Re: [Qemu-devel] [PATCH RFC 1/4] intel_iommu: Sanity check vfio-pci config on machine init done

[Auger Eric <eric.auger@redhat.com>]

Hi Peter,
On 8/12/19 9:45 AM, Peter Xu wrote:
> This check was previously only happened when the IOMMU is enabled in
s/happened/happening
> the guest.  It was always too late because the enabling of IOMMU
> normally only happens during the boot of guest OS.  It means that we
> can bail out and exit directly during the guest OS boots if the
> configuration of devices are not supported.  Or, if the guest didn't
> enable vIOMMU at all, then the user can use the guest normally but as
> long as it reconfigure the guest OS to enable the vIOMMU then reboot,
reconfigures, and then reboots
> the user will see the panic right after the reset when the next boot
> starts.
> 
> Let's make this failure even earlier so that we force the user to use
> caching-mode for vfio-pci devices when with the vIOMMU.  So the user
> won't get surprise at least during execution of the guest, which seems
> a bit nicer.
> 
> This will affect some user who didn't enable vIOMMU in the guest OS
> but was using vfio-pci and the vtd device in the past.  However I hope
> it's not a majority because not enabling vIOMMU with the device
> attached is actually meaningless.
> 
> We still keep the old assertion for safety so far because the hotplug
> path could still reach it, so far.
> 
> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---
>  hw/i386/intel_iommu.c | 38 +++++++++++++++++++++++++++++++++++---
>  1 file changed, 35 insertions(+), 3 deletions(-)
> 
> diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
> index de86f53b4e..642dd595ed 100644
> --- a/hw/i386/intel_iommu.c
> +++ b/hw/i386/intel_iommu.c
> @@ -61,6 +61,13 @@
>  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)
>  {
> @@ -2926,9 +2933,7 @@ static void vtd_iommu_notify_flag_changed(IOMMUMemoryRegion *iommu,
>      IntelIOMMUState *s = vtd_as->iommu_state;
>  
>      if (!s->caching_mode && new & IOMMU_NOTIFIER_MAP) {
> -        error_report("We need to set caching-mode=on for intel-iommu to enable "
> -                     "device assignment with IOMMU protection.");
> -        exit(1);
> +        vtd_panic_require_caching_mode();
>      }
>  
>      /* Update per-address-space notifier flags */
> @@ -3696,6 +3701,32 @@ 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());
> @@ -3741,6 +3772,7 @@ static void vtd_realize(DeviceState *dev, Error **errp)
>      pci_setup_iommu(bus, vtd_host_dma_iommu, dev);
>      /* Pseudo address space under root PCI bus. */
>      pcms->ioapic_as = vtd_host_dma_iommu(bus, s, Q35_PSEUDO_DEVFN_IOAPIC);
> +    qemu_add_machine_init_done_notifier(&vtd_machine_done_notify);
This does not compile anymore on master. I think sysemu/sysemu.h needs
to be included as declaration of qemu_add_machine_init_done_notifier is
not found.

Besides
Reviewed-by: Eric Auger <eric.auger@redhat.com>

Thanks

Eric
>  }
>  
>  static void vtd_class_init(ObjectClass *klass, void *data)
>