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Re: [Qemu-devel] [PATCH for-4.2 v10 14/15] virtio-iommu-pci: Add virtio


From: Auger Eric
Subject: Re: [Qemu-devel] [PATCH for-4.2 v10 14/15] virtio-iommu-pci: Add virtio iommu pci support
Date: Wed, 4 Sep 2019 16:19:33 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0

Hi Michael,

On 9/1/19 8:40 AM, Michael S. Tsirkin wrote:
> On Thu, Aug 01, 2019 at 03:49:37PM +0200, Auger Eric wrote:
>> Hi Michael,
>>
>> On 8/1/19 3:06 PM, Michael S. Tsirkin wrote:
>>> On Thu, Aug 01, 2019 at 02:15:03PM +0200, Auger Eric wrote:
>>>> Hi Michael,
>>>>
>>>> On 7/30/19 9:35 PM, Michael S. Tsirkin wrote:
>>>>> On Tue, Jul 30, 2019 at 07:21:36PM +0200, Eric Auger wrote:
>>>>>> This patch adds virtio-iommu-pci, which is the pci proxy for
>>>>>> the virtio-iommu device.
>>>>>>
>>>>>> Signed-off-by: Eric Auger <address@hidden>
>>>>>
>>>>> This part I'm not sure we should merge just yet.  The reason being I
>>>>> think we should limit it to mmio where DT can be used to describe iommu
>>>>> topology. For PCI I don't see why we shouldn't always expose this
>>>>> in the config space, and I think it's preferable not to
>>>>> need to support a mix of DT,ACPI and PCI as options.
>>>>
>>>> For context, some discussion related to this topic already arose on v7
>>>> revision of the driver:
>>>>
>>>> [1] Re: [PATCH v7 0/7] Add virtio-iommu driver
>>>> https://lore.kernel.org/linux-pci/87a7ioby9u.fsf@morokweng.localdomain/
>>>>
>>>> Some additional thoughts.
>>>>
>>>> First considering DT boot.
>>>>
>>>> THE DT description features an iommu-map property in the
>>>> pci-host-ecam-generic node that describes which RIDs are handled by the
>>>> virtio-iommu and a possible offset/mask to be applied inbetween the RID
>>>> and the streamID at the input of the IOMMU
>>>> (Documentation/devicetree/bindings/pci/pci-iommu.txt)
>>>>
>>>> As far as I understand when a DMA capable device is setup, its DMA
>>>> configuration is built using that call chain:
>>>>
>>>> pci_dma_configure
>>>> |_ of_dma_configure
>>>>    |_ of_iommu_configure
>>>>       |_ of_pci_iommu_init
>>>>          |_ of_map_rid
>>>>
>>>> I understand you would like the iommu-map/iommu-map-mask info to be
>>>> exposed directly into the config space of the device instead of inside
>>>> the DT or IORT table. Assuming a module is initialized sufficiently
>>>> early to retrieve this info, we would need the resulting info to be
>>>> consolidated to allow pci_dma_configure chain to work seemlessly. This
>>>> sounds a significant impact on above kernel infrastructure.
>>>
>>> I don't really know what consolidated means.
>>> It is pretty common for IOMMUs to expose config through
>>> PCI registers. This typically happens as a fixup.
>> I meant: instead of retrieving the info through the of_* code you need
>> to interoperate with the module to retrieve the same info and detect
>> when you need to take that path instead of the of one.
> 
> The way to do it would be with a quirk,
> and the quirk would not be part of the
> virtio module - it can poke at the device using
> virtio_pci_cfg_cap.

I got this preliminary quirk function working. However it only works for
a DECLARE_PCI_FIXUP_ENABLE quirk. In an EARLY quirk, the guest crashes
on the first ioread that attempts to read the BAR as mem accesses are
not enabled yet I guess.

So assuming I get the proper system config data in the device
configuration, the iommu bindings will be set up late.

