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Re: [Qemu-devel] [PATCH V2] hw/virtio-pci: fix virtio behaviour on moder
From: |
Michael S. Tsirkin |
Subject: |
Re: [Qemu-devel] [PATCH V2] hw/virtio-pci: fix virtio behaviour on modern (PCIe) machines |
Date: |
Wed, 20 Jul 2016 01:56:16 +0300 |
On Tue, Jul 19, 2016 at 09:42:58PM +0300, Marcel Apfelbaum wrote:
> Modern machines are expected to be used by newer setups with
> modern guests aiming the use of the latest features.
>
> Enable modern and disable legacy for virtio devices
> plugged into PCIe ports (Root ports or Downstream ports).
> Using the Virtio 1 mode will remove the limitation
> of the number of devices that can be attached to a machine
> by removing the need for the IO BAR.
>
> Convert 'disable-modern' and 'disable-legacy' properties to OnOffAuto
> with default Auto.
>
> Signed-off-by: Marcel Apfelbaum <address@hidden>
> ---
>
> Hi,
>
> v1 -> v2:
> - Stick to existing defaults for old machine types (Michael S. Tsirkin)
>
> If everyone agrees, I am thinking about getting it into 2.7
> to avoid the ~15 virtio devices limitation per machine.
>
> Notes:
> - The non PCIe machines behaviour should remain the same.
> - I hope is OK to make the disable-* properties OnOffAuto. Previous setups
> using them can be affected,
why? could you explain pls? isn't onoffauto compatible with bit
properties?
> but libvirt is not using them yet (as far as I know)
> - My tests were limited to checking all possible disable-* configurations
> (and make check for all archs)
>
> Thanks,
> Marcel
>
> hw/virtio/virtio-pci.c | 31 ++++++++++++++++++++++++-------
> hw/virtio/virtio-pci.h | 2 ++
> include/hw/compat.h | 8 ++++++++
> 3 files changed, 34 insertions(+), 7 deletions(-)
>
> diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> index 2b34b43..ec9e84f 100644
> --- a/hw/virtio/virtio-pci.c
> +++ b/hw/virtio/virtio-pci.c
> @@ -1716,6 +1716,8 @@ static void virtio_pci_realize(PCIDevice *pci_dev,
> Error **errp)
> {
> VirtIOPCIProxy *proxy = VIRTIO_PCI(pci_dev);
> VirtioPCIClass *k = VIRTIO_PCI_GET_CLASS(pci_dev);
> + bool pcie_port = (pci_bus_is_express(pci_dev->bus) &&
> + !pci_bus_is_root(pci_dev->bus));
drop the extra outside () please.
>
> /*
> * virtio pci bar layout used by default.
> @@ -1766,8 +1768,23 @@ static void virtio_pci_realize(PCIDevice *pci_dev,
> Error **errp)
>
> address_space_init(&proxy->modern_as, &proxy->modern_cfg,
> "virtio-pci-cfg-as");
>
> - if (pci_is_express(pci_dev) && pci_bus_is_express(pci_dev->bus) &&
> - !pci_bus_is_root(pci_dev->bus)) {
> + if ((pcie_port && (proxy->disable_modern == ON_OFF_AUTO_AUTO))
> + || (proxy->disable_modern == ON_OFF_AUTO_OFF)) {
drop the () around == - logic and math mix naturally in C.
also, pls put || at end of line, not at the beginning of
continuation. this way you can see there is
continuation as you read the code naturally.
> + proxy->flags &= ~VIRTIO_PCI_FLAG_DISABLE_MODERN;
> + pci_dev->cap_present |= QEMU_PCI_CAP_EXPRESS;
> + } else {
> + proxy->flags |= VIRTIO_PCI_FLAG_DISABLE_MODERN;
> + pci_dev->cap_present &= ~QEMU_PCI_CAP_EXPRESS;
> + }
> +
> + if ((pcie_port && (proxy->disable_legacy == ON_OFF_AUTO_AUTO))
> + || (proxy->disable_legacy == ON_OFF_AUTO_ON)) {
> + proxy->flags |= VIRTIO_PCI_FLAG_DISABLE_LEGACY;
> + } else {
> + proxy->flags &= ~VIRTIO_PCI_FLAG_DISABLE_LEGACY;
> + }
> +
So this is a bit messy.
