Vitaly Kuznetsov 1ebfaa11eb KVM: x86: Wait for IPIs to be delivered when handling Hyper-V TLB flush hypercall ... Prior to commit 0baedd7927 ("KVM: x86: make Hyper-V PV TLB flush use tlb_flush_guest()"), kvm_hv_flush_tlb() was using 'KVM_REQ_TLB_FLUSH | KVM_REQUEST_NO_WAKEUP' when making a request to flush TLBs on other vCPUs and KVM_REQ_TLB_FLUSH is/was defined as: (0 | KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP) so KVM_REQUEST_WAIT was lost. Hyper-V TLFS, however, requires that "This call guarantees that by the time control returns back to the caller, the observable effects of all flushes on the specified virtual processors have occurred." and without KVM_REQUEST_WAIT there's a small chance that the vCPU making the TLB flush will resume running before all IPIs get delivered to other vCPUs and a stale mapping can get read there. Fix the issue by adding KVM_REQUEST_WAIT flag to KVM_REQ_TLB_FLUSH_GUEST: kvm_hv_flush_tlb() is the sole caller which uses it for kvm_make_all_cpus_request()/kvm_make_vcpus_request_mask() where KVM_REQUEST_WAIT makes a difference. Cc: stable@kernel.org Fixes: 0baedd7927 ("KVM: x86: make Hyper-V PV TLB flush use tlb_flush_guest()") Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com> Message-Id: <20211209102937.584397-1-vkuznets@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>		2021-12-10 07:12:41 -05:00
..
asm	KVM: x86: Wait for IPIs to be delivered when handling Hyper-V TLB flush hypercall	2021-12-10 07:12:41 -05:00
uapi/asm	Merge branch 'kvm-5.16-fixes' into kvm-master	2021-11-11 11:03:05 -05:00