RE: [RFC v3 16/25] intel_iommu: add PASID cache management infrastructure

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

> From: Peter Xu <peterx@redhat.com>
> Sent: Wednesday, February 12, 2020 7:36 AM
> To: Liu, Yi L <yi.l.liu@intel.com>
> Subject: Re: [RFC v3 16/25] intel_iommu: add PASID cache management
> infrastructure
> 
> On Wed, Jan 29, 2020 at 04:16:47AM -0800, Liu, Yi L wrote:
> > From: Liu Yi L <yi.l.liu@intel.com>
> >
> > This patch adds a PASID cache management infrastructure based on
> > new added structure VTDPASIDAddressSpace, which is used to track
> > the PASID usage and future PASID tagged DMA address translation
> > support in vIOMMU.
> >
> >     struct VTDPASIDAddressSpace {
> >         VTDBus *vtd_bus;
> >         uint8_t devfn;
> >         AddressSpace as;
> >         uint32_t pasid;
> >         IntelIOMMUState *iommu_state;
> >         VTDContextCacheEntry context_cache_entry;
> >         QLIST_ENTRY(VTDPASIDAddressSpace) next;
> >         VTDPASIDCacheEntry pasid_cache_entry;
> >     };
> >
> > Ideally, a VTDPASIDAddressSpace instance is created when a PASID
> > is bound with a DMA AddressSpace. Intel VT-d spec requires guest
> > software to issue pasid cache invalidation when bind or unbind a
> > pasid with an address space under caching-mode. However, as
> > VTDPASIDAddressSpace instances also act as pasid cache in this
> > implementation, its creation also happens during vIOMMU PASID
> > tagged DMA translation. The creation in this path will not be
> > added in this patch since no PASID-capable emulated devices for
> > now.
> >
> > The implementation in this patch manages VTDPASIDAddressSpace
> > instances per PASID+BDF (lookup and insert will use PASID and
> > BDF) since Intel VT-d spec allows per-BDF PASID Table. When a
> > guest bind a PASID with an AddressSpace, QEMU will capture the
> > guest pasid selective pasid cache invalidation, and allocate
> > remove a VTDPASIDAddressSpace instance per the invalidation
> > reasons:
> >
> >     *) a present pasid entry moved to non-present
> >     *) a present pasid entry to be a present entry
> >     *) a non-present pasid entry moved to present
> >
> > vIOMMU emulator could figure out the reason by fetching latest
> > guest pasid entry.
> >
> > Cc: Kevin Tian <kevin.tian@intel.com>
> > Cc: Jacob Pan <jacob.jun.pan@linux.intel.com>
> > Cc: Peter Xu <peterx@redhat.com>
> > Cc: Yi Sun <yi.y.sun@linux.intel.com>
> > Cc: Paolo Bonzini <pbonzini@redhat.com>
> > Cc: Richard Henderson <rth@twiddle.net>
> > Cc: Eduardo Habkost <ehabkost@redhat.com>
> > Signed-off-by: Liu Yi L <yi.l.liu@intel.com>
> > ---
> >  hw/i386/intel_iommu.c          | 367
> +++++++++++++++++++++++++++++++++++++++++
> >  hw/i386/intel_iommu_internal.h |  14 ++
> >  hw/i386/trace-events           |   1 +
> >  include/hw/i386/intel_iommu.h  |  36 +++-
> >  4 files changed, 417 insertions(+), 1 deletion(-)
> >
> > diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
> > index 58e7213..c75cb7b 100644
> > --- a/hw/i386/intel_iommu.c
> > +++ b/hw/i386/intel_iommu.c
> > @@ -40,6 +40,7 @@
> >  #include "kvm_i386.h"
> >  #include "migration/vmstate.h"
> >  #include "trace.h"
> > +#include "qemu/jhash.h"
> >
> >  /* context entry operations */
> >  #define VTD_CE_GET_RID2PASID(ce) \
> > @@ -65,6 +66,8 @@
> >  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(IntelIOMMUState *s);
> > +
> >  static void vtd_panic_require_caching_mode(void)
> >  {
> >      error_report("We need to set caching-mode=on for intel-iommu to enable "
> > @@ -276,6 +279,7 @@ 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(s);
> >      vtd_iommu_unlock(s);
> >  }
> >
