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Re: [Qemu-devel] [PATCH V7 15/16] virtio-pci: increase the maximum numbe
From: |
Michael S. Tsirkin |
Subject: |
Re: [Qemu-devel] [PATCH V7 15/16] virtio-pci: increase the maximum number of virtqueues to 513 |
Date: |
Tue, 28 Apr 2015 09:17:48 +0200 |
On Tue, Apr 28, 2015 at 11:12:10AM +0800, Jason Wang wrote:
>
>
> On Mon, Apr 27, 2015 at 7:02 PM, Michael S. Tsirkin <address@hidden> wrote:
> >On Thu, Apr 23, 2015 at 02:21:48PM +0800, 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 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.
> >
> >This isn't a documented interface, and no guest that I know of does
> >this. Accordingly, I think we should drop everything except the
> >hw/virtio/virtio-pci.c change.
>
> We leave a chance for guest to use such undocumented behavior, so
> technically we'd better keep it and it maybe too late for us to fix if we
> find such a guest in the future. And consider keeping this compatibility was
> really not hard, so I suggest to include this.
Reminds me of https://xkcd.com/1172/
We don't do this kind of thing.
> >
> >
> >> 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/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 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
> >> static void virtio_pci_bus_new(VirtioBusState *bus, size_t
> >>bus_size,
> >> VirtIOPCIProxy *dev);
> >> -- 2.1.0
- [Qemu-devel] [PATCH V7 11/16] virtio-mmio: switch to bus specific queue limit, (continued)
- [Qemu-devel] [PATCH V7 11/16] virtio-mmio: switch to bus specific queue limit, Jason Wang, 2015/04/23
- [Qemu-devel] [PATCH V7 10/16] virtio-s390: switch to bus specific queue limit, Jason Wang, 2015/04/23
- [Qemu-devel] [PATCH V7 12/16] virtio-pci: switch to use bus specific queue limit, Jason Wang, 2015/04/23
- [Qemu-devel] [PATCH V7 13/16] virtio: introduce vector to virtqueues mapping, Jason Wang, 2015/04/23
- [Qemu-devel] [PATCH V7 14/16] virtio-pci: speedup MSI-X masking and unmasking, Jason Wang, 2015/04/23
- [Qemu-devel] [PATCH V7 15/16] virtio-pci: increase the maximum number of virtqueues to 513, Jason Wang, 2015/04/23
- [Qemu-devel] [PATCH V7 16/16] pci: remove hard-coded bar size in msix_init_exclusive_bar(), Jason Wang, 2015/04/23
- Re: [Qemu-devel] [PATCH V7 00/16] Support more virtio queues, Cornelia Huck, 2015/04/23
- Re: [Qemu-devel] [PATCH V7 00/16] Support more virtio queues, Michael S. Tsirkin, 2015/04/27