store in walk_shadow_page_lockless_end with smp_store_release.
These changes are good to me. TianYu, please CC me when you post the new version out.