> > @@ -686,6 +690,11 @@ static inline bool vtd_pe_type_check(X86IOMMUState
> *x86_iommu,
> >      return true;
> >  }
> >
> > +static inline uint16_t vtd_pe_get_domain_id(VTDPASIDEntry *pe)
> > +{
> > +    return VTD_SM_PASID_ENTRY_DID((pe)->val[1]);
> > +}
> > +
> >  static inline bool vtd_pdire_present(VTDPASIDDirEntry *pdire)
> >  {
> >      return pdire->val & 1;
> > @@ -2393,19 +2402,370 @@ static bool
> vtd_process_iotlb_desc(IntelIOMMUState *s, VTDInvDesc *inv_desc)
> >      return true;
> >  }
> >
> > +static inline void vtd_init_pasid_key(uint32_t pasid,
> > +                                     uint16_t sid,
> > +                                     struct pasid_key *key)
> > +{
> > +    key->pasid = pasid;
> > +    key->sid = sid;
> > +}
> > +
> > +static guint vtd_pasid_as_key_hash(gconstpointer v)
> > +{
> > +    struct pasid_key *key = (struct pasid_key *)v;
> > +    uint32_t a, b, c;
> > +
> > +    /* Jenkins hash */
> > +    a = b = c = JHASH_INITVAL + sizeof(*key);
> > +    a += key->sid;
> > +    b += extract32(key->pasid, 0, 16);
> > +    c += extract32(key->pasid, 16, 16);
> > +
> > +    __jhash_mix(a, b, c);
> > +    __jhash_final(a, b, c);
> > +
> > +    return c;
> > +}
> > +
> > +static gboolean vtd_pasid_as_key_equal(gconstpointer v1, gconstpointer v2)
> > +{
> > +    const struct pasid_key *k1 = v1;
> > +    const struct pasid_key *k2 = v2;
> > +
> > +    return (k1->pasid == k2->pasid) && (k1->sid == k2->sid);
> > +}
> > +
> > +static inline int vtd_dev_get_pe_from_pasid(IntelIOMMUState *s,
> > +                                            uint8_t bus_num,
> > +                                            uint8_t devfn,
> > +                                            uint32_t pasid,
> > +                                            VTDPASIDEntry *pe)
> > +{
> > +    VTDContextEntry ce;
> > +    int ret;
> > +    dma_addr_t pasid_dir_base;
> > +
> > +    if (!s->root_scalable) {
> > +        return -VTD_FR_PASID_TABLE_INV;
> > +    }
> > +
> > +    ret = vtd_dev_to_context_entry(s, bus_num, devfn, &ce);
> > +    if (ret) {
> > +        return ret;
> > +    }
> > +
> > +    pasid_dir_base = VTD_CE_GET_PASID_DIR_TABLE(&ce);
> > +    ret = vtd_get_pe_from_pasid_table(s,
> > +                                  pasid_dir_base, pasid, pe);
> > +
> > +    return ret;
> > +}
> > +
> > +static bool vtd_pasid_entry_compare(VTDPASIDEntry *p1, VTDPASIDEntry
> *p2)
> > +{
> > +    return !memcmp(p1, p2, sizeof(*p1));
> > +}
> > +
> > +/**
> > + * This function is used to clear pasid_cache_gen of cached pasid
> > + * entry in vtd_pasid_as instances. Caller of this function should
> > + * hold iommu_lock.
> > + */
> > +static gboolean vtd_flush_pasid(gpointer key, gpointer value,
> > +                                gpointer user_data)
> > +{
> > +    VTDPASIDCacheInfo *pc_info = user_data;
> > +    VTDPASIDAddressSpace *vtd_pasid_as = value;
> > +    IntelIOMMUState *s = vtd_pasid_as->iommu_state;
> > +    VTDPASIDCacheEntry *pc_entry = &vtd_pasid_as->pasid_cache_entry;
> > +    VTDBus *vtd_bus = vtd_pasid_as->vtd_bus;
> > +    VTDPASIDEntry pe;
> > +    uint16_t did;
> > +    uint32_t pasid;
> > +    uint16_t devfn;
> > +    int ret;
> > +
> > +    did = vtd_pe_get_domain_id(&pc_entry->pasid_entry);
> > +    pasid = vtd_pasid_as->pasid;
> > +    devfn = vtd_pasid_as->devfn;
> > +
> > +    if (!(pc_entry->pasid_cache_gen == s->pasid_cache_gen)) {
> > +        return false;
> > +    }
> > +
> > +    switch (pc_info->flags & VTD_PASID_CACHE_INFO_MASK) {
> > +    case VTD_PASID_CACHE_PASIDSI:
> > +        if (pc_info->pasid != pasid) {
> > +            return false;
> > +        }
> > +        /* Fall through */
> 
> Why fall through?

