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

[Jan Kiszka <jan.kiszka@siemens.com>]

On 2011-08-02 19:02, Alex Williamson wrote:
> 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?

If that feature is lacking, we fall back to the old KVM_ASSIGN_IRQ
interface. I guess that used to work, but I bet no one tested it
recently. However, the code is there, also in the kvm core.

Jan

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