By the way I have not yet attempted to generate iommu bindings from the
quirk function (job done in drivers/acpi/arm64/iort.c) which does not
sound to be straightforward.
> 
>>>
>>> I would write a tiny driver to do exactly that,
>>> and run it from the fixup.
>>>
>>>
>>>> This comes in addition to the development of the "small module that
>>>> loads early and pokes at the IOMMU sufficiently to get the data about
>>>> which devices use the IOMMU out of it using standard virtio config
>>>> space" evoked in [1] + the definition of the data formats to be put in
>>>> the very cfg space.
>>>
>>> That last part is true but that's exactly why I propose we
>>> wait on this patch a bit.
>>>
>>>> With ACPI I understand we have the same kind of infrastructure:
>>>> drivers/acpi/arm64/iort.c currently extracts the mapping between RC RIDs
>>>> and IOMMU streamids
>>>>
>>>> pci_dma_configure(
>>>> |_ acpi_dma_configure
>>>>    |_ iort_iommu_configure
>>>>       |_ iort_pci_iommu_init
>>>>          |_ iort_node_map_id
>>>>             |_ iort_id_map
>>>>
>>>> Maybe I fail to see the easy and right way to do the integration at
>>>> kernel level but I am a bit frightened by the efforts that would be
>>>> requested to follow your suggestion, whereas the DT infra is ready and
>>>> fully upstreamed to accept the use case.
>>>
>>> Did you take a look at drivers/pci/quirks.c and how these run?
>>> I think it's just a question of adding DECLARE_PCI_FIXUP_CLASS_EARLY
>>> and running your hook from there.
>> I will do and trace the code.
>>>
>>>
>>>> For ACPI I agree AFAIK IORT was primarily defined by ARM, for ARM but we
>>>> prototyped IORT integration with x86 and it worked for pc machine
>>>> without major trouble.
>>>>
>>>> I sent the kernel and qemu patches prototyping this IORT integration:
>>>>
>>>> https://github.com/eauger/linux/tree/virtio-iommu-v0.9-iort-x86
>>>> https://github.com/eauger/qemu/tree/v3.1.0-rc3-virtio-iommu-v0.9-x86
>>>>
>>>> There ACPI IORT was built for PC machine and the integration effort at
>>>> both kernel and QEMU level was low. This work would need to be rebased
>>>> and depends on kernel ACPI related patches that are not yet upstreamed
>>>> though.
>>>>
>>>> Thanks
>>>>
>>>> Eric
>>>
>>> In the end it might turn out you are right.  But it does us no harm to
>>> delay this just a bit, and for now limit things to ARM where it's
>>> already used and where alternatives exist.
>> So if my understanding is correct, at the moment you would accept a DT
>> integration using MMIO. Is that correct? Meanwhile we can prototype your
>> suggestion.
>>
>> Thanks
>>
>> Eric
> 
> Right.

Thank you for the confirmation. However I am not sure Peter will accept
to get the device integrated as a virtio-mmio device and then deprecated
in favor of a virtio-pci device, all the more so work was prepared to
get a PCI integration. Peter?