For VTD_PASID_CACHE_PASIDSI, it implies domain selective, so it
requires to check did just as VTD_PASID_CACHE_DOMSI.

> 
> > +    case VTD_PASID_CACHE_DOMSI:
> > +        if (pc_info->domain_id != did) {
> > +            return false;
> > +        }
> > +        /* Fall through */
> 
> Same here.

If code comes to here, it means the necessary checks are passed. Should
add a break here. However, as the below case does nothing and just calls
break. So I let the code fall through.

> 
> > +    case VTD_PASID_CACHE_GLOBAL:
> > +        break;
> > +    default:
> 
> Nevee reach here right?  If so we can abort.

yes, should never reach here.

> > +        return false;
> > +    }
> > +
> > +    /*
> > +     * pasid cache invalidation may indicate a present pasid
> > +     * entry to present pasid entry modification. To cover such
> > +     * case, vIOMMU emulator needs to fetch latest guest pasid
> > +     * entry and check cached pasid entry, then update pasid
> > +     * cache and send pasid bind/unbind to host properly.
> > +     */
> > +    ret = vtd_dev_get_pe_from_pasid(s,
> > +                  pci_bus_num(vtd_bus->bus), devfn, pasid, &pe);
> > +    if (ret) {
> > +        /*
> > +         * No valid pasid entry in guest memory. e.g. pasid entry
> > +         * was modified to be either all-zero or non-present. Either
> > +         * case means existing pasid cache should be removed.
> > +         */
> > +        goto remove;
> > +    }
> > +    /* Compare cached pasid entry and latest pasid entry */
> > +    if (!vtd_pasid_entry_compare(&pe, &pc_entry->pasid_entry)) {
> > +        /* pasid entry was updated, thus update the pasid cache */
> > +        pc_entry->pasid_entry = pe;
> > +        pc_entry->pasid_cache_gen = s->pasid_cache_gen;
> > +        /*
> > +         * TODO:
> > +         * - send pasid bind to host for passthru devices
> > +         * - when pasid-base-iotlb(piotlb) infrastructure is ready,
> > +         *   should invalidate QEMU piotlb togehter with this change.
> > +         */
> > +    }
> > +    return false;
> > +remove:
> > +    /*
> > +     * TODO:
> > +     * - send pasid unbind to host for passthru devices
> > +     * - when pasid-base-iotlb(piotlb) infrastructure is ready,
> > +     *   should invalidate QEMU piotlb togehter with this change.
> > +     */
> > +    return true;
> > +}
> > +
> >  static int vtd_pasid_cache_dsi(IntelIOMMUState *s, uint16_t domain_id)
> >  {
> > +    VTDPASIDCacheInfo pc_info;
> > +
> > +    trace_vtd_pasid_cache_dsi(domain_id);
> > +
> > +    pc_info.flags = VTD_PASID_CACHE_DOMSI;
> > +    pc_info.domain_id = domain_id;
> > +
> > +    /*
> > +     * Loop all existing pasid caches and update them.
> > +     */
> > +    vtd_iommu_lock(s);
> > +    g_hash_table_foreach_remove(s->vtd_pasid_as,
> > +                                 vtd_flush_pasid, &pc_info);
> > +
> > +    /*
> > +     * TODO: Domain selective PASID cache invalidation
> > +     * flushes all the pasid caches within a domain. To
> > +     * be safe, after invalidating the pasid caches, emulator
> > +     * needs to replay the pasid bindings by walking guest
> > +     * pasid dir and pasid table.
> 
> Better spell out on what special case we're handling here: When the
> guest setup a new PASID entry then send a PASID DSI.

