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Tue, 21 Feb 2023 23:44:24 +0000 (UTC) Received: from [10.72.12.31] (ovpn-12-31.pek2.redhat.com [10.72.12.31]) by smtp.corp.redhat.com (Postfix) with ESMTPS id B45EA140EBF4; Tue, 21 Feb 2023 23:44:13 +0000 (UTC) Subject: Re: [PATCH v1 3/6] kvm: Synchronize the backup bitmap in the last stage To: Peter Xu Cc: qemu-arm@nongnu.org, qemu-devel@nongnu.org, pbonzini@redhat.com, peter.maydell@linaro.org, david@redhat.com, philmd@linaro.org, mst@redhat.com, cohuck@redhat.com, quintela@redhat.com, dgilbert@redhat.com, maz@kernel.org, zhenyzha@redhat.com, shan.gavin@gmail.com References: <20230213003925.40158-1-gshan@redhat.com> <20230213003925.40158-4-gshan@redhat.com> From: Gavin Shan Message-ID: <08c954d7-f4e4-4d63-28fc-50128f4bc2d7@redhat.com> Date: Wed, 22 Feb 2023 10:44:07 +1100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 3.1 on 10.11.54.7 Received-SPF: pass client-ip=170.10.133.124; envelope-from=gshan@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.095, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Gavin Shan Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 2/22/23 4:46 AM, Peter Xu wrote: > On Mon, Feb 13, 2023 at 08:39:22AM +0800, Gavin Shan wrote: >> In the last stage of live migration or memory slot removal, the >> backup bitmap needs to be synchronized when it has been enabled. >> >> Signed-off-by: Gavin Shan >> --- >> accel/kvm/kvm-all.c | 11 +++++++++++ >> include/sysemu/kvm_int.h | 1 + >> 2 files changed, 12 insertions(+) >> >> diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c >> index 01a6a026af..b5e12de522 100644 >> --- a/accel/kvm/kvm-all.c >> +++ b/accel/kvm/kvm-all.c >> @@ -1352,6 +1352,10 @@ static void kvm_set_phys_mem(KVMMemoryListener *kml, >> */ >> if (kvm_state->kvm_dirty_ring_size) { >> kvm_dirty_ring_reap_locked(kvm_state, NULL); >> + if (kvm_state->kvm_dirty_ring_with_bitmap) { >> + kvm_slot_sync_dirty_pages(mem); >> + kvm_slot_get_dirty_log(kvm_state, mem); >> + } >> } else { >> kvm_slot_get_dirty_log(kvm_state, mem); >> } > > IIUC after the memory atomic update changes lands QEMU, we may not need > this sync at all. > > My understanding is that we sync dirty log here only because of non-atomic > updates happening in the past and we may lose dirty bits unexpectedly. > Maybe Paolo knows. > > But that needs some more justification and history digging, so definitely > more suitable to leave it for later and separate discussion. > > Reviewed-by: Peter Xu > Peter, could you please give some hints for me to understand the atomic and non-atomic update here? Ok, I will drop this part of changes in next revision with the assumption that we have atomic update supported for ARM64. Thanks, Gavin > >> @@ -1573,6 +1577,12 @@ static void kvm_log_sync_global(MemoryListener *l, bool last_stage) >> mem = &kml->slots[i]; >> if (mem->memory_size && mem->flags & KVM_MEM_LOG_DIRTY_PAGES) { >> kvm_slot_sync_dirty_pages(mem); >> + >> + if (s->kvm_dirty_ring_with_bitmap && last_stage && >> + kvm_slot_get_dirty_log(s, mem)) { >> + kvm_slot_sync_dirty_pages(mem); >> + } >> + >> /* >> * This is not needed by KVM_GET_DIRTY_LOG because the >> * ioctl will unconditionally overwrite the whole region. >> @@ -3701,6 +3711,7 @@ static void kvm_accel_instance_init(Object *obj) >> s->kernel_irqchip_split = ON_OFF_AUTO_AUTO; >> /* KVM dirty ring is by default off */ >> s->kvm_dirty_ring_size = 0; >> + s->kvm_dirty_ring_with_bitmap = false; >> s->notify_vmexit = NOTIFY_VMEXIT_OPTION_RUN; >> s->notify_window = 0; >> } >> diff --git a/include/sysemu/kvm_int.h b/include/sysemu/kvm_int.h >> index 60b520a13e..fdd5b1bde0 100644 >> --- a/include/sysemu/kvm_int.h >> +++ b/include/sysemu/kvm_int.h >> @@ -115,6 +115,7 @@ struct KVMState >> } *as; >> uint64_t kvm_dirty_ring_bytes; /* Size of the per-vcpu dirty ring */ >> uint32_t kvm_dirty_ring_size; /* Number of dirty GFNs per ring */ >> + bool kvm_dirty_ring_with_bitmap; >> struct KVMDirtyRingReaper reaper; >> NotifyVmexitOption notify_vmexit; >> uint32_t notify_window; >> -- >> 2.23.0 >> >