Re: [PATCH 5/6] device assignment: support for assigning PCI devices to guests

[Muli Ben-Yehuda <muli@il.ibm.com>]

On Tue, Oct 28, 2008 at 05:53:05PM +0200, Muli Ben-Yehuda wrote:
> On Tue, Oct 28, 2008 at 10:45:57AM -0500, Anthony Liguori wrote:
> 
> >> +ifeq ($(USE_KVM), 1)
> >> +OBJS+= device-assignment.o
> >> +endif
> >
> > I don't think you want to build this on PPC so I think you need a
> > stronger check.
> 
> Good point. How about checking TARGET_BASE_ARCH = i386?

Turns out this stanza is already enclosed in exactly that.

> >> +#ifdef KVM_CAP_IOMMU
> >> +        /* We always enable the IOMMU if present
> >> +         * (or when not disabled on the command line)
> >> +         */
> >> +        r = kvm_check_extension(kvm_context, KVM_CAP_IOMMU);
> >> +        if (r && !disable_iommu)
> >> +            assigned_dev_data.flags |= KVM_DEV_ASSIGN_ENABLE_IOMMU;
> >> +#endif
> >> +        r = kvm_assign_pci_device(kvm_context, &assigned_dev_data);
> >> +        if (r < 0) {
> >> +            fprintf(stderr, "Could not notify kernel about "
> >> +                "assigned device \"%s\"\n", e_dev_name);
> >> +            perror("register_real_device");
> >> +            goto out;
> >> +        }
> >> +    }
> >>   
> >
> > You still succeed if KVM_CAP_DEVICE_ASSIGNMENT isn't defined?
> > That means a newer userspace compiled on an older kernel will
> > silently fail if they try to do device assignment.  There's
> > probably no reason to build this file if KVM_CAP_DEVICE_ASSIGNMENT
> > isn't defined (see how the in-kernel PIT gets conditionally build
> > depending on whether that cap is available).
> 
> Ok, I'll take a look at this.

I reworked it per your suggestion so that device assignment is a kvm
only feature for now. I am pretty sure Amit intended for the patches
to support device assignment without kvm too, but getting rid of it
did make things simpler.

cheers,
Muli
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