oh, yes.  will add it in new version. :-)

> 
> > +     */
> > +    vtd_iommu_unlock(s);
> >      return 0;
> >  }
> >
> > +/**
> > + * This function finds or adds a VTDPASIDAddressSpace for a device
> > + * when it is bound to a pasid. Caller of this function should hold
> > + * iommu_lock.
> > + */
> > +static VTDPASIDAddressSpace *vtd_add_find_pasid_as(IntelIOMMUState *s,
> > +                                                   VTDBus *vtd_bus,
> > +                                                   int devfn,
> > +                                                   uint32_t pasid,
> > +                                                   bool allocate)
> > +{
> > +    struct pasid_key key;
> > +    struct pasid_key *new_key;
> > +    VTDPASIDAddressSpace *vtd_pasid_as;
> > +    uint16_t sid;
> > +
> > +    sid = vtd_make_source_id(pci_bus_num(vtd_bus->bus), devfn);
> > +    vtd_init_pasid_key(pasid, sid, &key);
> > +    vtd_pasid_as = g_hash_table_lookup(s->vtd_pasid_as, &key);
> > +
> > +    if (!vtd_pasid_as && allocate) {
> > +        new_key = g_malloc0(sizeof(*new_key));
> > +        vtd_init_pasid_key(pasid, sid, new_key);
> > +        /*
> > +         * Initiate the vtd_pasid_as structure.
> > +         *
> > +         * This structure here is used to track the guest pasid
> > +         * binding and also serves as pasid-cache mangement entry.
> > +         *
> > +         * TODO: in future, if wants to support the SVA-aware DMA
> > +         *       emulation, the vtd_pasid_as should have include
> > +         *       AddressSpace to support DMA emulation.
> > +         */
> > +        vtd_pasid_as = g_malloc0(sizeof(VTDPASIDAddressSpace));
> > +        vtd_pasid_as->iommu_state = s;
> > +        vtd_pasid_as->vtd_bus = vtd_bus;
> > +        vtd_pasid_as->devfn = devfn;
> > +        vtd_pasid_as->context_cache_entry.context_cache_gen = 0;
> > +        vtd_pasid_as->pasid = pasid;
> > +        vtd_pasid_as->pasid_cache_entry.pasid_cache_gen = 0;
> > +        g_hash_table_insert(s->vtd_pasid_as, new_key, vtd_pasid_as);
> > +    }
> > +    return vtd_pasid_as;
> > +}
> > +
> > + /**
> > +  * This function updates the pasid entry cached in &vtd_pasid_as.
> > +  * Caller of this function should hold iommu_lock.
> > +  */
> > +static inline void vtd_fill_in_pe_cache(
> > +              VTDPASIDAddressSpace *vtd_pasid_as, VTDPASIDEntry *pe)
> > +{
> > +    IntelIOMMUState *s = vtd_pasid_as->iommu_state;
> > +    VTDPASIDCacheEntry *pc_entry = &vtd_pasid_as->pasid_cache_entry;
> > +
> > +    pc_entry->pasid_entry = *pe;
> > +    pc_entry->pasid_cache_gen = s->pasid_cache_gen;
> > +}
> > +
> >  static int vtd_pasid_cache_psi(IntelIOMMUState *s,
> >                                 uint16_t domain_id, uint32_t pasid)
> >  {
> > +    VTDPASIDCacheInfo pc_info;
> > +    VTDPASIDEntry pe;
> > +    VTDBus *vtd_bus;
> > +    int bus_n, devfn;
> > +    VTDPASIDAddressSpace *vtd_pasid_as;
> > +    VTDIOMMUContext *vtd_icx;
> > +
> > +    /* PASID selective implies a DID selective */
> > +    pc_info.flags = VTD_PASID_CACHE_PASIDSI;
> > +    pc_info.domain_id = domain_id;
