Re: [Qemu-devel] [PATCH v10 27/26] intel_iommu: disallow kernel-irqchip=on with IR

[Peter Xu]

On Mon, Jul 11, 2016 at 01:17:40PM +0300, David Kiarie wrote:
> On Fri, Jun 24, 2016 at 10:10 AM, Peter Xu <address@hidden> wrote:
> > When user specify "kernel-irqchip=on", throw error and then quit.
> >
> > Signed-off-by: Peter Xu <address@hidden>
> > ---
> >
> > One more patch for this series. Without this one, guest kernel will
> > possibly hang. This is not user friendly.
> >
> >  hw/i386/intel_iommu.c | 9 +++++++++
> >  1 file changed, 9 insertions(+)
> >
> > diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
> > index 4ff9a24..618b0f9 100644
> > --- a/hw/i386/intel_iommu.c
> > +++ b/hw/i386/intel_iommu.c
> > @@ -20,6 +20,7 @@
> >   */
> >
> >  #include "qemu/osdep.h"
> > +#include "qemu/error-report.h"
> >  #include "hw/sysbus.h"
> >  #include "exec/address-spaces.h"
> >  #include "intel_iommu_internal.h"
> > @@ -29,6 +30,7 @@
> >  #include "hw/boards.h"
> >  #include "hw/i386/x86-iommu.h"
> >  #include "hw/pci-host/q35.h"
> > +#include "sysemu/kvm.h"
> >
> >  /*#define DEBUG_INTEL_IOMMU*/
> >  #ifdef DEBUG_INTEL_IOMMU
> > @@ -2458,6 +2460,13 @@ static void vtd_realize(DeviceState *dev, Error 
> > **errp)
> >      bus->iommu_opaque = dev;
> >      /* Pseudo address space under root PCI bus. */
> >      pcms->ioapic_as = vtd_host_dma_iommu(bus, s, Q35_PSEUDO_DEVFN_IOAPIC);
> > +
> > +    /* Currently Intel IOMMU IR only support "kernel-irqchip={off|split}" 
> > */
> > +    if (kvm_irqchip_in_kernel() && !kvm_irqchip_is_split()) {
> > +        error_report("Intel Interrupt Remapping cannot work with "
> > +                     "kernel-irqchip=on, please use 'split|off'.");
> > +        exit(1);
> > +    }
> >  }
> 
> Shouldn't you be checking whether VT-d interrupt remapping is
> enabled(I'm assuming it's off by default) before you ensure
> kernel-irqchip=off|split ? Doesn't the above imply that one can't use
> VT-d with kernel_irqchip=on (regardless of whether IR is enabled) ?

Yes we should allow ir=off and kernel-irqchip=on. Will fix in v12,
thanks!

-- peterx