Re: [PATCH v5 13/21] intel_iommu: Introduce a new pasid cache invalidation type FORCE_RESET

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

Hi Zhenzhong,

On 8/22/25 8:40 AM, Zhenzhong Duan wrote:
> FORCE_RESET is different from GLOBAL_INV which updates pasid cache if
> underlying pasid entry is still valid, it drops all the pasid caches.
>
> FORCE_RESET isn't a VTD spec defined invalidation type for pasid cache,
> only used internally in system level reset.
>
> Signed-off-by: Yi Liu <yi.l.liu@intel.com>
> Signed-off-by: Yi Sun <yi.y.sun@linux.intel.com>
> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
> ---
>  hw/i386/intel_iommu_internal.h |  9 +++++++++
>  hw/i386/intel_iommu.c          | 25 +++++++++++++++++++++++++
>  hw/i386/trace-events           |  1 +
>  3 files changed, 35 insertions(+)
>
> diff --git a/hw/i386/intel_iommu_internal.h b/hw/i386/intel_iommu_internal.h
> index fb2a919e87..c510b09d1a 100644
> --- a/hw/i386/intel_iommu_internal.h
> +++ b/hw/i386/intel_iommu_internal.h
> @@ -569,6 +569,15 @@ typedef enum VTDPCInvType {
>      VTD_PASID_CACHE_DOMSI = VTD_INV_DESC_PASIDC_G_DSI,
>      VTD_PASID_CACHE_PASIDSI = VTD_INV_DESC_PASIDC_G_PASID_SI,
>      VTD_PASID_CACHE_GLOBAL_INV = VTD_INV_DESC_PASIDC_G_GLOBAL,
> +
> +    /*
> +     * Internally used PASID cache invalidation type starts here,
> +     * 0x10 is large enough as invalidation type in pc_inv_desc
> +     * is 2bits in size.
> +     */
> +
> +    /* Reset all PASID cache entries, used in system level reset */
> +    VTD_PASID_CACHE_FORCE_RESET = 0x10,
I am not very keen on adding such an artifical enum value that does not
exist in the spec.

Why not simply introduce another function (instead of
vtd_flush_pasid_locked) that does the cleanup. To me it would be
cleaner. Thanks Eric
>  } VTDPCInvType;
>  
>  typedef struct VTDPASIDCacheInfo {
> diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
> index 7d2c9feae7..af384ce7f0 100644
> --- a/hw/i386/intel_iommu.c
> +++ b/hw/i386/intel_iommu.c
> @@ -87,6 +87,8 @@ struct vtd_iotlb_key {
>  static void vtd_address_space_refresh_all(IntelIOMMUState *s);
>  static void vtd_address_space_unmap(VTDAddressSpace *as, IOMMUNotifier *n);
>  
> +static void vtd_pasid_cache_reset_locked(IntelIOMMUState *s);
> +
>  static void vtd_panic_require_caching_mode(void)
>  {
>      error_report("We need to set caching-mode=on for intel-iommu to enable "
> @@ -391,6 +393,7 @@ static void vtd_reset_caches(IntelIOMMUState *s)
>      vtd_iommu_lock(s);
>      vtd_reset_iotlb_locked(s);
>      vtd_reset_context_cache_locked(s);
> +    vtd_pasid_cache_reset_locked(s);
>      vtd_iommu_unlock(s);
>  }
>  
> @@ -3183,6 +3186,8 @@ static gboolean vtd_flush_pasid_locked(gpointer key, gpointer value,
>          /* fall through */
>      case VTD_PASID_CACHE_GLOBAL_INV:
>          break;
> +    case VTD_PASID_CACHE_FORCE_RESET:
> +        goto remove;
>      default:
>          error_setg(&error_fatal, "invalid pc_info->type for flush");
>      }
> @@ -3225,6 +3230,23 @@ remove:
>      return true;
>  }
>  
> +static void vtd_pasid_cache_reset_locked(IntelIOMMUState *s)
> +{
> +    VTDPASIDCacheInfo pc_info;
> +
> +    trace_vtd_pasid_cache_reset();
> +
> +    pc_info.type = VTD_PASID_CACHE_FORCE_RESET;
> +
> +    /*
> +     * Reset pasid cache is a big hammer, so use g_hash_table_foreach_remove
> +     * which will free all vtd_as instances except those created for PCI
> +     * sub-system.
> +     */
> +    g_hash_table_foreach_remove(s->vtd_address_spaces,
> +                                vtd_flush_pasid_locked, &pc_info);
> +}
> +
>  /*
>   * This function walks over PASID range within [start, end) in a single
>   * PASID table for entries matching @info type/did, then retrieve/create
> @@ -3363,6 +3385,9 @@ static void vtd_replay_guest_pasid_bindings(IntelIOMMUState *s,
>      case VTD_PASID_CACHE_GLOBAL_INV:
>          /* loop all assigned devices */
>          break;
> +    case VTD_PASID_CACHE_FORCE_RESET:
> +        /* For force reset, no need to go further replay */
> +        return;
>      default:
>          error_setg(&error_fatal, "invalid pc_info->type for replay");
>      }
> diff --git a/hw/i386/trace-events b/hw/i386/trace-events
> index ae5bbfcdc0..c8a936eb46 100644
> --- a/hw/i386/trace-events
> +++ b/hw/i386/trace-events
> @@ -24,6 +24,7 @@ vtd_inv_qi_head(uint16_t head) "read head %d"
>  vtd_inv_qi_tail(uint16_t head) "write tail %d"
>  vtd_inv_qi_fetch(void) ""
>  vtd_context_cache_reset(void) ""
> +vtd_pasid_cache_reset(void) ""
>  vtd_pasid_cache_gsi(void) ""
>  vtd_pasid_cache_dsi(uint16_t domain) "Domain selective PC invalidation domain 0x%"PRIx16
>  vtd_pasid_cache_psi(uint16_t domain, uint32_t pasid) "PASID selective PC invalidation domain 0x%"PRIx16" pasid 0x%"PRIx32