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Tsirkin" To: Chuck Zmudzinski Cc: qemu-devel@nongnu.org, Stefano Stabellini , Anthony Perard , Paul Durrant , Paolo Bonzini , Richard Henderson , Eduardo Habkost , Marcel Apfelbaum , xen-devel@lists.xenproject.org Subject: Re: [PATCH v8] xen/pt: reserve PCI slot 2 for Intel igd-passthru Message-ID: <20230110030331-mutt-send-email-mst@kernel.org> References: MIME-Version: 1.0 In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Tue, Jan 10, 2023 at 02:08:34AM -0500, Chuck Zmudzinski wrote: > Intel specifies that the Intel IGD must occupy slot 2 on the PCI bus, > as noted in docs/igd-assign.txt in the Qemu source code. > > Currently, when the xl toolstack is used to configure a Xen HVM guest with > Intel IGD passthrough to the guest with the Qemu upstream device model, > a Qemu emulated PCI device will occupy slot 2 and the Intel IGD will occupy > a different slot. This problem often prevents the guest from booting. > > The only available workaround is not good: Configure Xen HVM guests to use > the old and no longer maintained Qemu traditional device model available > from xenbits.xen.org which does reserve slot 2 for the Intel IGD. > > To implement this feature in the Qemu upstream device model for Xen HVM > guests, introduce the following new functions, types, and macros: > > * XEN_PT_DEVICE_CLASS declaration, based on the existing TYPE_XEN_PT_DEVICE > * XEN_PT_DEVICE_GET_CLASS macro helper function for XEN_PT_DEVICE_CLASS > * typedef XenPTQdevRealize function pointer > * XEN_PCI_IGD_SLOT_MASK, the value of slot_reserved_mask to reserve slot 2 > * xen_igd_reserve_slot and xen_igd_clear_slot functions > > The new xen_igd_reserve_slot function uses the existing slot_reserved_mask > member of PCIBus to reserve PCI slot 2 for Xen HVM guests configured using > the xl toolstack with the gfx_passthru option enabled, which sets the > igd-passthru=on option to Qemu for the Xen HVM machine type. > > The new xen_igd_reserve_slot function also needs to be implemented in > hw/xen/xen_pt_stub.c to prevent FTBFS during the link stage for the case > when Qemu is configured with --enable-xen and --disable-xen-pci-passthrough, > in which case it does nothing. > > The new xen_igd_clear_slot function overrides qdev->realize of the parent > PCI device class to enable the Intel IGD to occupy slot 2 on the PCI bus > since slot 2 was reserved by xen_igd_reserve_slot when the PCI bus was > created in hw/i386/pc_piix.c for the case when igd-passthru=on. > > Move the call to xen_host_pci_device_get, and the associated error > handling, from xen_pt_realize to the new xen_igd_clear_slot function to > initialize the device class and vendor values which enables the checks for > the Intel IGD to succeed. The verification that the host device is an > Intel IGD to be passed through is done by checking the domain, bus, slot, > and function values as well as by checking that gfx_passthru is enabled, > the device class is VGA, and the device vendor in Intel. > > Signed-off-by: Chuck Zmudzinski > --- > Notes that might be helpful to reviewers of patched code in hw/xen: > > The new functions and types are based on recommendations from Qemu docs: > https://qemu.readthedocs.io/en/latest/devel/qom.html > > Notes that might be helpful to reviewers of patched code in hw/i386: > > The small patch to hw/i386/pc_piix.c is protected by CONFIG_XEN so it does > not affect builds that do not have CONFIG_XEN defined. > > xen_igd_gfx_pt_enabled() in the patched hw/i386/pc_piix.c file is an > existing function that is only true when Qemu is built with > xen-pci-passthrough enabled and the administrator has configured the Xen > HVM guest with Qemu's igd-passthru=on option. > > v2: Remove From: tag at top of commit message > > v3: Changed the test for the Intel IGD in xen_igd_clear_slot: > > if (is_igd_vga_passthrough(&s->real_device) && > (s->real_device.vendor_id == PCI_VENDOR_ID_INTEL)) { > > is changed to > > if (xen_igd_gfx_pt_enabled() && (s->hostaddr.slot == 2) > && (s->hostaddr.function == 0)) { > > I hoped that I could use the test in v2, since it matches the > other tests for the Intel IGD in Qemu and Xen, but those tests > do not work because the necessary data structures are not set with > their values yet. So instead use the test that the administrator > has enabled gfx_passthru and the device address on the host is > 02.0. This test does detect the Intel IGD correctly. > > v4: Use brchuckz@aol.com instead of brchuckz@netscape.net for the author's > email address to match the address used by the same author in commits > be9c61da and c0e86b76 > > Change variable for XEN_PT_DEVICE_CLASS: xptc changed to xpdc > > v5: The patch of xen_pt.c was re-worked to allow a more consistent test > for the Intel IGD that uses the same criteria as in other places. > This involved moving the call to xen_host_pci_device_get from > xen_pt_realize to xen_igd_clear_slot and updating the checks for the > Intel IGD in xen_igd_clear_slot: > > if (xen_igd_gfx_pt_enabled() && (s->hostaddr.slot == 2) > && (s->hostaddr.function == 0)) { > > is changed to > > if (is_igd_vga_passthrough(&s->real_device) && > s->real_device.domain == 0 && s->real_device.bus == 0 && > s->real_device.dev == 2 && s->real_device.func == 0 && > s->real_device.vendor_id == PCI_VENDOR_ID_INTEL) { > > Added an explanation for the move of xen_host_pci_device_get from > xen_pt_realize to xen_igd_clear_slot to the commit message. > > Rebase. > > v6: Fix logging by removing these lines from the move from xen_pt_realize > to xen_igd_clear_slot that was done in v5: > > XEN_PT_LOG(d, "Assigning real physical device %02x:%02x.%d" > " to devfn 0x%x\n", > s->hostaddr.bus, s->hostaddr.slot, s->hostaddr.function, > s->dev.devfn); > > This log needs to be in xen_pt_realize because s->dev.devfn is not > set yet in xen_igd_clear_slot. > > v7: The v7 that was posted to the mailing list was incorrect. v8 is what > v7 was intended to be. > > v8: Inhibit out of context log message and needless processing by > adding 2 lines at the top of the new xen_igd_clear_slot function: > > if (!(pci_bus->slot_reserved_mask & XEN_PCI_IGD_SLOT_MASK)) > return; > > Rebase. This removed an unnecessary header file from xen_pt.h > > hw/i386/pc_piix.c | 3 +++ > hw/xen/xen_pt.c | 49 ++++++++++++++++++++++++++++++++++++-------- > hw/xen/xen_pt.h | 16 +++++++++++++++ > hw/xen/xen_pt_stub.c | 4 ++++ > 4 files changed, 63 insertions(+), 9 deletions(-) > > diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c > index b48047f50c..bc5efa4f59 100644 > --- a/hw/i386/pc_piix.c > +++ b/hw/i386/pc_piix.c > @@ -405,6 +405,9 @@ static void pc_xen_hvm_init(MachineState *machine) > } > > pc_xen_hvm_init_pci(machine); > + if (xen_igd_gfx_pt_enabled()) { > + xen_igd_reserve_slot(pcms->bus); > + } > pci_create_simple(pcms->bus, -1, "xen-platform"); > } > #endif I would even maybe go further and move the whole logic into xen_igd_reserve_slot. And I would even just name it xen_hvm_init_reserved_slots without worrying about the what or why at the pc level. At this point it will be up to Xen maintainers. > diff --git a/hw/xen/xen_pt.c b/hw/xen/xen_pt.c > index 0ec7e52183..eff38155ef 100644 > --- a/hw/xen/xen_pt.c > +++ b/hw/xen/xen_pt.c > @@ -780,15 +780,6 @@ static void xen_pt_realize(PCIDevice *d, Error **errp) > s->hostaddr.bus, s->hostaddr.slot, s->hostaddr.function, > s->dev.devfn); > > - xen_host_pci_device_get(&s->real_device, > - s->hostaddr.domain, s->hostaddr.bus, > - s->hostaddr.slot, s->hostaddr.function, > - errp); > - if (*errp) { > - error_append_hint(errp, "Failed to \"open\" the real pci device"); > - return; > - } > - > s->is_virtfn = s->real_device.is_virtfn; > if (s->is_virtfn) { > XEN_PT_LOG(d, "%04x:%02x:%02x.%d is a SR-IOV Virtual Function\n", > @@ -950,11 +941,50 @@ static void xen_pci_passthrough_instance_init(Object *obj) > PCI_DEVICE(obj)->cap_present |= QEMU_PCI_CAP_EXPRESS; > } > > +void xen_igd_reserve_slot(PCIBus *pci_bus) > +{ > + XEN_PT_LOG(0, "Reserving PCI slot 2 for IGD\n"); > + pci_bus->slot_reserved_mask |= XEN_PCI_IGD_SLOT_MASK; > +} > + > +static void xen_igd_clear_slot(DeviceState *qdev, Error **errp) > +{ > + ERRP_GUARD(); > + PCIDevice *pci_dev = (PCIDevice *)qdev; > + XenPCIPassthroughState *s = XEN_PT_DEVICE(pci_dev); > + XenPTDeviceClass *xpdc = XEN_PT_DEVICE_GET_CLASS(s); > + PCIBus *pci_bus = pci_get_bus(pci_dev); > + > + if (!