Thanks

Eric
> 
>>>
>>>
>>>>>
>>>>>> ---
>>>>>>
>>>>>> v8 -> v9:
>>>>>> - add the msi-bypass property
>>>>>> - create virtio-iommu-pci.c
>>>>>> ---
>>>>>>  hw/virtio/Makefile.objs          |  1 +
>>>>>>  hw/virtio/virtio-iommu-pci.c     | 88 ++++++++++++++++++++++++++++++++
>>>>>>  include/hw/pci/pci.h             |  1 +
>>>>>>  include/hw/virtio/virtio-iommu.h |  1 +
>>>>>>  qdev-monitor.c                   |  1 +
>>>>>>  5 files changed, 92 insertions(+)
>>>>>>  create mode 100644 hw/virtio/virtio-iommu-pci.c
>>>>>>
>>>>>> diff --git a/hw/virtio/Makefile.objs b/hw/virtio/Makefile.objs
>>>>>> index f42e4dd94f..80ca719f1c 100644
>>>>>> --- a/hw/virtio/Makefile.objs
>>>>>> +++ b/hw/virtio/Makefile.objs
>>>>>> @@ -27,6 +27,7 @@ obj-$(CONFIG_VIRTIO_INPUT_HOST) += 
>>>>>> virtio-input-host-pci.o
>>>>>>  obj-$(CONFIG_VIRTIO_INPUT) += virtio-input-pci.o
>>>>>>  obj-$(CONFIG_VIRTIO_RNG) += virtio-rng-pci.o
>>>>>>  obj-$(CONFIG_VIRTIO_BALLOON) += virtio-balloon-pci.o
>>>>>> +obj-$(CONFIG_VIRTIO_IOMMU) += virtio-iommu-pci.o
>>>>>>  obj-$(CONFIG_VIRTIO_9P) += virtio-9p-pci.o
>>>>>>  obj-$(CONFIG_VIRTIO_SCSI) += virtio-scsi-pci.o
>>>>>>  obj-$(CONFIG_VIRTIO_BLK) += virtio-blk-pci.o
>>>>>> diff --git a/hw/virtio/virtio-iommu-pci.c b/hw/virtio/virtio-iommu-pci.c
>>>>>> new file mode 100644
>>>>>> index 0000000000..f9977096bd
>>>>>> --- /dev/null
>>>>>> +++ b/hw/virtio/virtio-iommu-pci.c
>>>>>> @@ -0,0 +1,88 @@
>>>>>> +/*
>>>>>> + * Virtio IOMMU PCI Bindings
>>>>>> + *
>>>>>> + * Copyright (c) 2019 Red Hat, Inc.
>>>>>> + * Written by Eric Auger
>>>>>> + *
>>>>>> + *  This program is free software; you can redistribute it and/or modify
>>>>>> + *  it under the terms of the GNU General Public License version 2 or
>>>>>> + *  (at your option) any later version.
>>>>>> + */
>>>>>> +
>>>>>> +#include "qemu/osdep.h"
>>>>>> +
>>>>>> +#include "virtio-pci.h"
>>>>>> +#include "hw/virtio/virtio-iommu.h"
>>>>>> +
>>>>>> +typedef struct VirtIOIOMMUPCI VirtIOIOMMUPCI;
>>>>>> +
>>>>>> +/*
>>>>>> + * virtio-iommu-pci: This extends VirtioPCIProxy.
>>>>>> + *
>>>>>> + */
>>>>>> +#define VIRTIO_IOMMU_PCI(obj) \
>>>>>> +        OBJECT_CHECK(VirtIOIOMMUPCI, (obj), TYPE_VIRTIO_IOMMU_PCI)
>>>>>> +
>>>>>> +struct VirtIOIOMMUPCI {
>>>>>> +    VirtIOPCIProxy parent_obj;
>>>>>> +    VirtIOIOMMU vdev;
>>>>>> +};
>>>>>> +
>>>>>> +static Property virtio_iommu_pci_properties[] = {
>>>>>> +    DEFINE_PROP_UINT32("class", VirtIOPCIProxy, class_code, 0),
>>>>>> +    DEFINE_PROP_BOOL("msi-bypass", VirtIOIOMMUPCI, vdev.msi_bypass, 
>>>>>> true),
>>>>>> +    DEFINE_PROP_END_OF_LIST(),
>>>>>> +};
>>>>>> +
>>>>>> +static void virtio_iommu_pci_realize(VirtIOPCIProxy *vpci_dev, Error 
>>>>>> **errp)
>>>>>> +{
>>>>>> +    VirtIOIOMMUPCI *dev = VIRTIO_IOMMU_PCI(vpci_dev);
>>>>>> +    DeviceState *vdev = DEVICE(&dev->vdev);
>>>>>> +
>>>>>> +    qdev_set_parent_bus(vdev, BUS(&vpci_dev->bus));
>>>>>> +    object_property_set_link(OBJECT(dev),
>>>>>> +                             OBJECT(pci_get_bus(&vpci_dev->pci_dev)),
>>>>>> +                             "primary-bus", errp);
>>>>>> +    object_property_set_bool(OBJECT(vdev), true, "realized", errp);
>>>>>> +}
>>>>>> +
>>>>>> +static void virtio_iommu_pci_class_init(ObjectClass *klass, void *data)
>>>>>> +{
>>>>>> +    DeviceClass *dc = DEVICE_CLASS(klass);
>>>>>> +    VirtioPCIClass *k = VIRTIO_PCI_CLASS(klass);
