Re: [PATCH 2/2] xen/dm: arm: Introduce inject_msi2 DM op

[Mykyta Poturai <Mykyta_Poturai@xxxxxxxx>]

On 20.03.25 15:07, Oleksandr Tyshchenko wrote:
>>> If I got correctly what is wrote in current thread (and in RFC version
>>> where it was an attempt to create just Arm64's counterpart of
>>> XEN_DMOP_inject_msi), my understanding (maybe not precise/correct, since
>>> I am not quite familiar with x86 details) that we would need something
>>> like that:
>>>
>>>
>>> /*
>>>    * XEN_DMOP_inject_msi2: An enhanced version of the sub-ob to 
>>> inject an MSI
>>>    *                       for an emulated device, which allows 
>>> specifying
>>>    *                       the ID of the device triggering the MSI
>>> (source ID).
>>>    *
>>>    * The source ID is specified by a pair of <segment> and <source_id>.
>>>    * If <flags> does not contain XEN_DMOP_MSI_SOURCE_ID_VALID then 
>>> source ID
>>>    * is invalid and should be ignored.
>>>    */
>>> #define XEN_DMOP_inject_msi 21
>>>
>>> struct xen_dm_op_inject_msi2 {
>>>        /* IN - MSI data */
>>>        uint32_t data;
>>>        /* IN - next two fields form an ID of the device triggering 
>>> the MSI */
>>>        uint16_t segment; /* The segment number */
>>>        uint16_t source_id; /* The source ID that is local to segment 
>>> (PCI
>>> BDF) */
>>>        /* IN - types of source ID */
>>>        uint32_t flags;
>>> #define XEN_DMOP_MSI_SOURCE_ID_VALID (1u << 0)
>>>        uint32_t pad;
>>>        /* IN - MSI address */
>>>        uint64_aligned_t addr;
>>> };
>>>
>>>
>>> This is arch agnostic sub-op without the (obvious) specifics of the
>>> underlying MSI controller. The sub-ob, I hope, will be suitable on both
>>> Arm64 soon (segment + source_id provide vSBDF, then it will possible to
>>> locate vITS and devid) and on x86 in future (for the vIOMMU needs).
>>>
>>> Would you be ok with that in general? Please share you opinion.
>>
>> Yes, this looks plausible.
> 
> Jan, thanks
> 
> 
>   In the context of things like VMD (using
>> software established segment numbers wider than 16 bits) I wonder
>> though whether we wouldn't better make segment and source ID 32-bit
>> fields from the beginning.
> 
> Keeping in mind that dm_op hypercall is stable and segment can be >= 
> 0x10000, probably yes, makes sense to use 32-bit from the very beginning.
> 
> 
>   Out-of-range values would of course need
>> rejecting then.
> 
> yes, sure
> 
> ***
> 
> Mykyta, are you ok with the proposed adjustments to the sub-op structure?
> 
>>
>> Jan

Yes, seems fine for me. I will use it in the next version.

-- 
Mykyta