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Re: [Qemu-devel] How many msi-x vectors should be allocated for the virt


From: Michael S. Tsirkin
Subject: Re: [Qemu-devel] How many msi-x vectors should be allocated for the virtio-serial device?
Date: Wed, 27 Feb 2013 17:15:54 +0200

On Wed, Feb 27, 2013 at 04:51:00PM +0200, Gal Hammer wrote:
> On 27/02/2013 16:03, Michael S. Tsirkin wrote:
> >On Wed, Feb 27, 2013 at 03:46:25PM +0200, Gal Hammer wrote:
> >>On 27/02/2013 15:28, Paolo Bonzini wrote:
> >>>Il 27/02/2013 14:24, Gal Hammer ha scritto:
> >>>>On 27/02/2013 14:35, Amit Shah wrote:
> >>>>>On (Mon) 04 Feb 2013 [11:59:02], Michael S. Tsirkin wrote:
> >>>>>>On Mon, Feb 04, 2013 at 10:42:32AM +0100, Paolo Bonzini wrote:
> >>>>>>>Il 03/02/2013 13:11, Michael S. Tsirkin ha scritto:
> >>>>>>>>>>   static Property virtio_serial_properties[] = {
> >>>>>>>>>>       DEFINE_PROP_BIT("ioeventfd", VirtIOPCIProxy, flags,
> >>>>>>>>>>VIRTIO_PCI_FLAG_USE_IOEVENTFD_BIT, true),
> >>>>>>>>>>-    DEFINE_PROP_UINT32("vectors", VirtIOPCIProxy, nvectors,
> >>>>>>>>>>DEV_NVECTORS_UNSPECIFIED),
> >>>>>>>>>>+    DEFINE_PROP_UINT32("vectors", VirtIOPCIProxy, nvectors, 2),
> >>>>>>>>>>       DEFINE_PROP_HEX32("class", VirtIOPCIProxy, class_code, 0),
> >>>>>>>>>>       DEFINE_VIRTIO_COMMON_FEATURES(VirtIOPCIProxy, host_features),
> >>>>>>>>>>       DEFINE_PROP_UINT32("max_ports", VirtIOPCIProxy,
> >>>>>>>>>>serial.max_virtserial_ports, 31),
> >>>>>>>>>>
> >>>>>>>>>>plus the backwards-compatibility stuff.
> >>>>>>>>>>
> >>>>>>>>>>Paolo
> >>>>>>>>Makes sense, but the logic in virtio_serial_init_pci is
> >>>>>>>>then dead code and should go away.
> >>>>>>>>
> >>>>>>>
> >>>>>>>It won't be dead code for the backwards-compatible machine types (that
> >>>>>>>use DEV_NVECTORS_UNSPECIFIED).
> >>>>>>>
> >>>>>>>Paolo
> >>>>>>
> >>>>>>Good point. Ack. Want to post this with proper signature etc?
> >>>>>
> >>>>>Gal, do you want to submit a patch for this?
> >>>>>
> >>>>>         Amit
> >>>>>
> >>>>
> >>>>Attached.
> >>>
> >>>You need to add backwards-compatibility properties in hw/pc.h.
> >>>
> >>>Paolo
> >>>
> >>
> >>I've added the BC property. I hope it is in the right format.
> >>
> >>Thanks,
> >>
> >>     Gal.
> >>
> >
> >>>From db49a36ecc4de5744415357691140fb68df4fae2 Mon Sep 17 00:00:00 2001
> >>From: Gal Hammer <address@hidden>
> >>Date: Wed, 27 Feb 2013 15:15:31 +0200
> >>Subject: [PATCH] Set virtio-serial device to have a default of 2 MSI 
> >>vectors.
> >>
> >>The virtio-serial device is expected to use 2 MSI vectors, one for
> >>control queue and a second shared for all queues.
> >>
> >>Signed-off-by: Gal Hammer <address@hidden>
> >>---
> >>  hw/pc.h         | 4 ++++
> >>  hw/virtio-pci.c | 5 ++++-
> >>  2 files changed, 8 insertions(+), 1 deletion(-)
> >>
> >>diff --git a/hw/pc.h b/hw/pc.h
> >>index da1b102..d63d411 100644
> >>--- a/hw/pc.h
> >>+++ b/hw/pc.h
> >>@@ -216,6 +216,10 @@ int e820_add_entry(uint64_t, uint64_t, uint32_t);
> >>              .driver   = "virtio-blk-pci",\
> >>              .property = "discard_granularity",\
> >>              .value    = stringify(0),\
> >>+   },{\
> >>+            .driver   = "virtio-serial-pci",\
> >>+            .property = "vectors",\
> >>+            .value    = stringify(DEV_NVECTORS_UNSPECIFIED),\
> >>    }
> >>
> >>  #endif
> >>diff --git a/hw/virtio-pci.c b/hw/virtio-pci.c
> >>index a869f53..ba56ab2 100644
> >>--- a/hw/virtio-pci.c
> >>+++ b/hw/virtio-pci.c
> >>@@ -975,6 +975,9 @@ static int virtio_serial_init_pci(PCIDevice *pci_dev)
> >>      if (!vdev) {
> >>          return -1;
> >>      }
> >>+
> >>+    /* backwards-compatibility with machines that were created with
> >>+       DEV_NVECTORS_UNSPECIFIED */
> >>      vdev->nvectors = proxy->nvectors == DEV_NVECTORS_UNSPECIFIED
> >>                                          ? 
> >> proxy->serial.max_virtserial_ports + 1
> >>                                          : proxy->nvectors;
> >>@@ -1155,7 +1158,7 @@ static const TypeInfo virtio_net_info = {
> >>
> >>  static Property virtio_serial_properties[] = {
> >>      DEFINE_PROP_BIT("ioeventfd", VirtIOPCIProxy, flags, 
> >> VIRTIO_PCI_FLAG_USE_IOEVENTFD_BIT, true),
> >>-    DEFINE_PROP_UINT32("vectors", VirtIOPCIProxy, nvectors, 
> >>DEV_NVECTORS_UNSPECIFIED),
> >>+    DEFINE_PROP_UINT32("vectors", VirtIOPCIProxy, nvectors, 2),
> >>      DEFINE_PROP_HEX32("class", VirtIOPCIProxy, class_code, 0),
> >>      DEFINE_VIRTIO_COMMON_FEATURES(VirtIOPCIProxy, host_features),
> >>      DEFINE_PROP_UINT32("max_ports", VirtIOPCIProxy, 
> >> serial.max_virtserial_ports, 31),
> >>--
> >>1.8.1.2
> >>
> >
> >
> >Looks good but just making sure - you did test with compat machine type,
> >yes?
> >
> 
> After a small fix (attached), I've executed:
> 
> $ x86_64-softmmu/qemu-system-x86_64 -device virtio-serial-pci
> vectors = 2
> 
> $ x86_64-softmmu/qemu-system-x86_64 -device virtio-serial-pci -M pc-0.14
> vectors = 32
> 
> Is this test is enough?
> 
>     Gal.
> 

