Re: [PATCH v2 09/19] intel_iommu: Introduce two helpers vtd_as_from/to_iommu_pasid_locked

[Eric Auger <eric.auger@redhat.com>]

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.duan@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.

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.
> +{
> +    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.
> +
> +    /* 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?
> +    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