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Tsirkin" , =?UTF-8?q?C=C3=A9dric=20Le=20Goater?= Subject: [PULL 21/41] docs/devel: Add IOMMUFD nesting documentation Date: Tue, 13 Jan 2026 10:36:17 +0100 Message-ID: <20260113093637.1549214-22-clg@redhat.com> In-Reply-To: <20260113093637.1549214-1-clg@redhat.com> References: <20260113093637.1549214-1-clg@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=170.10.133.124; envelope-from=clg@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 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, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_PASS=-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: qemu development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1768297280510158500 From: Zhenzhong Duan Add documentation about using IOMMUFD backed VFIO device with intel_iommu w= ith x-flts=3Don. Suggested-by: Yi Liu Signed-off-by: Zhenzhong Duan Reviewed-by: Eric Auger Reviewed-by: Yi Liu Reviewed-by: Michael S. Tsirkin Link: https://lore.kernel.org/qemu-devel/20260106061304.314546-20-zhenzhong= .duan@intel.com Signed-off-by: C=C3=A9dric Le Goater --- docs/devel/vfio-iommufd.rst | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/docs/devel/vfio-iommufd.rst b/docs/devel/vfio-iommufd.rst index b37098e1b625d9be0368e53b7492db64828c88c3..2d6e60dce1d38f1de136c3d65f3= c396aef9e0805 100644 --- a/docs/devel/vfio-iommufd.rst +++ b/docs/devel/vfio-iommufd.rst @@ -152,3 +152,20 @@ RAM discarding for mdev. =20 ``vfio-ap`` and ``vfio-ccw`` devices don't have same issue as their backend devices are always mdev and RAM discarding is force enabled. + +Usage with intel_iommu featuring x-flts=3Don +------------------------------------------ + +Only IOMMUFD backed VFIO device is supported when intel_iommu is configured +with x-flts=3Don, for legacy container backed VFIO device, below error sho= ws: + +.. code-block:: none + + qemu-system-x86_64: -device vfio-pci,host=3D0000:02:00.0: vfio 0000:02= :00.0: Failed to set vIOMMU: Need IOMMUFD backend when x-flts=3Don + +VFIO device under PCI bridge is unsupported, use PCIE bridge if necessary, +otherwise below error shows: + +.. code-block:: none + + qemu-system-x86_64: -device vfio-pci,host=3D0000:02:00.0,bus=3Dbridge1= ,iommufd=3Diommufd0: vfio 0000:02:00.0: Failed to set vIOMMU: Host device d= ownstream to a PCI bridge is unsupported when x-flts=3Don --=20 2.52.0