You'll want to test 1.4 I guess?


> >From fddf3136cc2cd0372c52a09424715b15c6ad131f Mon Sep 17 00:00:00 2001
> From: Gal Hammer <address@hidden>
> Date: Wed, 27 Feb 2013 15:15:31 +0200
> Subject: [PATCH] Set virtio-serial device to have a default of 2 MSI vectors.
> 
> The virtio-serial device is expected to use 2 MSI vectors, one for
> control queue and a second shared for all queues.
> 
> Signed-off-by: Gal Hammer <address@hidden>
> ---
>  hw/pc.h         | 5 +++++
>  hw/virtio-pci.c | 5 ++++-
>  2 files changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/pc.h b/hw/pc.h
> index da1b102..f2c1b1c 100644
> --- a/hw/pc.h
> +++ b/hw/pc.h
> @@ -216,6 +216,11 @@ int e820_add_entry(uint64_t, uint64_t, uint32_t);
>              .driver   = "virtio-blk-pci",\
>              .property = "discard_granularity",\
>              .value    = stringify(0),\
> +     },{\
> +            .driver   = "virtio-serial-pci",\
> +            .property = "vectors",\
> +            /* DEV_NVECTORS_UNSPECIFIED as a uint32_t string */\
> +            .value    = stringify(0xFFFFFFFF),\
>       }
>  
>  #endif
> diff --git a/hw/virtio-pci.c b/hw/virtio-pci.c
> index a869f53..ba56ab2 100644
> --- a/hw/virtio-pci.c
> +++ b/hw/virtio-pci.c
> @@ -975,6 +975,9 @@ static int virtio_serial_init_pci(PCIDevice *pci_dev)
>      if (!vdev) {
>          return -1;
>      }
> +
> +    /* backwards-compatibility with machines that were created with
> +       DEV_NVECTORS_UNSPECIFIED */
>      vdev->nvectors = proxy->nvectors == DEV_NVECTORS_UNSPECIFIED
>                                          ? proxy->serial.max_virtserial_ports 
> + 1
>                                          : proxy->nvectors;
> @@ -1155,7 +1158,7 @@ static const TypeInfo virtio_net_info = {
>  
>  static Property virtio_serial_properties[] = {
>      DEFINE_PROP_BIT("ioeventfd", VirtIOPCIProxy, flags, 
> VIRTIO_PCI_FLAG_USE_IOEVENTFD_BIT, true),
> -    DEFINE_PROP_UINT32("vectors", VirtIOPCIProxy, nvectors, 
> DEV_NVECTORS_UNSPECIFIED),
> +    DEFINE_PROP_UINT32("vectors", VirtIOPCIProxy, nvectors, 2),
>      DEFINE_PROP_HEX32("class", VirtIOPCIProxy, class_code, 0),
>      DEFINE_VIRTIO_COMMON_FEATURES(VirtIOPCIProxy, host_features),
>      DEFINE_PROP_UINT32("max_ports", VirtIOPCIProxy, 
> serial.max_virtserial_ports, 31),
> -- 
> 1.8.1.2
> 




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