Hi Eric,
>-----Original Message-----
>From: Duan, Zhenzhong
>Subject: RE: [PATCH v2 09/19] intel_iommu: Introduce two helpers
>vtd_as_from/to_iommu_pasid_locked
>
>
>
>>-----Original Message-----
>>From: Eric Auger <eric.au...@redhat.com>
>>Subject: Re: [PATCH v2 09/19] intel_iommu: Introduce two helpers
>>vtd_as_from/to_iommu_pasid_locked
>>
>>Hi Zhenzhong,
>>
>>On 6/20/25 9:18 AM, Zhenzhong Duan wrote:
>>> PCI device supports two request types, Requests-without-PASID and
>>> Requests-with-PASID. Requests-without-PASID doesn't include a PASID TLP
>>> prefix, IOMMU fetches rid_pasid from context entry and use it as
>IOMMU's
>>> pasid to index pasid table.
>>>
>>> So we need to translate between PCI's pasid and IOMMU's pasid specially
>>> for Requests-without-PASID, e.g., PCI_NO_PASID(-1) <-> rid_pasid.
>>> For Requests-with-PASID, PCI's pasid and IOMMU's pasid are same value.
>>>
>>> vtd_as_from_iommu_pasid_locked() translates from BDF+iommu_pasid to
>>vtd_as
>>> which contains PCI's pasid vtd_as->pasid.
>>>
>>> vtd_as_to_iommu_pasid_locked() translates from BDF+vtd_as->pasid to
>>iommu_pasid.
>>>
>>> Signed-off-by: Zhenzhong Duan <zhenzhong.d...@intel.com>
>>> ---
>>> hw/i386/intel_iommu.c | 58
>>+++++++++++++++++++++++++++++++++++++++++++
>>> 1 file changed, 58 insertions(+)
>>>
>>> diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
>>> index 9d4adc9458..8948b8370f 100644
>>> --- a/hw/i386/intel_iommu.c
>>> +++ b/hw/i386/intel_iommu.c
>>> @@ -1602,6 +1602,64 @@ static int
>>vtd_dev_to_context_entry(IntelIOMMUState *s, uint8_t bus_num,
>>> return 0;
>>> }
>>>
>>> +static inline int vtd_as_to_iommu_pasid_locked(VTDAddressSpace
>*vtd_as,
>>> + uint32_t
>*pasid)
>>Is it meaningful to use inline here and below? Below I guess you do so
>>to avoid "defined but not used" compilation error but I don't think it
>>should stay as is.
>
>Yes, that's the only reason I define the both inline.
>Do you have other suggestions to avoid compilation error if not use inline?
I find I am not clear on above comments yet, do you just want to remove inline
flag?
Maybe merging the two helpers to other patches using them to avoid inline?
If I misunderstood, could you share more light on what changes you want this
piece of code to have?
Thanks
Zhenzhong
>
>>
>>I don't really understand the iommu_pasid terminology. Either it is a
>>pasid passed through the PCI transaction or it is the default pasid
>>found in rid2passid ce field. So that's a pasid both ways ;-) can't you
>>simply call it pasid.
>
>Yes, PCI side we call it just pasid, the other side I name it iommu pasid to
>distinguish.
>Does that work for you?
>
>>> +{
>>> + 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;
>>> +
>>> + if (cc_entry->context_cache_gen == s->context_cache_gen) {
>>> + ce = cc_entry->context_entry;
>>> + } else {
>>> + ret = vtd_dev_to_context_entry(s, bus_num, devfn, &ce);
>>> + if (ret) {
>>> + return ret;
>>> + }
>>> + }
>>if the above pattern is used at many locations I still think it may be
>>valuable to have a _locked helper.
>
>Not get, both vtd_as_to_iommu_pasid_locked() and
>vtd_as_from_iommu_pasid_locked()
>are already _locked helper, isn't it?
>
>Do you mean adding a comment saying "Caller of this function should hold
>iommu_lock."
>
>>> +
>>> + /* Translate to iommu pasid if PCI_NO_PASID */
>>> + if (vtd_as->pasid == PCI_NO_PASID) {
>>> + *pasid = VTD_CE_GET_RID2PASID(&ce);
>>> + } else {
>>> + *pasid = vtd_as->pasid;
>>> + }
>>> +
>>> + return 0;
>>> +}
>>> +
>>> +static gboolean vtd_find_as_by_sid_and_iommu_pasid(gpointer key,
>gpointer
>>value,
>>> + gpointer
>user_data)
>>> +{
>>> + VTDAddressSpace *vtd_as = (VTDAddressSpace *)value;
>>> + struct vtd_as_raw_key *target = (struct vtd_as_raw_key
>*)user_data;
>>why target? can't you name it key instead?
>
>There is already a parameter named key, maybe target_key?
>
>Thanks
>Zhenzhong
>
>>> + uint16_t sid = PCI_BUILD_BDF(pci_bus_num(vtd_as->bus),
>vtd_as->devfn);
>>> + uint32_t pasid;
>>> +
>>> + if (vtd_as_to_iommu_pasid_locked(vtd_as, &pasid)) {
>>> + return false;
>>> + }
>>> +
>>> + return (pasid == target->pasid) && (sid == target->sid);
>>> +}
>>> +
>>> +/* Translate iommu pasid to vtd_as */
>>same here
>>> +static inline
>>> +VTDAddressSpace *vtd_as_from_iommu_pasid_locked(IntelIOMMUState
>*s,
>>> + uint16_t sid,
>uint32_t pasid)
>>> +{
>>> + struct vtd_as_raw_key key = {
>>> + .sid = sid,
>>> + .pasid = pasid
>>> + };
>>> +
>>> + return g_hash_table_find(s->vtd_address_spaces,
>>> +
>vtd_find_as_by_sid_and_iommu_pasid, &key);
>>> +}
>>> +
>>> static int vtd_sync_shadow_page_hook(const IOMMUTLBEvent *event,
>>> void *private)
>>> {
>>Thanks
>>
>>Eric