(pci_bus->slot_reserved_mask & XEN_PCI_IGD_SLOT_MASK)) > + return; > + > + xen_host_pci_device_get(&s->real_device, > + s->hostaddr.domain, s->hostaddr.bus, > + s->hostaddr.slot, s->hostaddr.function, > + errp); > + if (*errp) { > + error_append_hint(errp, "Failed to \"open\" the real pci device"); > + return; > + } > + > + if (is_igd_vga_passthrough(&s->real_device) && > + s->real_device.domain == 0 && s->real_device.bus == 0 && > + s->real_device.dev == 2 && s->real_device.func == 0 && > + s->real_device.vendor_id == PCI_VENDOR_ID_INTEL) { how about macros for these? #define XEN_PCI_IGD_DOMAIN 0 #define XEN_PCI_IGD_BUS 0 #define XEN_PCI_IGD_DEV 2 #define XEN_PCI_IGD_FN 0 > + pci_bus->slot_reserved_mask &= ~XEN_PCI_IGD_SLOT_MASK; If you are going to do this, you should set it back either after pci_qdev_realize or in unrealize, for symmetry. > + XEN_PT_LOG(pci_dev, "Intel IGD found, using slot 2\n"); > + } > + xpdc->pci_qdev_realize(qdev, errp); > +} > + > static void xen_pci_passthrough_class_init(ObjectClass *klass, void *data) > { > DeviceClass *dc = DEVICE_CLASS(klass); > PCIDeviceClass *k = PCI_DEVICE_CLASS(klass); > > + XenPTDeviceClass *xpdc = XEN_PT_DEVICE_CLASS(klass); > + xpdc->pci_qdev_realize = dc->realize; > + dc->realize = xen_igd_clear_slot; > k->realize = xen_pt_realize; > k->exit = xen_pt_unregister_device; > k->config_read = xen_pt_pci_read_config; > @@ -977,6 +1007,7 @@ static const TypeInfo xen_pci_passthrough_info = { > .instance_size = sizeof(XenPCIPassthroughState), > .instance_finalize = xen_pci_passthrough_finalize, > .class_init = xen_pci_passthrough_class_init, > + .class_size = sizeof(XenPTDeviceClass), > .instance_init = xen_pci_passthrough_instance_init, > .interfaces = (InterfaceInfo[]) { > { INTERFACE_CONVENTIONAL_PCI_DEVICE }, > diff --git a/hw/xen/xen_pt.h b/hw/xen/xen_pt.h > index cf10fc7bbf..8c25932b4b 100644 > --- a/hw/xen/xen_pt.h > +++ b/hw/xen/xen_pt.h > @@ -2,6 +2,7 @@ > #define XEN_PT_H > > #include "hw/xen/xen_common.h" > +#include "hw/pci/pci_bus.h" > #include "xen-host-pci-device.h" > #include "qom/object.h" > > @@ -40,7 +41,20 @@ typedef struct XenPTReg XenPTReg; > #define TYPE_XEN_PT_DEVICE "xen-pci-passthrough" > OBJECT_DECLARE_SIMPLE_TYPE(XenPCIPassthroughState, XEN_PT_DEVICE) > > +#define XEN_PT_DEVICE_CLASS(klass) \ > + OBJECT_CLASS_CHECK(XenPTDeviceClass, klass, TYPE_XEN_PT_DEVICE) > +#define XEN_PT_DEVICE_GET_CLASS(obj) \ > + OBJECT_GET_CLASS(XenPTDeviceClass, obj, TYPE_XEN_PT_DEVICE) > + > +typedef void (*XenPTQdevRealize)(DeviceState *qdev, Error **errp); > + > +typedef struct XenPTDeviceClass { > + PCIDeviceClass parent_class; > + XenPTQdevRealize pci_qdev_realize; > +} XenPTDeviceClass; > + > uint32_t igd_read_opregion(XenPCIPassthroughState *s); > +void xen_igd_reserve_slot(PCIBus *pci_bus); > void igd_write_opregion(XenPCIPassthroughState *s, uint32_t val); > void xen_igd_passthrough_isa_bridge_create(XenPCIPassthroughState *s, > XenHostPCIDevice *dev); > @@ -75,6 +89,8 @@ typedef int (*xen_pt_conf_byte_read) > > #define XEN_PCI_INTEL_OPREGION 0xfc > > +#define XEN_PCI_IGD_SLOT_MASK 0x4UL /* Intel IGD slot_reserved_mask */ > + I think you want to calculate this based on dev fn: #define XEN_PCI_IGD_SLOT_MASK \ (0x1 << PCI_SLOT(PCI_DEVFN(XEN_PCI_IGD_DEV, XEN_PCI_IGD_FN))) > typedef enum { > XEN_PT_GRP_TYPE_HARDWIRED = 0, /* 0 Hardwired reg group */ > XEN_PT_GRP_TYPE_EMU, /* emul reg group */ > diff --git a/hw/xen/xen_pt_stub.c b/hw/xen/xen_pt_stub.c > index 2d8cac8d54..5c108446a8 100644 > --- a/hw/xen/xen_pt_stub.c > +++ b/hw/xen/xen_pt_stub.c > @@ -20,3 +20,7 @@ void xen_igd_gfx_pt_set(bool value, Error **errp) > error_setg(errp, "Xen PCI passthrough support not built in"); > } > } > + > +void xen_igd_reserve_slot(PCIBus *pci_bus) > +{ > +} > -- > 2.39.0