From nobody Tue Feb 10 09:02:04 2026 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1763785297553232.79474198088462; Fri, 21 Nov 2025 20:21:37 -0800 (PST) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1vMdWv-00021Y-Mb; Fri, 21 Nov 2025 21:39:18 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1vMdWl-0001wV-3S; Fri, 21 Nov 2025 21:39:07 -0500 Received: from isrv.corpit.ru ([212.248.84.144]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1vMdVl-00020X-9E; Fri, 21 Nov 2025 21:39:02 -0500 Received: from tsrv.corpit.ru (tsrv.tls.msk.ru [192.168.177.2]) by isrv.corpit.ru (Postfix) with ESMTP id BBACF16C6EF; Fri, 21 Nov 2025 16:51:55 +0300 (MSK) Received: from think4mjt.tls.msk.ru (mjtthink.wg.tls.msk.ru [192.168.177.146]) by tsrv.corpit.ru (Postfix) with ESMTP id 20B0E32198C; Fri, 21 Nov 2025 16:52:04 +0300 (MSK) From: Michael Tokarev To: qemu-devel@nongnu.org Cc: qemu-stable@nongnu.org, peng guo , "Michael S. Tsirkin" , Michael Tokarev Subject: [Stable-10.1.3 23/76] hw/i386/pc: Avoid overlap between CXL window and PCI 64bit BARs in QEMU Date: Fri, 21 Nov 2025 16:51:01 +0300 Message-ID: <20251121135201.1114964-23-mjt@tls.msk.ru> X-Mailer: git-send-email 2.47.3 In-Reply-To: References: MIME-Version: 1.0 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=212.248.84.144; envelope-from=mjt@tls.msk.ru; helo=isrv.corpit.ru X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, T_SPF_HELO_TEMPERROR=0.01, T_SPF_TEMPERROR=0.01 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+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZM-MESSAGEID: 1763785300301018900 Content-Type: text/plain; charset="utf-8" From: peng guo When using a CXL Type 3 device together with a virtio 9p device in QEMU on a physical server, the 9p device fails to initialize properly. The kernel rep= orts the following error: virtio: device uses modern interface but does not have VIRTIO_F_VERSION= _1 9pnet_virtio virtio0: probe with driver 9pnet_virtio failed with error = -22 Further investigation revealed that the 64-bit BAR space assigned to the 9p= net device was overlapped by the memory window allocated for the CXL devices. A= s a result, the kernel could not correctly access the BAR region, causing the virtio device to malfunction. An excerpt from /proc/iomem shows: 480010000-cffffffff : CXL Window 0 480010000-4bfffffff : PCI Bus 0000:00 4c0000000-4c01fffff : PCI Bus 0000:0c 4c0000000-4c01fffff : PCI Bus 0000:0d 4c0200000-cffffffff : PCI Bus 0000:00 4c0200000-4c0203fff : 0000:00:03.0 4c0200000-4c0203fff : virtio-pci-modern To address this issue, this patch adds the reserved memory end calculation for cxl devices to reserve sufficient address space and ensure that CXL mem= ory windows are allocated beyond all PCI 64-bit BARs. This prevents overlap with 64-bit BARs regions such as those used by virtio or other pcie devices, resolving the conflict. QEMU Build Configuration: ./configure --prefix=3D/home/work/qemu_master/build/ \ --target-list=3Dx86_64-softmmu \ --enable-kvm \ --enable-virtfs QEMU Boot Command: sudo /home/work/qemu_master/qemu/build/qemu-system-x86_64 \ -nographic -machine q35,cxl=3Don -enable-kvm -m 16G -smp 8 \ -hda /home/work/gp_qemu/rootfs.img \ -virtfs local,path=3D/home/work/gp_qemu/share,mount_tag=3Dhost0,sec= urity_model=3Dpassthrough,id=3Dhost0 \ -kernel /home/work/linux_output/arch/x86/boot/bzImage \ --append "console=3DttyS0 crashkernel=3D256M root=3D/dev/sda rootfs= type=3Dext4 rw loglevel=3D8" \ -object memory-backend-ram,id=3Dvmem0,share=3Don,size=3D4096M \ -device pxb-cxl,bus_nr=3D12,bus=3Dpcie.0,id=3Dcxl.1 \ -device cxl-rp,port=3D0,bus=3Dcxl.1,id=3Droot_port13,chassis=3D0,sl= ot=3D2 \ -device cxl-type3,bus=3Droot_port13,volatile-memdev=3Dvmem0,id=3Dcx= l-vmem0,sn=3D0x123456789 \ -M cxl-fmw.0.targets.0=3Dcxl.1,cxl-fmw.0.size=3D4G Fixes: 03b39fcf64bc ("hw/cxl: Make the CXL fixed memory window setup a mach= ine parameter") Signed-off-by: peng guo Reviewed-by: Michael S. Tsirkin Message-ID: <20250805142300.15226-1-engguopeng@buaa.edu.cn> Signed-off-by: Michael S. Tsirkin (cherry picked from commit d1193481dee63442fc41e47ca6ebc4cd34f1f69c) Signed-off-by: Michael Tokarev diff --git a/hw/i386/pc.c b/hw/i386/pc.c index 0861e329b5..1bdd3a6e56 100644 --- a/hw/i386/pc.c +++ b/hw/i386/pc.c @@ -836,6 +836,7 @@ void pc_memory_init(PCMachineState *pcms, hwaddr maxphysaddr, maxusedaddr; hwaddr cxl_base, cxl_resv_end =3D 0; X86CPU *cpu =3D X86_CPU(first_cpu); + uint64_t res_mem_end; =20 assert(machine->ram_size =3D=3D x86ms->below_4g_mem_size + x86ms->above_4g_mem_size); @@ -977,16 +978,17 @@ void pc_memory_init(PCMachineState *pcms, =20 rom_set_fw(fw_cfg); =20 - if (machine->device_memory) { - uint64_t *val =3D g_malloc(sizeof(*val)); - uint64_t res_mem_end; + if (pcms->cxl_devices_state.is_enabled) { + res_mem_end =3D cxl_resv_end; + } else if (machine->device_memory) { + res_mem_end =3D machine->device_memory->base + + memory_region_size(&machine->device_memory->mr); + } else { + res_mem_end =3D 0; + } =20 - if (pcms->cxl_devices_state.is_enabled) { - res_mem_end =3D cxl_resv_end; - } else { - res_mem_end =3D machine->device_memory->base - + memory_region_size(&machine->device_memory->mr= ); - } + if (res_mem_end) { + uint64_t *val =3D g_malloc(sizeof(*val)); *val =3D cpu_to_le64(ROUND_UP(res_mem_end, 1 * GiB)); fw_cfg_add_file(fw_cfg, "etc/reserved-memory-end", val, sizeof(*va= l)); } --=20 2.47.3