> > +    pc_info.pasid = pasid;
> > +
> > +    /*
> > +     * Regards to a pasid selective pasid cache invalidation (PSI),
> > +     * it could be either cases of below:
> > +     * a) a present pasid entry moved to non-present
> > +     * b) a present pasid entry to be a present entry
> > +     * c) a non-present pasid entry moved to present
> > +     *
> > +     * Here the handling of a PSI is:
> > +     * 1) loop all the exisitng vtd_pasid_as instances to update them
> > +     *    according to the latest guest pasid entry in pasid table.
> > +     *    this will make sure affected existing vtd_pasid_as instances
> > +     *    cached the latest pasid entries. Also, during the loop, the
> > +     *    host should be notified if needed. e.g. pasid unbind or pasid
> > +     *    update. Should be able to cover case a) and case b).
> > +     *
> > +     * 2) loop all devices to cover case c)
> > +     *    However, it is not good to always loop all devices. In this
> > +     *    implementation. We do it in this ways:
> > +     *    - For devices which have VTDIOMMUContext instances,
> > +     *      we loop them and check if guest pasid entry exists. If yes,
> > +     *      it is case c), we update the pasid cache and also notify
> > +     *      host.
> > +     *    - For devices which have no VTDIOMMUContext
> > +     *      instances, it is not necessary to create pasid cache at
> > +     *      this phase since it could be created when vIOMMU do DMA
> > +     *      address translation. This is not implemented yet since
> > +     *      no PASID-capable emulated devices today. If we have it
> > +     *      in future, the pasid cache shall be created there.
> > +     */
> > +
> > +    vtd_iommu_lock(s);
> > +    g_hash_table_foreach_remove(s->vtd_pasid_as,
> > +                                vtd_flush_pasid, &pc_info);
> > +
> > +    QLIST_FOREACH(vtd_icx, &s->vtd_dev_icx_list, next) {
> > +        vtd_bus = vtd_icx->vtd_bus;
> > +        devfn = vtd_icx->devfn;
> > +        bus_n = pci_bus_num(vtd_bus->bus);
> > +
> > +        /* Step 1: fetch vtd_pasid_as and check if it is valid */
> > +        vtd_pasid_as = vtd_add_find_pasid_as(s, vtd_bus,
> > +                                        devfn, pasid, true);
> 
> I feel like you wanted to pass "false" here for "allocate".

emmm, yeah. It was "false" in draft code as step 1 is only to check if
a valid vtd_pasid_as exists. And in step 3, it needs to call
vtd_add_find_pasid_as() with "allocate" be "true". In vtd_add_find_pasid_as(),
it will try search vtd_pasid_as first and then allocate a new one. In such
logic, there will be two vtd_add_find_pasid_as() callig and means two hash
table searching.

So I mofified it to be "true" to save a vtd_add_find_pasid_as() calling. If
a vtd_pasid_as is valid, its pasid_cache_gen will be equal to s->pasid_cache_gen.
If not, the vtd_pasid_as is a newly allocated and needs to go through step 2
and step 3 to fulfill it. Looks like I missed to free the vtd_pasid_as when step
2 failed. Will add it if you are fine with the current logic.


