Re: [PATCH v3 05/10] pc: Allow instantiating a virtio-iommu device

[Igor Mammedov <imammedo@redhat.com>]

On Tue, 14 Sep 2021 15:20:00 +0100
Jean-Philippe Brucker <jean-philippe@linaro.org> wrote:

> Allow instantiating a virtio-iommu device by adding an ACPI Virtual I/O
> Translation table (VIOT), which describes the relation between the
> virtio-iommu and the endpoints it manages.
> 
> Add a hotplug handler for virtio-iommu on x86 and set the necessary
> reserved region property. On x86, the [0xfee00000, 0xfeefffff] DMA
> region is reserved for MSIs. DMA transactions to this range either
> trigger IRQ remapping in the IOMMU or bypasses IOMMU translation.
> 
> Although virtio-iommu does not support IRQ remapping it must be informed
> of the reserved region so that it can forward DMA transactions targeting
> this region.
> 
> Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
> ---
>  include/hw/i386/pc.h |  2 ++
>  hw/i386/acpi-build.c |  5 +++++
>  hw/i386/pc.c         | 28 +++++++++++++++++++++++++++-
>  hw/i386/Kconfig      |  1 +
>  4 files changed, 35 insertions(+), 1 deletion(-)
> 
> diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
> index 82cf7b7e30..f3ba1ee4c0 100644
> --- a/include/hw/i386/pc.h
> +++ b/include/hw/i386/pc.h
> @@ -45,6 +45,8 @@ typedef struct PCMachineState {
>      bool pit_enabled;
>      bool hpet_enabled;
>      bool default_bus_bypass_iommu;
> +    bool virtio_iommu;
> +    uint16_t virtio_iommu_bdf;
>      uint64_t max_fw_size;
>  
>      /* ACPI Memory hotplug IO base address */
> diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> index 547cd4ed9d..76845026d8 100644
> --- a/hw/i386/acpi-build.c
> +++ b/hw/i386/acpi-build.c
> @@ -71,6 +71,7 @@
>  
>  #include "hw/acpi/ipmi.h"
>  #include "hw/acpi/hmat.h"
> +#include "hw/acpi/viot.h"
>  
>  /* These are used to size the ACPI tables for -M pc-i440fx-1.7 and
>   * -M pc-i440fx-2.0.  Even if the actual amount of AML generated grows
> @@ -2593,6 +2594,10 @@ void acpi_build(AcpiBuildTables *tables, MachineState *machine)
>              build_dmar_q35(tables_blob, tables->linker, x86ms->oem_id,
>                             x86ms->oem_table_id);
>          }
> +    } else if (pcms->virtio_iommu) {
> +        acpi_add_table(table_offsets, tables_blob);
> +        build_viot(tables_blob, tables->linker, pcms->virtio_iommu_bdf,
> +                   x86ms->oem_id, x86ms->oem_table_id);
>      }
>      if (machine->nvdimms_state->is_enabled) {
>          nvdimm_build_acpi(table_offsets, tables_blob, tables->linker,
> diff --git a/hw/i386/pc.c b/hw/i386/pc.c
> index 7e523b913c..a31e950599 100644
> --- a/hw/i386/pc.c
> +++ b/hw/i386/pc.c
> @@ -83,6 +83,7 @@
>  #include "hw/i386/intel_iommu.h"
>  #include "hw/net/ne2000-isa.h"
>  #include "standard-headers/asm-x86/bootparam.h"
> +#include "hw/virtio/virtio-iommu.h"
>  #include "hw/virtio/virtio-pmem-pci.h"
>  #include "hw/virtio/virtio-mem-pci.h"
>  #include "hw/mem/memory-device.h"
> @@ -798,6 +799,11 @@ void pc_machine_done(Notifier *notifier, void *data)
>                       "irqchip support.");
>          exit(EXIT_FAILURE);
>      }
> +
> +    if (pcms->virtio_iommu && x86_iommu_get_default()) {
> +        error_report("QEMU does not support multiple vIOMMUs for x86 yet.");
> +        exit(EXIT_FAILURE);
> +    }

previous patch does similar check, doesn't it?
So is why it's not implement the same way?