>>>>>> +    PCIDeviceClass *pcidev_k = PCI_DEVICE_CLASS(klass);
>>>>>> +    k->realize = virtio_iommu_pci_realize;
>>>>>> +    set_bit(DEVICE_CATEGORY_MISC, dc->categories);
>>>>>> +    dc->props = virtio_iommu_pci_properties;
>>>>>> +    pcidev_k->vendor_id = PCI_VENDOR_ID_REDHAT_QUMRANET;
>>>>>> +    pcidev_k->device_id = PCI_DEVICE_ID_VIRTIO_IOMMU;
>>>>>> +    pcidev_k->revision = VIRTIO_PCI_ABI_VERSION;
>>>>>> +    pcidev_k->class_id = PCI_CLASS_OTHERS;
>>>>>> +}
>>>>>> +
>>>>>> +static void virtio_iommu_pci_instance_init(Object *obj)
>>>>>> +{
>>>>>> +    VirtIOIOMMUPCI *dev = VIRTIO_IOMMU_PCI(obj);
>>>>>> +
>>>>>> +    virtio_instance_init_common(obj, &dev->vdev, sizeof(dev->vdev),
>>>>>> +                                TYPE_VIRTIO_IOMMU);
>>>>>> +}
>>>>>> +
>>>>>> +static const VirtioPCIDeviceTypeInfo virtio_iommu_pci_info = {
>>>>>> +    .base_name             = TYPE_VIRTIO_IOMMU_PCI,
>>>>>> +    .generic_name          = "virtio-iommu-pci",
>>>>>> +    .transitional_name     = "virtio-iommu-pci-transitional",
>>>>>> +    .non_transitional_name = "virtio-iommu-pci-non-transitional",
>>>>>> +    .instance_size = sizeof(VirtIOIOMMUPCI),
>>>>>> +    .instance_init = virtio_iommu_pci_instance_init,
>>>>>> +    .class_init    = virtio_iommu_pci_class_init,
>>>>>> +};
>>>>>> +
>>>>>> +static void virtio_iommu_pci_register(void)
>>>>>> +{
>>>>>> +    virtio_pci_types_register(&virtio_iommu_pci_info);
>>>>>> +}
>>>>>> +
>>>>>> +type_init(virtio_iommu_pci_register)
>>>>>> +
>>>>>> +
>>>>>> diff --git a/include/hw/pci/pci.h b/include/hw/pci/pci.h
>>>>>> index aaf1b9f70d..492ea7e68d 100644
>>>>>> --- a/include/hw/pci/pci.h
>>>>>> +++ b/include/hw/pci/pci.h
>>>>>> @@ -86,6 +86,7 @@ extern bool pci_available;
>>>>>>  #define PCI_DEVICE_ID_VIRTIO_9P          0x1009
>>>>>>  #define PCI_DEVICE_ID_VIRTIO_VSOCK       0x1012
>>>>>>  #define PCI_DEVICE_ID_VIRTIO_PMEM        0x1013
>>>>>> +#define PCI_DEVICE_ID_VIRTIO_IOMMU       0x1014
>>>>>>  
>>>>>>  #define PCI_VENDOR_ID_REDHAT             0x1b36
>>>>>>  #define PCI_DEVICE_ID_REDHAT_BRIDGE      0x0001
>>>>>> diff --git a/include/hw/virtio/virtio-iommu.h 
>>>>>> b/include/hw/virtio/virtio-iommu.h
>>>>>> index 56c8b4e57f..893ac65c0b 100644
>>>>>> --- a/include/hw/virtio/virtio-iommu.h
>>>>>> +++ b/include/hw/virtio/virtio-iommu.h
>>>>>> @@ -25,6 +25,7 @@
>>>>>>  #include "hw/pci/pci.h"
>>>>>>  
>>>>>>  #define TYPE_VIRTIO_IOMMU "virtio-iommu-device"
>>>>>> +#define TYPE_VIRTIO_IOMMU_PCI "virtio-iommu-device-base"
>>>>>>  #define VIRTIO_IOMMU(obj) \
>>>>>>          OBJECT_CHECK(VirtIOIOMMU, (obj), TYPE_VIRTIO_IOMMU)
>>>>>>  
>>>>>> diff --git a/qdev-monitor.c b/qdev-monitor.c
>>>>>> index 58222c2211..74cf090c61 100644
>>>>>> --- a/qdev-monitor.c
>>>>>> +++ b/qdev-monitor.c
>>>>>> @@ -63,6 +63,7 @@ static const QDevAlias qdev_alias_table[] = {
>>>>>>      { "virtio-input-host-ccw", "virtio-input-host", QEMU_ARCH_S390X },
>>>>>>      { "virtio-input-host-pci", "virtio-input-host",
>>>>>>              QEMU_ARCH_ALL & ~QEMU_ARCH_S390X },
>>>>>> +    { "virtio-iommu-pci", "virtio-iommu", QEMU_ARCH_ALL & 
>>>>>> ~QEMU_ARCH_S390X },
>>>>>>      { "virtio-keyboard-ccw", "virtio-keyboard", QEMU_ARCH_S390X },
>>>>>>      { "virtio-keyboard-pci", "virtio-keyboard",
>>>>>>              QEMU_ARCH_ALL & ~QEMU_ARCH_S390X },
>>>>>> -- 
>>>>>> 2.20.1
>>>>>
>>>



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