Hi Zhenzhnog, Nice!
Reviewed-by: Clément Mathieu--Drif <[email protected]> Thanks On Fri, 2025-09-19 at 03:06 -0400, Zhenzhong Duan wrote: > Caution: External email. Do not open attachments or click links, unless this > email comes from a known sender and you know the content is safe. > > > In early days, we have different tricks to ensure caching-mode=on with VFIO > device: > > 28cf553afe ("intel_iommu: Sanity check vfio-pci config on machine init done") > > c6cbc29d36 ("pc/q35: Disallow vfio-pci hotplug without VT-d caching mode") > b8d78277c0 ("intel-iommu: fail MAP notifier without caching mode") > > Because without caching mode, MAP notifier won't work correctly since guest > won't send IOTLB update event when it establishes new mappings in the I/O > page > tables. > > Now with host IOMMU device interface between VFIO and vIOMMU, we can simplify > > it with a small check in set_iommu_device(). This also works for future VDPA > implementation which may also need caching mode on. > > For coldplug VFIO device: > > qemu-system-x86_64: -device > vfio-pci,host=0000:3b:00.0,id=hostdev3,bus=root0,iommufd=iommufd0: vfio > 0000:3b:00.0: Failed to set vIOMMU: Device assignment is not allowed without > enabling caching-mode=on for Intel IOMMU. > > For hotplug VFIO device: > > Error: vfio 0000:3b:00.0: Failed to set vIOMMU: Device assignment is not > allowed without enabling caching-mode=on for Intel IOMMU. > > Signed-off-by: Zhenzhong Duan > <[[email protected]](mailto:[email protected])> > --- > hw/i386/intel_iommu.c | 47 ++++++------------------------------------- > hw/i386/pc.c | 20 ------------------ > 2 files changed, 6 insertions(+), 61 deletions(-) > > diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c > index f04300022e..5c67b42dde 100644 > --- a/hw/i386/intel_iommu.c > +++ b/hw/i386/intel_iommu.c > @@ -85,13 +85,6 @@ struct vtd_iotlb_key { > static void vtd_address_space_refresh_all(IntelIOMMUState *s); > static void vtd_address_space_unmap(VTDAddressSpace *as, IOMMUNotifier *n); > > -static void vtd_panic_require_caching_mode(void) > -{ > - error_report("We need to set caching-mode=on for intel-iommu to enable " > > - "device assignment with IOMMU protection."); > - exit(1); > -} > - > static void vtd_define_quad(IntelIOMMUState *s, hwaddr addr, uint64_t val, > uint64_t wmask, uint64_t w1cmask) > { > @@ -3731,13 +3724,6 @@ static int > vtd_iommu_notify_flag_changed(IOMMUMemoryRegion *iommu, > "Snoop Control with vhost or VFIO is not > supported"); > return -ENOTSUP; > } > - if (!s->caching_mode && (new & IOMMU_NOTIFIER_MAP)) { > - error_setg_errno(errp, ENOTSUP, > - "device %02x.%02x.%x requires caching mode", > - pci_bus_num(vtd_as->bus), PCI_SLOT(vtd_as->devfn), > - PCI_FUNC(vtd_as->devfn)); > - return -ENOTSUP; > - } > if (!x86_iommu->dt_supported && (new & IOMMU_NOTIFIER_DEVIOTLB_UNMAP)) { > > error_setg_errno(errp, ENOTSUP, > "device %02x.%02x.%x requires device IOTLB mode", > @@ -4378,6 +4364,12 @@ static bool vtd_dev_set_iommu_device(PCIBus *bus, void > *opaque, int devfn, > > assert(hiod); > > + if (!s->caching_mode) { > + error_setg(errp, "Device assignment is not allowed without enabling > " > + "caching-mode=on for Intel IOMMU."); > + return false; > + } > + > vtd_iommu_lock(s); > > if (g_hash_table_lookup(s->vtd_host_iommu_dev, &key)) { > @@ -4910,32 +4902,6 @@ static bool vtd_decide_config(IntelIOMMUState *s, > Error **errp) > return true; > } > > -static int vtd_machine_done_notify_one(Object *child, void *unused) > -{ > - IntelIOMMUState *iommu = INTEL_IOMMU_DEVICE(x86_iommu_get_default()); > - > - /* > - * We hard-coded here because vfio-pci is the only special case > - * here. Let's be more elegant in the future when we can, but so > - * far there seems to be no better way. > - */ > - if (object_dynamic_cast(child, "vfio-pci") && !iommu->caching_mode) { > - vtd_panic_require_caching_mode(); > - } > - > - return 0; > -} > - > -static void vtd_machine_done_hook(Notifier *notifier, void *unused) > -{ > - object_child_foreach_recursive(object_get_root(), > - vtd_machine_done_notify_one, NULL); > -} > - > -static Notifier vtd_machine_done_notify = { > - .notify = vtd_machine_done_hook, > -}; > - > static void vtd_realize(DeviceState *dev, Error **errp) > { > MachineState *ms = MACHINE(qdev_get_machine()); > @@ -4990,7 +4956,6 @@ static void vtd_realize(DeviceState *dev, Error **errp) > > pci_setup_iommu(bus, &vtd_iommu_ops, dev); > /* Pseudo address space under root PCI bus. */ > x86ms->ioapic_as = vtd_host_dma_iommu(bus, s, Q35_PSEUDO_DEVFN_IOAPIC); > - qemu_add_machine_init_done_notifier(&vtd_machine_done_notify); > } > > static void vtd_class_init(ObjectClass *klass, const void *data) > diff --git a/hw/i386/pc.c b/hw/i386/pc.c > index bc048a6d13..01cd9a67db 100644 > --- a/hw/i386/pc.c > +++ b/hw/i386/pc.c > @@ -1720,25 +1720,6 @@ static void pc_machine_wakeup(MachineState *machine) > cpu_synchronize_all_post_reset(); > } > > -static bool pc_hotplug_allowed(MachineState *ms, DeviceState *dev, Error > **errp) > -{ > - X86IOMMUState *iommu = x86_iommu_get_default(); > - IntelIOMMUState *intel_iommu; > - > - if (iommu && > - object_dynamic_cast((Object *)iommu, TYPE_INTEL_IOMMU_DEVICE) && > - object_dynamic_cast((Object *)dev, "vfio-pci")) { > - intel_iommu = INTEL_IOMMU_DEVICE(iommu); > - if (!intel_iommu->caching_mode) { > - error_setg(errp, "Device assignment is not allowed without " > - "enabling caching-mode=on for Intel IOMMU."); > - return false; > - } > - } > - > - return true; > -} > - > static void pc_machine_class_init(ObjectClass *oc, const void *data) > { > MachineClass *mc = MACHINE_CLASS(oc); > @@ -1758,7 +1739,6 @@ static void pc_machine_class_init(ObjectClass *oc, > const void *data) > x86mc->apic_xrupt_override = true; > assert(!mc->get_hotplug_handler); > mc->get_hotplug_handler = pc_get_hotplug_handler; > - mc->hotplug_allowed = pc_hotplug_allowed; > mc->auto_enable_numa_with_memhp = true; > mc->auto_enable_numa_with_memdev = true; > mc->has_hotpluggable_cpus = true; > -- > 2.47.1 >