Can we do:
if (pcie_port)
default_disable_legacy = false;
else
default_disable_legacy = true;
now
if (proxy->disable_legacy == ON_OFF_AUTO_ON ||
(proxy->disable_legacy == ON_OFF_AUTO_AUTO &&
default_disable_legacy))
proxy->flags |= VIRTIO_PCI_FLAG_DISABLE_LEGACY;
else
proxy->flags &= ~VIRTIO_PCI_FLAG_DISABLE_LEGACY;
?
Also, I wonder how does this interact with devices that play with
these flags themselves, like virtio gpu?
I guess we could just set VIRTIO_PCI_FLAG_DISABLE_LEGACY, avoid clearing it.
Setting disable modern might be problematic for same reason, not sure what
to do about that one.
Did I miss anything?
> + if (pcie_port && pci_is_express(pci_dev)) {
> int pos;
>
> pos = pcie_endpoint_cap_init(pci_dev, 0);
> @@ -1821,10 +1838,10 @@ static void virtio_pci_reset(DeviceState *qdev)
> static Property virtio_pci_properties[] = {
> DEFINE_PROP_BIT("virtio-pci-bus-master-bug-migration", VirtIOPCIProxy,
> flags,
> VIRTIO_PCI_FLAG_BUS_MASTER_BUG_MIGRATION_BIT, false),
> - DEFINE_PROP_BIT("disable-legacy", VirtIOPCIProxy, flags,
> - VIRTIO_PCI_FLAG_DISABLE_LEGACY_BIT, false),
> - DEFINE_PROP_BIT("disable-modern", VirtIOPCIProxy, flags,
> - VIRTIO_PCI_FLAG_DISABLE_MODERN_BIT, true),
> + DEFINE_PROP_ON_OFF_AUTO("disable-legacy", VirtIOPCIProxy, disable_legacy,
> + ON_OFF_AUTO_AUTO),
> + DEFINE_PROP_ON_OFF_AUTO("disable-modern", VirtIOPCIProxy, disable_modern,
> + ON_OFF_AUTO_AUTO),
> DEFINE_PROP_BIT("migrate-extra", VirtIOPCIProxy, flags,
> VIRTIO_PCI_FLAG_MIGRATE_EXTRA_BIT, true),
> DEFINE_PROP_BIT("modern-pio-notify", VirtIOPCIProxy, flags,
> @@ -1841,7 +1858,7 @@ static void virtio_pci_dc_realize(DeviceState *qdev,
> Error **errp)
> PCIDevice *pci_dev = &proxy->pci_dev;
>
> if (!(proxy->flags & VIRTIO_PCI_FLAG_DISABLE_PCIE) &&
> - !(proxy->flags & VIRTIO_PCI_FLAG_DISABLE_MODERN)) {
> + !(proxy->disable_modern == ON_OFF_AUTO_ON)) {
> pci_dev->cap_present |= QEMU_PCI_CAP_EXPRESS;
> }
>
> diff --git a/hw/virtio/virtio-pci.h b/hw/virtio/virtio-pci.h
> index e4548c2..4f219d4 100644
> --- a/hw/virtio/virtio-pci.h
> +++ b/hw/virtio/virtio-pci.h
> @@ -144,6 +144,8 @@ struct VirtIOPCIProxy {
> uint32_t modern_mem_bar;
> int config_cap;
> uint32_t flags;
> + OnOffAuto disable_modern;
> + OnOffAuto disable_legacy;
> uint32_t class_code;
> uint32_t nvectors;
> uint32_t dfselect;
> diff --git a/include/hw/compat.h b/include/hw/compat.h
> index 9914e7a..1531399 100644
> --- a/include/hw/compat.h
> +++ b/include/hw/compat.h
> @@ -6,6 +6,14 @@
> .driver = "virtio-mmio",\
> .property = "format_transport_address",\
> .value = "off",\
> + },{\
> + .driver = "virtio-pci",\
> + .property = "disable-modern",\
> + .value = "on",\
> + },{\
> + .driver = "virtio-pci",\
> + .property = "disable-legacy",\
> + .value = "off",\
> },
>
> #define HW_COMPAT_2_5 \
> --
> 2.4.3