Re: [PATCH v5 2/5] virtio-iommu: Implement RESV_MEM probe request

[Markus Armbruster <armbru@redhat.com>]

Eric Auger <eric.auger@redhat.com> writes:

> This patch implements the PROBE request. At the moment,
> only THE RESV_MEM property is handled. The first goal is
> to report iommu wide reserved regions such as the MSI regions
> set by the machine code. On x86 this will be the IOAPIC MSI
> region, [0xFEE00000 - 0xFEEFFFFF], on ARM this may be the ITS
> doorbell.
>
> In the future we may introduce per device reserved regions.
> This will be useful when protecting host assigned devices
> which may expose their own reserved regions
>
> Signed-off-by: Eric Auger <eric.auger@redhat.com>
> Reviewed-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
>
> ---
>
> v4 -> v5:
> - assert if reserved region type is different from RESERVED or
>   MSI
>
> v3 -> v4:
> - removed any reference to the NONE property that does not
>   exist anymore.
>
> v2 -> v3:
> - on probe, do not fill the reminder of the buffer with zeroes
>   as the buffer was already zero initialized (Bharat)
>
> v1 -> v2:
> - move the unlock back to the same place
> - remove the push label and factorize the code after the out label
> - fix a bunch of cpu_to_leX according to the latest spec revision
> - do not remove sizeof(last) from free space
> - check the ep exists
> ---
>  include/hw/virtio/virtio-iommu.h |  2 +
>  hw/virtio/virtio-iommu.c         | 92 ++++++++++++++++++++++++++++++--
>  hw/virtio/trace-events           |  1 +
>  3 files changed, 91 insertions(+), 4 deletions(-)
>
> diff --git a/include/hw/virtio/virtio-iommu.h b/include/hw/virtio/virtio-iommu.h
> index e653004d7c..49eb105cd8 100644
> --- a/include/hw/virtio/virtio-iommu.h
> +++ b/include/hw/virtio/virtio-iommu.h
> @@ -53,6 +53,8 @@ typedef struct VirtIOIOMMU {
>      GHashTable *as_by_busptr;
>      IOMMUPciBus *iommu_pcibus_by_bus_num[PCI_BUS_MAX];
>      PCIBus *primary_bus;
> +    ReservedRegion *reserved_regions;
> +    uint32_t nb_reserved_regions;
>      GTree *domains;
>      QemuMutex mutex;
>      GTree *endpoints;
> diff --git a/hw/virtio/virtio-iommu.c b/hw/virtio/virtio-iommu.c
> index 483883ec1d..aabc3e36b1 100644
> --- a/hw/virtio/virtio-iommu.c
> +++ b/hw/virtio/virtio-iommu.c
> @@ -38,6 +38,7 @@
>  
>  /* Max size */
>  #define VIOMMU_DEFAULT_QUEUE_SIZE 256
> +#define VIOMMU_PROBE_SIZE 512
>  
>  typedef struct VirtIOIOMMUDomain {
>      uint32_t id;
> @@ -378,6 +379,63 @@ static int virtio_iommu_unmap(VirtIOIOMMU *s,
>      return ret;
>  }
>  
> +static ssize_t virtio_iommu_fill_resv_mem_prop(VirtIOIOMMU *s, uint32_t ep,
> +                                               uint8_t *buf, size_t free)
> +{
> +    struct virtio_iommu_probe_resv_mem prop = {};
> +    size_t size = sizeof(prop), length = size - sizeof(prop.head), total;
> +    int i;
> +
> +    total = size * s->nb_reserved_regions;
> +
> +    if (total > free) {
> +        return -ENOSPC;
> +    }
> +
> +    for (i = 0; i < s->nb_reserved_regions; i++) {
> +        prop.head.type = cpu_to_le16(VIRTIO_IOMMU_PROBE_T_RESV_MEM);
> +        prop.head.length = cpu_to_le16(length);
> +        prop.subtype = s->reserved_regions[i].type;
> +        assert(prop.subtype == VIRTIO_IOMMU_RESV_MEM_T_RESERVED ||
> +               prop.subtype == VIRTIO_IOMMU_RESV_MEM_T_MSI);

The assertion makes sense here: we're mapping from the generic
ReservedRegion type (which is unsigned) to the specific
virtio_iommu_probe_resv_mem subtype (which is uint8_t, but only these
two values are valid).

Howver, the assertion should test s->reserved_regions[i].type and go
before the assignment, to ensure it doesn't truncate!

Can I trigger the assertion with -device?  My try to find the answer
myself failed:

    $ qemu-system-x86_64 -nodefaults -S -display none -device virtio-iommu-pci,len-reserved-regions=1,reserved-regions[0]=0xfee00000:0xfeefffff:99
    qemu-system-x86_64: -device virtio-iommu-pci,len-reserved-regions=1,reserved-regions[0]=0xfee00000:0xfeefffff:99: pc-i440fx-5.1 machine fails to create iommu-map device tree bindings
    Check you machine implements a hotplug handler for the virtio-iommu-pci device
    Check the guest is booted without FW or with -no-acpi

By the way: s/Check you machine/Check your machine/.

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