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Mon, 16 Jun 2025 17:56:46 -0700 (PDT) Received: from [172.20.10.3] ([58.246.155.248]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2365decb864sm67926375ad.213.2025.06.16.17.56.44 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 16 Jun 2025 17:56:45 -0700 (PDT) Message-ID: <92845463-8315-4ad8-9eab-eb2f4972cbaa@gmail.com> Date: Tue, 17 Jun 2025 08:56:41 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] vfio/pci: Introduce x-pci-class-code option From: Tomita Moeko To: Alex Williamson Cc: =?UTF-8?Q?C=C3=A9dric_Le_Goater?= , qemu-devel@nongnu.org References: <20250528155548.29344-1-tomitamoeko@gmail.com> <20250528123019.5ff938ed.alex.williamson@redhat.com> In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=2607:f8b0:4864:20::643; envelope-from=tomitamoeko@gmail.com; helo=mail-pl1-x643.google.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, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FROM=0.001, RCVD_IN_DNSWL_NONE=-0.0001, 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: 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 2025/5/29 18:41, Tomita Moeko wrote: > On 2025/5/29 2:30, Alex Williamson wrote: >> On Wed, 28 May 2025 23:55:48 +0800 >> Tomita Moeko wrote: >> >>> Introduce x-pci-class-code option to allow users to override PCI class >>> code of a device, similar to the existing x-pci-vendor-id option. Only >>> the lower 24 bits of this option are used, though a uint32 is used here >>> for determining whether the value is valid and set by user. >>> >>> Additionally, to prevent exposing VGA ranges on non-VGA devices, the >>> x-vga=on option requires x-pci-class-code is either unset or set to >>> VGA controller class. >>> >>> This is mainly intended for IGD devices that expose themselves either >>> as VGA controller (primary display) or Display controller (non-primary >>> display). The UEFI GOP driver depends on the device reporting a VGA >>> controller class code (0x030000). >>> >>> Signed-off-by: Tomita Moeko >>> --- >>> v2: >>> * Add vdev class code check in vfio_populate_vga(). >>> * Fix type in trace-events. >>> Link: https://lore.kernel.org/all/20250524153102.19747-1-tomitamoeko@gmail.com/ >>> >>> hw/vfio/pci.c | 25 +++++++++++++++++++++++++ >>> hw/vfio/pci.h | 1 + >>> hw/vfio/trace-events | 1 + >>> 3 files changed, 27 insertions(+) >>> >>> diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c >>> index b1250d85bf..d57cb7356e 100644 >>> --- a/hw/vfio/pci.c >>> +++ b/hw/vfio/pci.c >>> @@ -2726,6 +2726,14 @@ bool vfio_populate_vga(VFIOPCIDevice *vdev, Error **errp) >>> return false; >>> } >>> >>> + /* vdev class should be either unmodified (PCI_ANY_ID), or VGA controller */ >>> + if ((vdev->class_code != PCI_ANY_ID) && >>> + (vdev->class_code != (PCI_CLASS_DISPLAY_VGA << 8)) && >>> + (vdev->class_code != (PCI_CLASS_NOT_DEFINED_VGA << 8))) { >>> + error_setg(errp, "vdev is not a VGA device"); >>> + return false; >>> + } >> >> I think we should follow the scheme used for vendor_id and device_id to >> populate the struct field when not specified. That let's us use it >> more easily and consistently for things like this. > > Hi, Alex > > The class code override takes place in vfio_pci_config_setup(), where > is after vfio_populate_vga() is called in vfio_populate_device(). So > I have to check if it equals to default or VGA class code