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Thu, 11 Dec 2025 00:23:08 -0800 (PST) MIME-Version: 1.0 References: <20251117093729.1121324-1-zhenzhong.duan@intel.com> <20251117093729.1121324-3-zhenzhong.duan@intel.com> In-Reply-To: <20251117093729.1121324-3-zhenzhong.duan@intel.com> From: Jason Wang Date: Thu, 11 Dec 2025 16:22:54 +0800 X-Gm-Features: AQt7F2rI7HQ3UX34cen4_J4RCup3w7aO4yj0ZrWsmaHEKQL2X0QiTRqEjCAGLR4 Message-ID: Subject: Re: [PATCH v8 02/23] intel_iommu: Delete RPS capability related supporting code To: Zhenzhong Duan Cc: qemu-devel@nongnu.org, alex@shazbot.org, clg@redhat.com, eric.auger@redhat.com, mst@redhat.com, peterx@redhat.com, ddutile@redhat.com, jgg@nvidia.com, nicolinc@nvidia.com, skolothumtho@nvidia.com, joao.m.martins@oracle.com, clement.mathieu--drif@eviden.com, kevin.tian@intel.com, yi.l.liu@intel.com, chao.p.peng@intel.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Received-SPF: pass client-ip=170.10.129.124; envelope-from=jasowang@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_H2=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: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Mon, Nov 17, 2025 at 5:38=E2=80=AFPM Zhenzhong Duan wrote: > > RID-PASID Support(RPS) is not set in vIOMMU ECAP register, the supporting > code is there but never takes effect. > > Meanwhile, according to VTD spec section 3.4.3: > "Implementations not supporting RID_PASID capability (ECAP_REG.RPS is 0b)= , > use a PASID value of 0 to perform address translation for requests withou= t > PASID." > > We should delete the supporting code which fetches RID_PASID field from > scalable context entry and use 0 as RID_PASID directly, because RID_PASID > field is ignored if no RPS support according to spec. > > This simplifies the code and doesn't bring any penalty. > > Suggested-by: Yi Liu > Signed-off-by: Zhenzhong Duan > --- Is the feature deprecated in the spec? If not, it should be still better to enable it. Thanks