>  }
>  
>  void pc_guest_info_init(PCMachineState *pcms)
> @@ -1368,6 +1374,14 @@ static void pc_machine_device_pre_plug_cb(HotplugHandler *hotplug_dev,
>      } else if (object_dynamic_cast(OBJECT(dev), TYPE_VIRTIO_PMEM_PCI) ||
>                 object_dynamic_cast(OBJECT(dev), TYPE_VIRTIO_MEM_PCI)) {
>          pc_virtio_md_pci_pre_plug(hotplug_dev, dev, errp);
> +    } else if (object_dynamic_cast(OBJECT(dev), TYPE_VIRTIO_IOMMU_PCI)) {
> +        /* Declare the reserved MSI region */
> +        char *resv_prop_str = g_strdup_printf("0xfee00000:0xfeefffff:%d",
> +                                              VIRTIO_IOMMU_RESV_MEM_T_MSI);

add a comment describing where these values come from, pls.

> +
> +        qdev_prop_set_uint32(dev, "len-reserved-regions", 1);
> +        qdev_prop_set_string(dev, "reserved-regions[0]", resv_prop_str);

why not use qom setters directly
(they have error argument and can gracefully error out,
which is expected error handling in pre_plug)

and fix up similar (ab)use of setters in virt_machine_device_pre_plug_cb()

> +        g_free(resv_prop_str);
>      }
>  }
>  
> @@ -1381,6 +1395,17 @@ static void pc_machine_device_plug_cb(HotplugHandler *hotplug_dev,
>      } else if (object_dynamic_cast(OBJECT(dev), TYPE_VIRTIO_PMEM_PCI) ||
>                 object_dynamic_cast(OBJECT(dev), TYPE_VIRTIO_MEM_PCI)) {
>          pc_virtio_md_pci_plug(hotplug_dev, dev, errp);
> +    } else if (object_dynamic_cast(OBJECT(dev), TYPE_VIRTIO_IOMMU_PCI)) {
> +        PCMachineState *pcms = PC_MACHINE(hotplug_dev);
> +        PCIDevice *pdev = PCI_DEVICE(dev);
> +
> +        if (pcms->virtio_iommu) {
> +            error_setg(errp,
> +                       "QEMU does not support multiple vIOMMUs for x86 yet.");
> +            return;
> +        }

move to pre_plug please

> +        pcms->virtio_iommu = true;
> +        pcms->virtio_iommu_bdf = pci_get_bdf(pdev);
>      }
>  }
>  
> @@ -1422,7 +1447,8 @@ static HotplugHandler *pc_get_hotplug_handler(MachineState *machine,
>      if (object_dynamic_cast(OBJECT(dev), TYPE_PC_DIMM) ||
>          object_dynamic_cast(OBJECT(dev), TYPE_CPU) ||
>          object_dynamic_cast(OBJECT(dev), TYPE_VIRTIO_PMEM_PCI) ||
> -        object_dynamic_cast(OBJECT(dev), TYPE_VIRTIO_MEM_PCI)) {
> +        object_dynamic_cast(OBJECT(dev), TYPE_VIRTIO_MEM_PCI) ||
> +        object_dynamic_cast(OBJECT(dev), TYPE_VIRTIO_IOMMU_PCI)) {
>          return HOTPLUG_HANDLER(machine);
>      }
>  
> diff --git a/hw/i386/Kconfig b/hw/i386/Kconfig
> index ddedcef0b2..13db05d557 100644
> --- a/hw/i386/Kconfig
> +++ b/hw/i386/Kconfig
> @@ -54,6 +54,7 @@ config PC_ACPI
>      select ACPI_X86
>      select ACPI_CPU_HOTPLUG
>      select ACPI_MEMORY_HOTPLUG
> +    select ACPI_VIOT
>      select SMBUS_EEPROM
>      select PFLASH_CFI01
>      depends on ACPI_SMBUS