Re: [Qemu-devel] [PATCH] pci-assign: limit # of msix vectors

[Alex Williamson]

On Mon, 2014-04-28 at 17:02 +0300, Michael S. Tsirkin wrote:
> KVM only supports MSIX table size up to 256 vectors,
> but some assigned devices support more vectors,
> at the moment attempts to assign them fail with EINVAL.
> 
> Tweak the MSIX capability exposed to guest to limit table size
> to a supported value.
> 
> Signed-off-by: Michael S. Tsirkin <address@hidden>
> Tested-by: Gonglei <address@hidden>
> ---
>  hw/i386/kvm/pci-assign.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)

Acked-by: Alex Williamson <address@hidden>


> diff --git a/hw/i386/kvm/pci-assign.c b/hw/i386/kvm/pci-assign.c
> index a825871..76aa86e 100644
> --- a/hw/i386/kvm/pci-assign.c
> +++ b/hw/i386/kvm/pci-assign.c
> @@ -1258,6 +1258,7 @@ static int assigned_device_pci_cap_init(PCIDevice 
> *pci_dev)
>      if (pos != 0 && kvm_device_msix_supported(kvm_state)) {
>          int bar_nr;
>          uint32_t msix_table_entry;
> +        uint16_t msix_max;
>  
>          if (!check_irqchip_in_kernel()) {
>              return -ENOTSUP;
> @@ -1269,9 +1270,10 @@ static int assigned_device_pci_cap_init(PCIDevice 
> *pci_dev)
>          }
>          pci_dev->msix_cap = pos;
>  
> -        pci_set_word(pci_dev->config + pos + PCI_MSIX_FLAGS,
> -                     pci_get_word(pci_dev->config + pos + PCI_MSIX_FLAGS) &
> -                     PCI_MSIX_FLAGS_QSIZE);
> +        msix_max = (pci_get_word(pci_dev->config + pos + PCI_MSIX_FLAGS) &
> +                    PCI_MSIX_FLAGS_QSIZE) + 1;
> +        msix_max = MIN(msix_max, KVM_MAX_MSIX_PER_DEV);
> +        pci_set_word(pci_dev->config + pos + PCI_MSIX_FLAGS, msix_max - 1);
>  
>          /* Only enable and function mask bits are writable */
>          pci_set_word(pci_dev->wmask + pos + PCI_MSIX_FLAGS,
> @@ -1281,9 +1283,7 @@ static int assigned_device_pci_cap_init(PCIDevice 
> *pci_dev)
>          bar_nr = msix_table_entry & PCI_MSIX_FLAGS_BIRMASK;
>          msix_table_entry &= ~PCI_MSIX_FLAGS_BIRMASK;
>          dev->msix_table_addr = pci_region[bar_nr].base_addr + 
> msix_table_entry;
> -        dev->msix_max = pci_get_word(pci_dev->config + pos + PCI_MSIX_FLAGS);
> -        dev->msix_max &= PCI_MSIX_FLAGS_QSIZE;
> -        dev->msix_max += 1;
> +        dev->msix_max = msix_max;
>      }
>  
>      /* Minimal PM support, nothing writable, device appears to NAK changes */