On 9/19/25 09:06, Zhenzhong Duan wrote:
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]> --- hw/i386/intel_iommu.c | 47 ++++++------------------------------------- hw/i386/pc.c | 20 ------------------ 2 files changed, 6 insertions(+), 61 deletions(-)
This is a nice cleanup. Acked-by: Cédric Le Goater <[email protected]> Thanks, C.
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;
