RE: [PATCH v3 05/19] backends/host_iommu_device: Introduce HostIOMMUDeviceCaps

[Duan, Zhenzhong]

>-----Original Message-----
>From: Cédric Le Goater <clg@redhat.com>
>Subject: Re: [PATCH v3 05/19] backends/host_iommu_device: Introduce
>HostIOMMUDeviceCaps
>
>On 4/29/24 08:50, Zhenzhong Duan wrote:
>> HostIOMMUDeviceCaps's elements map to the host IOMMU's capabilities.
>> Different platform IOMMU can support different elements.
>>
>> Currently only two elements, type and aw_bits, type hints the host
>> platform IOMMU type, i.e., INTEL vtd, ARM smmu, etc; aw_bits hints
>> host IOMMU address width.
>>
>> Introduce .check_cap() handler to check if
>HOST_IOMMU_DEVICE_CAP_XXX
>> is supported.
>>
>> Introduce a HostIOMMUDevice API host_iommu_device_check_cap()
>which
>> is a wrapper of .check_cap().
>>
>> Introduce a HostIOMMUDevice API
>host_iommu_device_check_cap_common()
>> to check common capabalities of different host platform IOMMUs.
>>
>> Suggested-by: Cédric Le Goater <clg@redhat.com>
>> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
>> ---
>>   include/sysemu/host_iommu_device.h | 44
>++++++++++++++++++++++++++++++
>>   backends/host_iommu_device.c       | 29 ++++++++++++++++++++
>>   2 files changed, 73 insertions(+)
>>
>> diff --git a/include/sysemu/host_iommu_device.h
>b/include/sysemu/host_iommu_device.h
>> index 2b58a94d62..12b6afb463 100644
>> --- a/include/sysemu/host_iommu_device.h
>> +++ b/include/sysemu/host_iommu_device.h
>> @@ -14,12 +14,27 @@
>>
>>   #include "qom/object.h"
>>   #include "qapi/error.h"
>> +#include "linux/iommufd.h"
>> +
>> +/**
>> + * struct HostIOMMUDeviceCaps - Define host IOMMU device capabilities.
>> + *
>> + * @type: host platform IOMMU type.
>> + *
>> + * @aw_bits: host IOMMU address width. 0xff if no limitation.
>> + */
>> +typedef struct HostIOMMUDeviceCaps {
>> +    enum iommu_hw_info_type type;
>> +    uint8_t aw_bits;
>> +} HostIOMMUDeviceCaps;
>>
>>   #define TYPE_HOST_IOMMU_DEVICE "host-iommu-device"
>>   OBJECT_DECLARE_TYPE(HostIOMMUDevice, HostIOMMUDeviceClass,
>HOST_IOMMU_DEVICE)
>>
>>   struct HostIOMMUDevice {
>>       Object parent_obj;
>> +
>> +    HostIOMMUDeviceCaps caps;
>>   };
>>
>>   /**
>> @@ -47,5 +62,34 @@ struct HostIOMMUDeviceClass {
>>        * Returns: true on success, false on failure.
>>        */
>>       bool (*realize)(HostIOMMUDevice *hiod, void *opaque, Error **errp);
>> +    /**
>> +     * @check_cap: check if a host IOMMU device capability is supported.
>> +     *
>> +     * Optional callback, if not implemented, hint not supporting query
>> +     * of @cap.
>> +     *
>> +     * @hiod: pointer to a host IOMMU device instance.
>> +     *
>> +     * @cap: capability to check.
>> +     *
>> +     * @errp: pass an Error out when fails to query capability.
>> +     *
>> +     * Returns: <0 on failure, 0 if a @cap is unsupported, or else
>> +     * 1 or some positive value for some special @cap,
>> +     * i.e., HOST_IOMMU_DEVICE_CAP_AW_BITS.
>> +     */
>> +    int (*check_cap)(HostIOMMUDevice *hiod, int cap, Error **errp);
>>   };
>> +
>> +/*
>> + * Host IOMMU device capability list.
>> + */
>> +#define HOST_IOMMU_DEVICE_CAP_IOMMUFD       0
>> +#define HOST_IOMMU_DEVICE_CAP_IOMMU_TYPE    1
>> +#define HOST_IOMMU_DEVICE_CAP_AW_BITS       2
>> +
>> +
>> +int host_iommu_device_check_cap(HostIOMMUDevice *hiod, int cap,
>Error **errp);
>> +int host_iommu_device_check_cap_common(HostIOMMUDevice *hiod,
>int cap,
>> +                                       Error **errp);
>>   #endif
>> diff --git a/backends/host_iommu_device.c
>b/backends/host_iommu_device.c
>> index 41f2fdce20..b97d008cc7 100644
>> --- a/backends/host_iommu_device.c
>> +++ b/backends/host_iommu_device.c
>> @@ -28,3 +28,32 @@ static void host_iommu_device_init(Object *obj)
>>   static void host_iommu_device_finalize(Object *obj)
>>   {
>>   }
>> +
>> +/* Wrapper of HostIOMMUDeviceClass:check_cap */
>> +int host_iommu_device_check_cap(HostIOMMUDevice *hiod, int cap,
>Error **errp)
>
>Since we have an 'Error **errp', we could return a bool instead,
>unless this is a 'get_cap' routine ?

Maybe better to name it host_iommu_device_get_cap()?
Because not all results are bool, some are integer, i.e., aw_bits.

Thanks
Zhenzhong

>
>Thanks,
>
>C.
>
>
>> +{
>> +    HostIOMMUDeviceClass *hiodc =
>HOST_IOMMU_DEVICE_GET_CLASS(hiod);
>> +    if (!hiodc->check_cap) {
>> +        error_setg(errp, ".check_cap() not implemented");
>> +        return -EINVAL;
>> +    }
>> +
>> +    return hiodc->check_cap(hiod, cap, errp);
>> +}
>> +
>> +/* Implement check on common IOMMU capabilities */
>> +int host_iommu_device_check_cap_common(HostIOMMUDevice *hiod,
>int cap,
>> +                                       Error **errp)
>> +{
>> +    HostIOMMUDeviceCaps *caps = &hiod->caps;
>> +
>> +    switch (cap) {
>> +    case HOST_IOMMU_DEVICE_CAP_IOMMU_TYPE:
>> +        return caps->type;
>> +    case HOST_IOMMU_DEVICE_CAP_AW_BITS:
>> +        return caps->aw_bits;
>> +    default:
>> +        error_setg(errp, "Not support query cap %x", cap);
>> +        return -EINVAL;
>> +    }
>> +}