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([2a01:e0a:59e:9d80:527b:9dff:feef:3874]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-38bf321503fsm12721334f8f.12.2025.01.20.23.15.31 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 20 Jan 2025 23:15:32 -0800 (PST) Message-ID: <6289de17-a462-4186-a898-064c15f508a3@redhat.com> Date: Tue, 21 Jan 2025 08:15:30 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] hw/virtio/vhost: Disable IOTLB callbacks when IOMMU gets disabled Content-Language: en-US To: Jason Wang Cc: eric.auger.pro@gmail.com, qemu-devel@nongnu.org, mst@redhat.com, sgarzare@redhat.com, lvivier@redhat.com, zhenzhong.duan@intel.com References: <20250120173339.865681-1-eric.auger@redhat.com> From: Eric Auger In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=170.10.129.124; envelope-from=eric.auger@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -50 X-Spam_score: -5.1 X-Spam_bar: ----- X-Spam_report: (-5.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-3, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham 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: eric.auger@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Hi Jason, On 1/21/25 4:27 AM, Jason Wang wrote: > On Tue, Jan 21, 2025 at 1:33 AM Eric Auger wrote: >> When a guest exposed with a vhost device and protected by an >> intel IOMMU gets rebooted, we sometimes observe a spurious warning: >> >> Fail to lookup the translated address ffffe000 >> >> We observe that the IOMMU gets disabled through a write to the global >> command register (CMAR_GCMD.TE) before the vhost device gets stopped. >> When this warning happens it can be observed an inflight IOTLB >> miss occurs after the IOMMU disable and before the vhost stop. In >> that case a flat translation occurs and the check in >> vhost_memory_region_lookup() fails. >> >> Let's disable the IOTLB callbacks when all IOMMU MRs have been >> unregistered. >> >> Signed-off-by: Eric Auger >> --- >> hw/virtio/vhost.c | 4 ++++ >> 1 file changed, 4 insertions(+) >> >> diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c >> index 6aa72fd434..128c2ab094 100644 >> --- a/hw/virtio/vhost.c >> +++ b/hw/virtio/vhost.c >> @@ -931,6 +931,10 @@ static void vhost_iommu_region_del(MemoryListener *listener, >> break; >> } >> } >> + if (QLIST_EMPTY(&dev->iommu_list) && >> + dev->vhost_ops->vhost_set_iotlb_callback) { >> + dev->vhost_ops->vhost_set_iotlb_callback(dev, false); >> + } > So the current code assumes: > > 1) IOMMU is enabled before vhost starts > 2) IOMMU is disabled after vhost stops > > This patch seems to fix 2) but not 1). Do we need to deal with the > IOMMU enabled after vhost starts? This patch handles the case where the IOMMU is disabled *before* vhost stops (not 2). This is what I concretely observe on guest reboot. But maybe I misunderstood your comments/questions? Thanks Eric > > Thanks > >> } >> >> void vhost_toggle_device_iotlb(VirtIODevice *vdev) >> -- >> 2.47.1 >>