> > +        if (vtd_pasid_as &&
> > +            (s->pasid_cache_gen ==
> > +             vtd_pasid_as->pasid_cache_entry.pasid_cache_gen)) {
> > +            /*
> > +             * pasid_cache_gen equals to s->pasid_cache_gen means
> > +             * vtd_pasid_as is valid after the above s->vtd_pasid_as
> > +             * updates. Thus no need for the below steps.
> > +             */
> > +            continue;
> > +        }
> > +
> > +        /*
> > +         * Step 2: vtd_pasid_as is not valid, it's potentailly a
> > +         * new pasid bind. Fetch guest pasid entry.
> > +         */
> > +        if (vtd_dev_get_pe_from_pasid(s, bus_n, devfn, pasid, &pe)) {
> > +            continue;
> > +        }
> > +
> > +        /*
> > +         * Step 3: pasid entry exists, update pasid cache
> > +         *
> > +         * Here need to check domain ID since guest pasid entry
> > +         * exists. What needs to do are:
> > +         *   - update the pc_entry in the vtd_pasid_as
> > +         *   - set proper pc_entry.pasid_cache_gen
> > +         *   - pass down the latest guest pasid entry config to host
> > +         *     (will be added in later patch)
> > +         */
> > +        if (domain_id == vtd_pe_get_domain_id(&pe)) {
> > +            vtd_fill_in_pe_cache(vtd_pasid_as, &pe);
> > +        }
> > +    }
> > +    vtd_iommu_unlock(s);
> >      return 0;
> >  }
> >
> > +/**
> > + * Caller of this function should hold iommu_lock
> > + */
> > +static void vtd_pasid_cache_reset(IntelIOMMUState *s)
> > +{
> > +    VTDPASIDCacheInfo pc_info;
> > +
> > +    trace_vtd_pasid_cache_reset();
> > +
> > +    pc_info.flags = VTD_PASID_CACHE_GLOBAL;
> > +
> > +    /*
> > +     * Reset pasid cache is a big hammer, so use
> > +     * g_hash_table_foreach_remove which will free
> > +     * the vtd_pasid_as instances.
> > +     */
> > +    g_hash_table_foreach_remove(s->vtd_pasid_as,
> > +                           vtd_flush_pasid, &pc_info);
> > +    s->pasid_cache_gen = 1;
> > +}
> > +
> >  static int vtd_pasid_cache_gsi(IntelIOMMUState *s)
> >  {
> > +    trace_vtd_pasid_cache_gsi();
> > +
> > +    vtd_iommu_lock(s);
> > +    vtd_pasid_cache_reset(s);
> 
> [1]
> 
> > +
> > +    /*
> > +     * TODO: Global PASID cache invalidation may be
> > +     * flushes all the pasid caches. To be safe, after
> > +     * invalidating the pasid caches, emulator needs
> > +     * to replay the pasid bindings by walking guest
> > +     * pasid dir and pasid table.
> > +     */
> > +    vtd_iommu_unlock(s);
> >      return 0;
> >  }
> >
> > @@ -3659,8 +4019,11 @@ static int
> vtd_icx_register_ds_iommu(IOMMUContext *iommu_ctx,
> >      VTDIOMMUContext *vtd_dev_icx = container_of(iommu_ctx,
> >                                                 VTDIOMMUContext,
> >                                                 iommu_context);
> > +    IntelIOMMUState *s = vtd_dev_icx->iommu_state;
> >
> >      vtd_dev_icx->dsi_obj = dsi_obj;
> > +    QLIST_INSERT_HEAD(&s->vtd_dev_icx_list, vtd_dev_icx, next);