here, and > not initializing the sturct field with device value. If we decide to > initialize it for other purpose, I personally think we should also > save the subvendor/subdevice value as well. It have been several weeks, wondering if there is further comments. Thanks, Moeko >> I think we can ignore PCI_CLASS_NOT_DEFINED_VGA. The PCI Local Bus >> Specification 2.1, dated June 1, 1995 (earliest I can find on the SIG) >> includes the VGA class code and specifies base class 0x00 is reserved >> for compatibility with devices built before the base class field was >> defined, so at least before 1995. Also, neither the kernel or QEMU >> is_vga helpers account for this, so they'd not have a VGA region or be >> properly detected elsewhere. Thanks, >> >> Alex > > Got it, will remove this in v3. > > Thanks, > Moeko > >>> + >>> if (!(reg_info->flags & VFIO_REGION_INFO_FLAG_READ) || >>> !(reg_info->flags & VFIO_REGION_INFO_FLAG_WRITE) || >>> reg_info->size < 0xbffff + 1) { >>> @@ -3092,6 +3100,21 @@ static bool vfio_pci_config_setup(VFIOPCIDevice *vdev, Error **errp) >>> vdev->sub_device_id); >>> } >>> >>> + /* >>> + * Class code is a 24-bit value at config space 0x09. Allow overriding it >>> + * with any 24-bit value. >>> + */ >>> + if (vdev->class_code != PCI_ANY_ID) { >>> + if (vdev->class_code > 0xffffff) { >>> + error_setg(errp, "invalid PCI class code provided"); >>> + return false; >>> + } >>> + /* Higher 24 bits of PCI_CLASS_REVISION are class code */ >>> + vfio_add_emulated_long(vdev, PCI_CLASS_REVISION, >>> + vdev->class_code << 8, ~0xff); >>> + trace_vfio_pci_emulated_class_code(vbasedev->name, vdev->class_code); >>> + } >>> + >>> /* QEMU can change multi-function devices to single function, or reverse */ >>> vdev->emulated_config_bits[PCI_HEADER_TYPE] = >>> PCI_HEADER_TYPE_MULTI_FUNCTION; >>> @@ -3489,6 +3512,8 @@ static const Property vfio_pci_dev_properties[] = { >>> sub_vendor_id, PCI_ANY_ID), >>> DEFINE_PROP_UINT32("x-pci-sub-device-id", VFIOPCIDevice, >>> sub_device_id, PCI_ANY_ID), >>> + DEFINE_PROP_UINT32("x-pci-class-code", VFIOPCIDevice, >>> + class_code, PCI_ANY_ID), >>> DEFINE_PROP_UINT32("x-igd-gms", VFIOPCIDevice, igd_gms, 0), >>> DEFINE_PROP_UNSIGNED_NODEFAULT("x-nv-gpudirect-clique", VFIOPCIDevice, >>> nv_gpudirect_clique, >>> diff --git a/hw/vfio/pci.h b/hw/vfio/pci.h >>> index 5ce0fb916f..587eb8cc9a 100644 >>> --- a/hw/vfio/pci.h >>> +++ b/hw/vfio/pci.h >>> @@ -156,6 +156,7 @@ struct VFIOPCIDevice { >>> uint32_t device_id; >>> uint32_t sub_vendor_id; >>> uint32_t sub_device_id; >>> + uint32_t class_code; >>> uint32_t features; >>> #define VFIO_FEATURE_ENABLE_VGA_BIT 0 >>> #define VFIO_FEATURE_ENABLE_VGA (1 << VFIO_FEATURE_ENABLE_VGA_BIT) >>> diff --git a/hw/vfio/trace-events b/hw/vfio/trace-events >>> index e90ec9bff8..e8d585b49a 100644 >>> --- a/hw/vfio/trace-events >>> +++ b/hw/vfio/trace-events >>> @@ -46,6 +46,7 @@ vfio_pci_emulated_vendor_id(const char *name, uint16_t val) "%s 0x%04x" >>> vfio_pci_emulated_device_id(const char *name, uint16_t val) "%s 0x%04x" >>> vfio_pci_emulated_sub_vendor_id(const char *name, uint16_t val) "%s 0x%04x" >>> vfio_pci_emulated_sub_device_id(const char *name, uint16_t val) "%s 0x%04x" >>> +vfio_pci_emulated_class_code(const char *name, uint32_t val) "%s 0x%06x" >>> >>> # pci-quirks.c >>> vfio_quirk_rom_in_denylist(const char *name, uint16_t vid, uint16_t did) "%s %04x:%04x" >> >