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Mon, 04 Aug 2025 22:24:25 +0800 (CST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=buaa.edu.cn; s=buaa; h=Received:From:To:Cc:Subject:Date: Message-ID:MIME-Version:Content-Transfer-Encoding; bh=2dHtnOao28 utMIUD3/E7Yuhocp6VjBZ5enxgcQtoGf0=; b=n5PwrludH/D5jVUcTstcc/sdz7 RxRTuBsgmW/cSElfW95e+kLqqhPxLvKmYJAbjESgpBPU9O+IkWMt1Cz4FybQnS8G 0xHkwVkf7Iwy9/YKjF65Z+FNZ9NQZDtDCUC4IBjSj1Ne0oZA9gCh3qyakNO9BiZM RkCj1q5bgm2mfoKrI= To: mst@redhat.com, marcel.apfelbaum@gmail.com, pbonzini@redhat.com, richard.henderson@linaro.org, eduardo@habkost.net, qemu-devel@nongnu.org Cc: wyguopeng@163.com, Jonathan.Cameron@huawei.com, peng guo Subject: [PATCH v2] hw/i386/pc: Avoid overlap between CXL window and PCI 64bit BARs in QEMU Date: Mon, 4 Aug 2025 22:24:21 +0800 Message-ID: <20250804142421.153126-1-engguopeng@buaa.edu.cn> X-Mailer: git-send-email 2.43.0 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-CM-TRANSID: Nyz+CgCXX2SXwpBogsslAA--.45796S2 X-Coremail-Antispam: 1UD129KBjvJXoWxZF1DCF4DGrWktry8ArW7twb_yoW5Kr1UpF 93JFy5GF4rKF1xGrn7Zayv93W8GF4vk3W7CF92kw1v9FnxGrn8A34vy34Yv348Zrs3XF17 XF98JF95tw1DuaUanT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUkF1xkIjI8I6I8E6xAIw20EY4v20xvaj40_Wr0E3s1l1IIY67AE w4v_Jr0_Jr4l8cAvFVAK0II2c7xJM28CjxkF64kEwVA0rcxSw2x7M28EF7xvwVC0I7IYx2 IY67AKxVW7JVWDJwA2z4x0Y4vE2Ix0cI8IcVCY1x0267AKxVWxJVW8Jr1l84ACjcxK6I8E 87Iv67AKxVW0oVCq3wA2z4x0Y4vEx4A2jsIEc7CjxVAFwI0_GcCE3s1le2I262IYc4CY6c 8Ij28IcVAaY2xG8wAqx4xG64xvF2IEw4CE5I8CrVC2j2WlYx0E2Ix0cI8IcVAFwI0_Jr0_ Jr4lYx0Ex4A2jsIE14v26r1j6r4UMcvjeVCFs4IE7xkEbVWUJVW8JwACjcxG0xvY0x0EwI xGrwACjI8F5VA0II8E6IAqYI8I648v4I1l42xK82IYc2Ij64vIr41l42xK82IY6x8ErcxF aVAv8VW7tr1UJr1l4I8I3I0E4IkC6x0Yz7v_Jr0_Gr1lx2IqxVAqx4xG67AKxVWUJVWUGw C20s026x8GjcxK67AKxVWUGVWUWwC2zVAF1VAY17CE14v26r1q6r43MIIYrxkI7VAKI48J MIIF0xvE2Ix0cI8IcVAFwI0_Jr0_JF4lIxAIcVC0I7IYx2IY6xkF7I0E14v26r1j6r4UMI IF0xvE42xK8VAvwI8IcIk0rVWUJVWUCwCI42IY6I8E87Iv67AKxVWUJVW8JwCI42IY6I8E 87Iv6xkF7I0E14v26r1j6r4UYxBIdaVFxhVjvjDU0xZFpf9x0JUdHUDUUUUU= X-CM-SenderInfo: d2isijirrujqpexdthxhgxhubq/ 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=13.76.142.27; envelope-from=engguopeng@buaa.edu.cn; helo=azure-sdnproxy.icoremail.net X-Spam_score_int: -16 X-Spam_score: -1.7 X-Spam_bar: - X-Spam_report: (-1.7 / 5.0 requ) BAYES_00=-1.9, DKIM_INVALID=0.1, DKIM_SIGNED=0.1, RCVD_IN_MSPIKE_H2=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=no 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: , Reply-to: peng guo From: peng guo via Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZM-MESSAGEID: 1754323133872116600 Content-Type: text/plain; charset="utf-8" When using a CXL Type 3 device together with a virtio 9p device in QEMU on = a=20 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 =20 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. =20 An excerpt from /proc/iomem shows: =20 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=20 for cxl devices to reserve sufficient address space and ensure that CXL mem= ory=20 windows are allocated beyond all PCI 64-bit BARs. This prevents overlap wit= h=20 64-bit BARs regions such as those used by virtio or other pcie devices,=20 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 --- v1 -> v2: Make the patch clearer and add fixes hw/i386/pc.c | 18 +++++++++--------- 1 file changed, 9 insertions(+), 9 deletions(-) diff --git a/hw/i386/pc.c b/hw/i386/pc.c index 2f58e73d3347..0f10f6edd23e 100644 --- a/hw/i386/pc.c +++ b/hw/i386/pc.c @@ -975,16 +975,16 @@ 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; + uint64_t res_mem_end =3D 0; + 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); + } =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 2.43.0