>-----Original Message-----
>From: Liu, Yi L <[email protected]>
>Subject: Re: [PATCH v5 10/21] intel_iommu: Introduce two helpers
>vtd_as_from/to_iommu_pasid_locked
>
>On 2025/9/1 13:33, Duan, Zhenzhong wrote:
>
>>>> +static int vtd_as_to_iommu_pasid_locked(VTDAddressSpace *vtd_as,
>>>> + uint32_t *pasid)
>>>> +{
>>>> + VTDContextCacheEntry *cc_entry =
>&vtd_as->context_cache_entry;
>>>> + IntelIOMMUState *s = vtd_as->iommu_state;
>>>> + uint8_t bus_num = pci_bus_num(vtd_as->bus);
>>>> + uint8_t devfn = vtd_as->devfn;
>>>> + VTDContextEntry ce;
>>>> + int ret;
>>>> +
>>>> + /* For Requests-with-PASID, its pasid value is used by vIOMMU
>>> directly */
>>>> + if (vtd_as->pasid != PCI_NO_PASID) {
>>>> + *pasid = vtd_as->pasid;
>>>> + return 0;
>>>> + }
>>>> +
>>>> + if (cc_entry->context_cache_gen == s->context_cache_gen) {
>>>> + ce = cc_entry->context_entry;
>
>just realized, if you don't record the context_entry in the below
>branch, then this flow will always go with the below branch for
>passthrough device. is it?
Yes.
>
>>>> + } else {
>>>> + ret = vtd_dev_to_context_entry(s, bus_num, devfn, &ce);
>>>> + if (ret) {
>>>> + return ret;
>>>> + }
>>>> + }
>>>> + *pasid = VTD_CE_GET_RID2PASID(&ce);
>>>
>>> looks like we have quite a few code get rid_pasid from the context
>>> entry. I think we may simplify it by using PASID #0 since vIOMMU does
>>> not report ECAP.RPS bit at all. It could be done as a separate cleanup.
>>
>> Yes, but we already have all code supporting RPS capability though RPS
>> isn't enabled in CAP register. In theory we can enable RPS easily by setting
>> the bit in CAP register. So I would like to be consistent with this instead
>> of
>> dropping all the existing code about RPS cap.
>
>right. The code is almost there. But I haven't seen the possibility to
>report RPS==1 to guest. It's somehow aligned that pasid#0 would be used
>as rid_pasid. You may have noticed Linux even does not check RPS bit. So
>such a guest will ignore RPS. This means this reading rid_pasid from ce
>entry is not necessary. This is not urgent task anyhow.
OK, if we have no plan to support RPS, a lot of code will be simplified. I'll
do it in this series if no objection.
Thanks
Zhenzhong
