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Re: [Qemu-devel] [PATCH for-1.3] vfio-pci: Fix KVM disabled path


From: Peter Maydell
Subject: Re: [Qemu-devel] [PATCH for-1.3] vfio-pci: Fix KVM disabled path
Date: Fri, 30 Nov 2012 18:57:15 +0000

On 27 November 2012 19:45, Alex Williamson <address@hidden> wrote:
> kvm_check_extension() explodes when KVM isn't enabled so we need to
> first test whether KVM is enabled.  Use kvm_irqchip_in_kernel() for
> this since it matches the test we do before using this result.

> --- a/hw/vfio_pci.c
> +++ b/hw/vfio_pci.c
> @@ -438,7 +438,8 @@ static int vfio_enable_intx(VFIODevice *vdev)
>       * Only conditional to avoid generating error messages on platforms
>       * where we won't actually use the result anyway.
>       */
> -    if (kvm_check_extension(kvm_state, KVM_CAP_IRQFD_RESAMPLE)) {
> +    if (kvm_irqchip_in_kernel() &&
> +        kvm_check_extension(kvm_state, KVM_CAP_IRQFD_RESAMPLE)) {
>          vdev->intx.route = pci_device_route_intx_to_irq(&vdev->pdev,
>                                                          vdev->intx.pin);


vfio_pci is supposed to be architecture-independent code, right?
kvm.h says you mustn't use kvm_irqchip_in_kernel() in such code
(its semantics vary from arch to arch). I think kvm_enabled()
is sufficient here since what we're actually guarding is just
the kvm_check_extension call.

-- PMM



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