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Re: [Qemu-devel] [PATCH V7 15/16] virtio-pci: increase the maximum numbe


From: Cornelia Huck
Subject: Re: [Qemu-devel] [PATCH V7 15/16] virtio-pci: increase the maximum number of virtqueues to 513
Date: Thu, 23 Apr 2015 13:24:47 +0200

On Thu, 23 Apr 2015 14:21:48 +0800
Jason Wang <address@hidden> wrote:

> This patch increases the maximum number of virtqueues for pci from 64
> to 513. This will allow booting a virtio-net-pci device with 256 queue
     ^^^

> pairs on recent Linux host (which supports up to 256 tuntap queue pairs).
> 
> To keep migration compatibility, 64 was kept for legacy machine
> types. This is because qemu in fact allows guest to probe the limit of
> virtqueues through trying to set queue_sel. So for legacy machine
> type, we should make sure setting queue_sel to more than 63 won't
> make effect.
> 
> Cc: Paolo Bonzini <address@hidden>
> Cc: Richard Henderson <address@hidden>
> Cc: Michael S. Tsirkin <address@hidden>
> Cc: Alexander Graf <address@hidden>
> Cc: address@hidden
> Signed-off-by: Jason Wang <address@hidden>
> ---
>  hw/i386/pc_piix.c      | 5 +++++
>  hw/i386/pc_q35.c       | 5 +++++
>  hw/ppc/spapr.c         | 5 +++++
>  hw/virtio/virtio-pci.c | 6 +++++-
>  4 files changed, 20 insertions(+), 1 deletion(-)
> 
(...)
> diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> index 7d01500..c510cb7 100644
> --- a/hw/virtio/virtio-pci.c
> +++ b/hw/virtio/virtio-pci.c
> @@ -42,7 +42,11 @@
>   * configuration space */
>  #define VIRTIO_PCI_CONFIG_SIZE(dev)     
> VIRTIO_PCI_CONFIG_OFF(msix_enabled(dev))
> 
> -#define VIRTIO_PCI_QUEUE_MAX 64
> +/* The number was chose to be greater than both the the number of max
> + * vcpus supported by host and the number of max tuntap queues support
> + * by host and also leave some spaces for future.
> + */
> +#define VIRTIO_PCI_QUEUE_MAX 1024
                                ^^^^

I think you need to fixup subject and patch description :)

> 
>  static void virtio_pci_bus_new(VirtioBusState *bus, size_t bus_size,
>                                 VirtIOPCIProxy *dev);




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