Re: [Qemu-devel] [PATCH v3 2/2] i440fx: print an error message if user tries to enable iommu

[Markus Armbruster]

Bandan Das <address@hidden> writes:

> There's no indication of any sort that i440fx doesn't support
> "iommu=on"
>
> Reviewed-by: Eric Blake <address@hidden>
> Signed-off-by: Bandan Das <address@hidden>
> ---
>  hw/pci-host/piix.c | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/hw/pci-host/piix.c b/hw/pci-host/piix.c
> index 7b2fbf9..715208b 100644
> --- a/hw/pci-host/piix.c
> +++ b/hw/pci-host/piix.c
> @@ -34,6 +34,7 @@
>  #include "sysemu/sysemu.h"
>  #include "hw/i386/ioapic.h"
>  #include "qapi/visitor.h"
> +#include "qemu/error-report.h"
>  
>  /*
>   * I440FX chipset data sheet.
> @@ -301,6 +302,10 @@ static void i440fx_pcihost_realize(DeviceState *dev, 
> Error **errp)
>  static void i440fx_realize(PCIDevice *dev, Error **errp)
>  {
>      dev->config[I440FX_SMRAM] = 0x02;
> +
> +    if (object_property_get_bool(qdev_get_machine(), "iommu", NULL)) {
> +        error_report("warning: i440fx doesn't support emulated iommu");
> +    }
>  }
>  
>  PCIBus *i440fx_init(const char *host_type, const char *pci_type,

Hmm.

If I understand things correctly, we add property "iommu" to *any*
machine, whether it supports it or not (see machine_initfn() in
hw/core/machine.c).

Most machines don't support it.  You add a warning to one of them.
Why to that one and not the others?

Shouldn't we add properties only to machines where they make sense?
Adding them indiscrimiately defeats QOM introspection.