On Thu, Jun 04, 2015 at 04:20:45PM +0100, Andre Przywara wrote:
> In PCI config space there is an interrupt line field (offset 0x3f),
> which is used to initially communicate the IRQ line number from
> firmware to the OS. _Hardware_ should never use this information,
> as the OS is free to write any information in there.
> But kvmtool uses this number when it triggers IRQs in the guest,
> which fails starting with Linux 3.19-rc1, where the PCI layer starts
> writing the virtual IRQ number in there.
>
> Fix that by storing the IRQ number in a separate field in
> struct virtio_pci, which is independent from the PCI config space
> and cannot be influenced by the guest.
> This fixes ARM/ARM64 guests using PCI with newer kernels.
>
> Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx>
> ---
> include/kvm/virtio-pci.h | 8 ++++++++
> virtio/pci.c | 9 ++++++---
> 2 files changed, 14 insertions(+), 3 deletions(-)
>
> diff --git a/include/kvm/virtio-pci.h b/include/kvm/virtio-pci.h
> index c795ce7..b70cadd 100644
> --- a/include/kvm/virtio-pci.h
> +++ b/include/kvm/virtio-pci.h
> @@ -30,6 +30,14 @@ struct virtio_pci {
> u8 isr;
> u32 features;
>
> + /*
> + * We cannot rely on the INTERRUPT_LINE byte in the config space once
> + * we have run guest code, as the OS is allowed to use that field
> + * as a scratch pad to communicate between driver and PCI layer.
> + * So store our legacy interrupt line number in here for internal use.
> + */
> + u8 legacy_irq_line;
> +
> /* MSI-X */
> u16 config_vector;
> u32 config_gsi;
> diff --git a/virtio/pci.c b/virtio/pci.c
> index 7556239..e17e5a9 100644
> --- a/virtio/pci.c
> +++ b/virtio/pci.c
> @@ -141,7 +141,7 @@ static bool virtio_pci__io_in(struct ioport *ioport, struct kvm_cpu *vcpu, u16 p
> break;
> case VIRTIO_PCI_ISR:
> ioport__write8(data, vpci->isr);
> - kvm__irq_line(kvm, vpci->pci_hdr.irq_line, VIRTIO_IRQ_LOW);
> + kvm__irq_line(kvm, vpci->legacy_irq_line, VIRTIO_IRQ_LOW);
> vpci->isr = VIRTIO_IRQ_LOW;
> break;
> default:
> @@ -299,7 +299,7 @@ int virtio_pci__signal_vq(struct kvm *kvm, struct virtio_device *vdev, u32 vq)
> kvm__irq_trigger(kvm, vpci->gsis[vq]);
> } else {
> vpci->isr = VIRTIO_IRQ_HIGH;
> - kvm__irq_trigger(kvm, vpci->pci_hdr.irq_line);
> + kvm__irq_trigger(kvm, vpci->legacy_irq_line);
> }
> return 0;
> }
> @@ -323,7 +323,7 @@ int virtio_pci__signal_config(struct kvm *kvm, struct virtio_device *vdev)
> kvm__irq_trigger(kvm, vpci->config_gsi);
> } else {
> vpci->isr = VIRTIO_PCI_ISR_CONFIG;
> - kvm__irq_trigger(kvm, vpci->pci_hdr.irq_line);
> + kvm__irq_trigger(kvm, vpci->legacy_irq_line);
> }
>
> return 0;
> @@ -422,6 +422,9 @@ int virtio_pci__init(struct kvm *kvm, void *dev, struct virtio_device *vdev,
> if (r < 0)
> goto free_msix_mmio;
>
> + /* save the IRQ that device__register() has allocated */
> + vpci->legacy_irq_line = vpci->pci_hdr.irq_line;
I'd rather we used the container_of trick that we do for virtio-mmio
devices when assigning the irq in device__register. Then we can avoid
this line completely.
Will
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