Re: [PATCH v1 05/15] intel_iommu: Introduce two helpers vtd_as_from/to_iommu_pasid_locked

[Yi Liu <yi.l.liu@intel.com>]

On 2025/6/6 18:04, Zhenzhong Duan wrote:
> We already have vtd_find_add_as() to find an AS from BDF+pasid, but this
> pasid is passed from PCI subsystem. 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.

When reading the first line, it makes me thinking why need the helpers
since there is already a helper to find. The key is the later part. We need
to translate the PCI_NO_PASID to ridpasid.

> 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 | 50 +++++++++++++++++++++++++++++++++++++++++++
>   1 file changed, 50 insertions(+)
> 
> diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
> index 796b71605c..112e09e305 100644
> --- a/hw/i386/intel_iommu.c
> +++ b/hw/i386/intel_iommu.c
> @@ -1617,6 +1617,56 @@ static int vtd_as_to_context_entry(VTDAddressSpace *vtd_as, VTDContextEntry *ce)
>       }
>   }
>   
> +static inline int vtd_as_to_iommu_pasid_locked(VTDAddressSpace *vtd_as,
> +                                               uint32_t *pasid)
> +{
> +    VTDContextEntry ce;
> +    int ret;
> +
> +    ret = vtd_as_to_context_entry(vtd_as, &ce);
> +    if (ret) {
> +        return ret;
> +    }
> +
> +    /* 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;
> +    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 */
> +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)
>   {

-- 
Regards,
Yi Liu