> > +
> >      return 0;
> >  }
> >
> > @@ -3672,6 +4035,7 @@ static void
> vtd_icx_unregister_ds_iommu(IOMMUContext *iommu_ctx,
> >                                                 iommu_context);
> >
> >      vtd_dev_icx->dsi_obj = NULL;
> > +    QLIST_REMOVE(vtd_dev_icx, next);
> >  }
> >
> >  IOMMUContextOps vtd_iommu_context_ops = {
> > @@ -4130,6 +4494,7 @@ static void vtd_realize(DeviceState *dev, Error **errp)
> >      }
> >
> >      QLIST_INIT(&s->vtd_as_with_notifiers);
> > +    QLIST_INIT(&s->vtd_dev_icx_list);
> >      qemu_mutex_init(&s->iommu_lock);
> >      memset(s->vtd_as_by_bus_num, 0, sizeof(s->vtd_as_by_bus_num));
> >      memory_region_init_io(&s->csrmem, OBJECT(s), &vtd_mem_ops, s,
> > @@ -4155,6 +4520,8 @@ static void vtd_realize(DeviceState *dev, Error **errp)
> >                                       g_free, g_free);
> >      s->vtd_as_by_busptr = g_hash_table_new_full(vtd_uint64_hash,
> vtd_uint64_equal,
> >                                                g_free, g_free);
> > +    s->vtd_pasid_as = g_hash_table_new_full(vtd_pasid_as_key_hash,
> > +                                   vtd_pasid_as_key_equal, g_free, g_free);
> >      vtd_init(s);
> >      sysbus_mmio_map(SYS_BUS_DEVICE(s), 0,
> Q35_HOST_BRIDGE_IOMMU_ADDR);
> >      pci_setup_iommu(bus, &vtd_iommu_ops, dev);
> > diff --git a/hw/i386/intel_iommu_internal.h b/hw/i386/intel_iommu_internal.h
> > index 6c03560..18a9e50 100644
> > --- a/hw/i386/intel_iommu_internal.h
> > +++ b/hw/i386/intel_iommu_internal.h
> > @@ -311,6 +311,7 @@ typedef enum VTDFaultReason {
> >      VTD_FR_IR_SID_ERR = 0x26,   /* Invalid Source-ID */
> >
> >      VTD_FR_PASID_TABLE_INV = 0x58,  /*Invalid PASID table entry */
> > +    VTD_FR_PASID_ENTRY_P = 0x59, /* The Present(P) field of pasidt-entry is 0
> */
> >
> >      /* This is not a normal fault reason. We use this to indicate some faults
> >       * that are not referenced by the VT-d specification.
> > @@ -485,6 +486,19 @@ struct VTDRootEntry {
> >  };
> >  typedef struct VTDRootEntry VTDRootEntry;
> >
> > +struct VTDPASIDCacheInfo {
> > +#define VTD_PASID_CACHE_GLOBAL   (1ULL << 0)
> > +#define VTD_PASID_CACHE_DOMSI    (1ULL << 1)
> > +#define VTD_PASID_CACHE_PASIDSI  (1ULL << 2)
> > +    uint32_t flags;
> > +    uint16_t domain_id;
> > +    uint32_t pasid;
> > +};
> > +#define VTD_PASID_CACHE_INFO_MASK    (VTD_PASID_CACHE_GLOBAL | \
> > +                                      VTD_PASID_CACHE_DOMSI  | \
> > +                                      VTD_PASID_CACHE_PASIDSI)
> > +typedef struct VTDPASIDCacheInfo VTDPASIDCacheInfo;
> > +
> >  /* Masks for struct VTDRootEntry */
> >  #define VTD_ROOT_ENTRY_P            1ULL
> >  #define VTD_ROOT_ENTRY_CTP          (~0xfffULL)
> > diff --git a/hw/i386/trace-events b/hw/i386/trace-events
> > index f7cd4e5..87364a3 100644
> > --- a/hw/i386/trace-events
> > +++ b/hw/i386/trace-events
> > @@ -22,6 +22,7 @@ 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) "Domian slective PC invalidation
