Re: [PATCH] pci-assign: Do not expose MSI/MSI-X if the kernel does not support it

[Alex Williamson <alex.williamson@redhat.com>]

On Tue, 2011-08-02 at 14:27 +0200, Jan Kiszka wrote:
> Add checks for KVM_CAP_ASSIGN_DEV_IRQ (MSI) and KVM_CAP_DEVICE_MSIX, do
> not set up MSI/MSI-X if the required kernel features are missing.
> 
> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
> ---
>  hw/device-assignment.c |    6 ++++--
>  1 files changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/device-assignment.c b/hw/device-assignment.c
> index 4cc7b1a..7e965cb 100644
> --- a/hw/device-assignment.c
> +++ b/hw/device-assignment.c
> @@ -1201,7 +1201,8 @@ static int assigned_device_pci_cap_init(PCIDevice *pci_dev)
>  
>      /* Expose MSI capability
>       * MSI capability is the 1st capability in capability config */
> -    if ((pos = pci_find_cap_offset(pci_dev, PCI_CAP_ID_MSI, 0))) {
> +    pos = pci_find_cap_offset(pci_dev, PCI_CAP_ID_MSI, 0);
> +    if (pos != 0 && kvm_check_extension(kvm_state, KVM_CAP_ASSIGN_DEV_IRQ)) {

Is it even useful to have a device assigned w/o KVM_CAP_ASSIGN_DEV_IRQ?
Thanks,

Alex

>          dev->cap.available |= ASSIGNED_DEVICE_CAP_MSI;
>          /* Only 32-bit/no-mask currently supported */
>          if ((ret = pci_add_capability(pci_dev, PCI_CAP_ID_MSI, pos, 10)) < 0) {
> @@ -1222,7 +1223,8 @@ static int assigned_device_pci_cap_init(PCIDevice *pci_dev)
>          pci_set_word(pci_dev->wmask + pos + PCI_MSI_DATA_32, 0xffff);
>      }
>      /* Expose MSI-X capability */
> -    if ((pos = pci_find_cap_offset(pci_dev, PCI_CAP_ID_MSIX, 0))) {
> +    pos = pci_find_cap_offset(pci_dev, PCI_CAP_ID_MSIX, 0);
> +    if (pos != 0 && kvm_check_extension(kvm_state, KVM_CAP_DEVICE_MSIX)) {
>          int bar_nr;
>          uint32_t msix_table_entry;
>