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

[Auger Eric]

Hi Markus,
On 6/25/20 9:05 AM, Markus Armbruster wrote:
> 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!
OK I will do.
> 
> Can I trigger the assertion with -device?  My try to find the answer
> myself failed:
At the moment the virtio-iommu-pci device only can be instantiated with
machvirt, booting in dt mode.
> 
>     $ 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/.

Thanks

Eric
> 
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