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[80.230.48.7]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-48e6fff9c91sm182612165e9.1.2026.05.11.02.09.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 11 May 2026 02:09:38 -0700 (PDT) Date: Mon, 11 May 2026 05:09:35 -0400 From: "Michael S. Tsirkin" To: Tushar Dave Cc: qemu-devel@nongnu.org, alwilliamson@nvidia.com, jgg@nvidia.com, skolothumtho@nvidia.com, qemu-arm@nongnu.org, peter.maydell@linaro.org, marcel.apfelbaum@gmail.com, devel@edk2.groups.io Subject: Re: [RFC PATCH 0/8] hw/arm/virt, hw/pci: PCI pre-enumeration and fixed BAR allocation Message-ID: <20260511050459-mutt-send-email-mst@kernel.org> References: <20260508183717.193630-1-tdave@nvidia.com> MIME-Version: 1.0 In-Reply-To: <20260508183717.193630-1-tdave@nvidia.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: mK_U5PV2oYt69dW1obf1t7QaYZNf9zrlfPHBRaKnq84_1778490579 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=170.10.129.124; envelope-from=mst@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -24 X-Spam_score: -2.5 X-Spam_bar: -- X-Spam_report: (-2.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.445, 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_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-arm@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-arm-bounces+qemu-arm=archiver.kernel.org@nongnu.org Sender: qemu-arm-bounces+qemu-arm=archiver.kernel.org@nongnu.org On Fri, May 08, 2026 at 01:37:09PM -0500, Tushar Dave wrote: > This RFC introduces a mechanism to specify Guest Physical Addresses > (GPAs) for PCI BARs, allowing explicit placement of guest MMIO BAR > addresses to match host physical addresses for assigned devices. > > On some platforms, P2P DMA is performed between devices within the same > IOMMU group. The PCI fabric ACS is configured to permit direct P2P > without going through the host bridge in order to achieve the required > performance. Pass this info to guest firmware, let it set bars any way it wants?