> Am 08.04.2015 um 10:10 schrieb Jason Wang <jasow...@redhat.com>:
>
>
>
>> On 04/08/2015 12:54 AM, Alexander Graf wrote:
>>> On 04/01/2015 10:15 AM, Jason Wang 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.
>>>
>>> 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 <pbonz...@redhat.com>
>>> Cc: Richard Henderson <r...@twiddle.net>
>>> Cc: Michael S. Tsirkin <m...@redhat.com>
>>> Cc: Alexander Graf <ag...@suse.de>
>>> Cc: qemu-...@nongnu.org
>>> Signed-off-by: Jason Wang <jasow...@redhat.com>
>>> ---
>>> hw/i386/pc_piix.c | 5 +++++
>>> hw/i386/pc_q35.c | 5 +++++
>>> hw/ppc/spapr.c | 5 +++++
>>> hw/virtio/virtio-pci.c | 2 +-
>>> 4 files changed, 16 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
>>> index 212e263..6e098ce 100644
>>> --- a/hw/i386/pc_piix.c
>>> +++ b/hw/i386/pc_piix.c
>>> @@ -49,6 +49,7 @@
>>> #include "hw/acpi/acpi.h"
>>> #include "cpu.h"
>>> #include "qemu/error-report.h"
>>> +#include "hw/virtio/virtio-bus.h"
>>> #ifdef CONFIG_XEN
>>> # include <xen/hvm/hvm_info_table.h>
>>> #endif
>>> @@ -312,6 +313,10 @@ static void pc_init_pci(MachineState *machine)
>>> static void pc_compat_2_3(MachineState *machine)
>>> {
>>> + ObjectClass *klass = object_class_by_name("virtio-pci-bus");
>>> + VirtioBusClass *k = VIRTIO_BUS_CLASS(klass);
>>> +
>>> + k->queue_max = 64;
>>> }
>>> static void pc_compat_2_2(MachineState *machine)
>>> diff --git a/hw/i386/pc_q35.c b/hw/i386/pc_q35.c
>>> index e67f2de..ff7c414 100644
>>> --- a/hw/i386/pc_q35.c
>>> +++ b/hw/i386/pc_q35.c
>>> @@ -45,6 +45,7 @@
>>> #include "hw/usb.h"
>>> #include "hw/cpu/icc_bus.h"
>>> #include "qemu/error-report.h"
>>> +#include "include/hw/virtio/virtio-bus.h"
>>> /* ICH9 AHCI has 6 ports */
>>> #define MAX_SATA_PORTS 6
>>> @@ -291,6 +292,10 @@ static void pc_q35_init(MachineState *machine)
>>> static void pc_compat_2_3(MachineState *machine)
>>> {
>>> + ObjectClass *klass = object_class_by_name("virtio-pci-bus");
>>> + VirtioBusClass *k = VIRTIO_BUS_CLASS(klass);
>>> +
>>> + k->queue_max = 64;
>>> }
>>> static void pc_compat_2_2(MachineState *machine)
>>> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
>>> index 8e43aa2..ee8f6a3 100644
>>> --- a/hw/ppc/spapr.c
>>> +++ b/hw/ppc/spapr.c
>>> @@ -50,6 +50,7 @@
>>> #include "hw/pci/pci.h"
>>> #include "hw/scsi/scsi.h"
>>> #include "hw/virtio/virtio-scsi.h"
>>> +#include "hw/virtio/virtio-bus.h"
>>> #include "exec/address-spaces.h"
>>> #include "hw/usb.h"
>>> @@ -1827,6 +1828,10 @@ static const TypeInfo spapr_machine_info = {
>>> static void spapr_compat_2_3(Object *obj)
>>> {
>>> + ObjectClass *klass = object_class_by_name("virtio-pci-bus");
>>> + VirtioBusClass *k = VIRTIO_BUS_CLASS(klass);
>>> +
>>> + k->queue_max = 64;
>>> }
>>> static void spapr_compat_2_2(Object *obj)
>>> diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
>>> index 9a5242a..02e3ce8 100644
>>> --- a/hw/virtio/virtio-pci.c
>>> +++ b/hw/virtio/virtio-pci.c
>>> @@ -42,7 +42,7 @@
>>> * configuration space */
>>> #define VIRTIO_PCI_CONFIG_SIZE(dev)
>>> VIRTIO_PCI_CONFIG_OFF(msix_enabled(dev))
>>> -#define VIRTIO_PCI_QUEUE_MAX 64
>>> +#define VIRTIO_PCI_QUEUE_MAX 513
>>
>> 513 is an interesting number. Any particular reason for it? Maybe this
>> was mentioned before and I just missed it ;)
>>
>>
>> Alex
>
> The number were chose to match kernel limit for tuntap queues. Recent
> kernel allow up to 256 queues for tuntap, so 513 is in fact 256 * 2 plus
> 1 control vq.
I see. I'm not fully convinced that it's a good idea to bake that limit into
qemu, but we have to have a limit somewhere.
However, could you please make it more obvious in the code where thid number
stems from? Either by using defines or with a comment.
Alex
