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a="91343494" X-IronPort-AV: E=Sophos;i="6.21,325,1763452800"; d="scan'208";a="91343494" X-CSE-ConnectionGUID: qnB+JV63SsW27egT1f2X+A== X-CSE-MsgGUID: lM2uAASkQtuOKUvGkMsnXQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.21,325,1763452800"; d="scan'208";a="218725654" From: Vivek Kasireddy To: qemu-devel@nongnu.org Cc: Vivek Kasireddy , =?UTF-8?q?Marc-Andr=C3=A9=20Lureau?= , =?UTF-8?q?Alex=20Benn=C3=A9e?= , Akihiko Odaki , Dmitry Osipenko , Alex Williamson , =?UTF-8?q?C=C3=A9dric=20Le=20Goater?= Subject: [PATCH v9 02/10] virtio-gpu: Find hva for Guest's DMA addr associated with a ram device Date: Wed, 4 Mar 2026 22:54:33 -0800 Message-ID: <20260305065700.1155146-3-vivek.kasireddy@intel.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260305065700.1155146-1-vivek.kasireddy@intel.com> References: <20260305065700.1155146-1-vivek.kasireddy@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable 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=192.198.163.8; envelope-from=vivek.kasireddy@intel.com; helo=mgamail.intel.com X-Spam_score_int: -22 X-Spam_score: -2.3 X-Spam_bar: -- X-Spam_report: (-2.3 / 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_MED=-2.3, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.703, RCVD_IN_VALIDITY_SAFE_BLOCKED=1.386, 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: 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 @intel.com) X-ZM-MESSAGEID: 1772694018930158500 If the Guest provides a DMA address that is associated with a ram device (such as a VFIO PCI device region and not its system memory), then we can obtain the hva (host virtual address) by invoking address_space_translate() followed by memory_region_get_ram_ptr(). We cannot use dma_memory_map() because for memory regions that do not support direct access, it would create bounce buffers instead of returning the actual hva, which is not desirable here. And, since VFIO device regions are not considered directly accessible (because they are mostly MMIO based), virtio-gpu cannot invoke dma_memory_map() to obtain the hva in this case. Therefore, in order to handle addresses associated with VFIO devices, we need to use the address_space_translate() API to first identify the right memory region and the appropriate offset within that region and then use memory_region_get_ram_ptr() to get the hva. This approach also works for addresses associated with the system memory region. Note that, although we take an explicit reference on the memory region, we would still rely on dma_memory_unmap() to drop that reference when the dma mapping is eventually unmapped. Cc: Marc-Andr=C3=A9 Lureau Cc: Alex Benn=C3=A9e Cc: Akihiko Odaki Cc: Dmitry Osipenko Cc: Alex Williamson Cc: C=C3=A9dric Le Goater Reviewed-by: Akihiko Odaki Signed-off-by: Vivek Kasireddy --- hw/display/virtio-gpu.c | 21 ++++++++++++++++++--- 1 file changed, 18 insertions(+), 3 deletions(-) diff --git a/hw/display/virtio-gpu.c b/hw/display/virtio-gpu.c index f20111fa57..f5c6a7deb9 100644 --- a/hw/display/virtio-gpu.c +++ b/hw/display/virtio-gpu.c @@ -798,6 +798,23 @@ static void virtio_gpu_set_scanout_blob(VirtIOGPU *g, &fb, res, &ss.r, &cmd->error); } =20 +static void *virtio_gpu_dma_memory_map(VirtIOGPU *g, + struct virtio_gpu_ctrl_command *cmd, + uint64_t a, hwaddr *len) +{ + MemoryRegion *mr; + hwaddr xlat; + + mr =3D address_space_translate(VIRTIO_DEVICE(g)->dma_as, a, &xlat, len, + DMA_DIRECTION_TO_DEVICE, + MEMTXATTRS_UNSPECIFIED); + if (memory_region_is_ram(mr)) { + memory_region_ref(mr); + return memory_region_get_ram_ptr(mr) + xlat; + } + return NULL; +} + int virtio_gpu_create_mapping_iov(VirtIOGPU *g, uint32_t nr_entries, uint32_t offset, struct virtio_gpu_ctrl_command *cmd, @@ -839,9 +856,7 @@ int virtio_gpu_create_mapping_iov(VirtIOGPU *g, =20 do { len =3D l; - map =3D dma_memory_map(VIRTIO_DEVICE(g)->dma_as, a, &len, - DMA_DIRECTION_TO_DEVICE, - MEMTXATTRS_UNSPECIFIED); + map =3D virtio_gpu_dma_memory_map(g, cmd, a, &len); if (!map) { qemu_log_mask(LOG_GUEST_ERROR, "%s: failed to map MMIO mem= ory for" " element %d\n", __func__, e); --=20 2.53.0