> domain 0x%"PRIx16
> >  vtd_pasid_cache_psi(uint16_t domain, uint32_t pasid) "PASID slective PC
> invalidation domain 0x%"PRIx16" pasid 0x%"PRIx32
> > diff --git a/include/hw/i386/intel_iommu.h b/include/hw/i386/intel_iommu.h
> > index 4158116..3cc4b74 100644
> > --- a/include/hw/i386/intel_iommu.h
> > +++ b/include/hw/i386/intel_iommu.h
> > @@ -69,6 +69,8 @@ typedef union VTD_IR_MSIAddress VTD_IR_MSIAddress;
> >  typedef struct VTDPASIDDirEntry VTDPASIDDirEntry;
> >  typedef struct VTDPASIDEntry VTDPASIDEntry;
> >  typedef struct VTDIOMMUContext VTDIOMMUContext;
> > +typedef struct VTDPASIDCacheEntry VTDPASIDCacheEntry;
> > +typedef struct VTDPASIDAddressSpace VTDPASIDAddressSpace;
> >
> >  /* Context-Entry */
> >  struct VTDContextEntry {
> > @@ -101,6 +103,31 @@ struct VTDPASIDEntry {
> >      uint64_t val[8];
> >  };
> >
> > +struct pasid_key {
> > +    uint32_t pasid;
> > +    uint16_t sid;
> > +};
> > +
> > +struct VTDPASIDCacheEntry {
> > +    /*
> > +     * The cache entry is obsolete if
> > +     * pasid_cache_gen!=IntelIOMMUState.pasid_cache_gen
> > +     */
> > +    uint32_t pasid_cache_gen;
> > +    struct VTDPASIDEntry pasid_entry;
> > +};
> > +
> > +struct VTDPASIDAddressSpace {
> > +    VTDBus *vtd_bus;
> > +    uint8_t devfn;
> > +    AddressSpace as;
> > +    uint32_t pasid;
> > +    IntelIOMMUState *iommu_state;
> > +    VTDContextCacheEntry context_cache_entry;
> > +    QLIST_ENTRY(VTDPASIDAddressSpace) next;
> > +    VTDPASIDCacheEntry pasid_cache_entry;
> 
> In vtd_pasid_cache_gsi() [1], you directly reset pasid_cache_gen for
> each pasid address space.  You never increase
> pasid_cache_entry.pasid_cache_gen.  Then IIUC the gen will always be
> either 0 or 1.  And...
> 
> > +};
> > +
> >  struct VTDAddressSpace {
> >      PCIBus *bus;
> >      uint8_t devfn;
> > @@ -122,6 +149,7 @@ struct VTDIOMMUContext {
> >      uint8_t devfn;
> >      IOMMUContext iommu_context;
> >      DualStageIOMMUObject *dsi_obj;
> > +    QLIST_ENTRY(VTDIOMMUContext) next;
> >      IntelIOMMUState *iommu_state;
> >  };
> >
> > @@ -272,9 +300,14 @@ struct IntelIOMMUState {
> >
> >      GHashTable *vtd_as_by_busptr;   /* VTDBus objects indexed by PCIBus*
> reference */
> >      VTDBus *vtd_as_by_bus_num[VTD_PCI_BUS_MAX]; /* VTDBus objects
> indexed by bus number */
> > +    GHashTable *vtd_pasid_as;   /* VTDPASIDAddressSpace instances */
> > +    uint32_t pasid_cache_gen;   /* Should be in [1,MAX] */
> 
> ... This should always be 1.
> IIUC you can drop both of the pasid_cache_gen, because in this whole
> patchset you'll remove the pasid hash entry when it is invalidated,
> right?  Then if the hash entry is there, it must be valid.  When it's
> out-dated, it'll be removed from the hash.

Oh, yes it is. However, it's not my intetion. I'd like to let [1] to
increase the s->pasid_cache_gen instead of justing zero it. I think it
will save some time as loop hash table takes time. Thanks for catching
it. :-)

Regards,
Yi Liu