Re: [PATCH V2 2/4] intel-iommu: drop VTDBus

[Peter Xu <peterx@redhat.com>]

On Fri, Apr 22, 2022 at 02:26:11PM +0800, Jason Wang wrote:
> On Fri, Apr 22, 2022 at 9:17 AM Peter Xu <peterx@redhat.com> wrote:
> >
> > Hi, Jason,
> >
> > Mostly good to me, just a few nitpicks below.
> >
> > On Mon, Mar 21, 2022 at 01:54:27PM +0800, Jason Wang wrote:
> > > We introduce VTDBus structure as an intermediate step for searching
> > > the address space. This works well with SID based matching/lookup. But
> > > when we want to support SID plus PASID based address space lookup,
> > > this intermediate steps turns out to be a burden. So the patch simply
> > > drops the VTDBus structure and use the PCIBus and devfn as the key for
> > > the g_hash_table(). This simplifies the codes and the future PASID
> > > extension.
> > >
> > > To prevent being slower for past vtd_find_as_from_bus_num() callers, a
> > > vtd_as cache indexed by the bus number is introduced to store the last
> > > recent search result of a vtd_as belongs to a specific bus.
> > >
> > > Signed-off-by: Jason Wang <jasowang@redhat.com>
> > > ---
> > >  hw/i386/intel_iommu.c         | 238 +++++++++++++++++-----------------
> > >  include/hw/i386/intel_iommu.h |  11 +-
> > >  2 files changed, 123 insertions(+), 126 deletions(-)
> > >
> > > diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
> > > index 90964b201c..5851a17d0e 100644
> > > --- a/hw/i386/intel_iommu.c
> > > +++ b/hw/i386/intel_iommu.c
> > > @@ -61,6 +61,16 @@
> > >      }                                                                         \
> > >  }
> > >
> > > +/*
> > > + * PCI bus number (or SID) is not reliable since the device is usaully
> > > + * initalized before guest can configure the PCI bridge
> > > + * (SECONDARY_BUS_NUMBER).
> > > + */
> > > +struct vtd_as_key {
> > > +    PCIBus *bus;
> > > +    uint8_t devfn;
> > > +};
> > > +
> > >  static void vtd_address_space_refresh_all(IntelIOMMUState *s);
> > >  static void vtd_address_space_unmap(VTDAddressSpace *as, IOMMUNotifier *n);
> > >
> > > @@ -210,6 +220,31 @@ static guint vtd_uint64_hash(gconstpointer v)
> > >      return (guint)*(const uint64_t *)v;
> > >  }
> > >
> > > +static gboolean vtd_as_equal(gconstpointer v1, gconstpointer v2)
> > > +{
> > > +    const struct vtd_as_key *key1 = v1;
> > > +    const struct vtd_as_key *key2 = v2;
> > > +
> > > +    return (key1->bus == key2->bus) && (key1->devfn == key2->devfn);
> > > +}
> > > +
> > > +static inline uint16_t vtd_make_source_id(uint8_t bus_num, uint8_t devfn)
> > > +{
> > > +    return ((bus_num & 0xffUL) << 8) | (devfn & 0xffUL);
> > > +}
> >
> > Nit: we could directly drop this one and use PCI_BUILD_BDF().
> 
> Will fix.
> 
> >
> > > +
> > > +/*
> > > + * Note that we use pointer to PCIBus as the key, so hashing/shifting
> > > + * based on the pointer value is intended.
> >
> > Thanks for the comment; that helps.
> >
> > Should we also mention that this hash is not the only interface to identify
> > two vtd_as*, say, even if on a 32bit system we got last 24 bits collapsed
> > on two vtd_as* pointers, we can still have vtd_as_equal() to guard us?
> 
> Ok. let me add that in the next version.
> 
> >
> > > + */
> > > +static guint vtd_as_hash(gconstpointer v)
> > > +{
> > > +    const struct vtd_as_key *key = v;
> > > +    guint value = (guint)(uintptr_t)key->bus;
> > > +
> > > +    return (guint)(value << 8 | key->devfn);
> > > +}
> > > +
> > >  static gboolean vtd_hash_remove_by_domain(gpointer key, gpointer value,
> > >                                            gpointer user_data)
> > >  {
> > > @@ -248,22 +283,14 @@ static gboolean vtd_hash_remove_by_page(gpointer key, gpointer value,
> > >  static void vtd_reset_context_cache_locked(IntelIOMMUState *s)
> > >  {
> > >      VTDAddressSpace *vtd_as;
> > > -    VTDBus *vtd_bus;
> > > -    GHashTableIter bus_it;
> > > -    uint32_t devfn_it;
> > > +    GHashTableIter as_it;
> > >
> > >      trace_vtd_context_cache_reset();
> > >
> > > -    g_hash_table_iter_init(&bus_it, s->vtd_as_by_busptr);
> > > +    g_hash_table_iter_init(&as_it, s->vtd_as);
> > >
> > > -    while (g_hash_table_iter_next (&bus_it, NULL, (void**)&vtd_bus)) {
> > > -        for (devfn_it = 0; devfn_it < PCI_DEVFN_MAX; ++devfn_it) {
> > > -            vtd_as = vtd_bus->dev_as[devfn_it];
> > > -            if (!vtd_as) {
> > > -                continue;
> > > -            }
> > > -            vtd_as->context_cache_entry.context_cache_gen = 0;
> > > -        }
> > > +    while (g_hash_table_iter_next (&as_it, NULL, (void**)&vtd_as)) {
> > > +        vtd_as->context_cache_entry.context_cache_gen = 0;
> > >      }
> > >      s->context_cache_gen = 1;
> > >  }
> > > @@ -993,32 +1020,6 @@ static bool vtd_slpte_nonzero_rsvd(uint64_t slpte, uint32_t level)
> > >      return slpte & rsvd_mask;
> > >  }
> > >
> > > -/* Find the VTD address space associated with a given bus number */
> > > -static VTDBus *vtd_find_as_from_bus_num(IntelIOMMUState *s, uint8_t bus_num)
> > > -{
> > > -    VTDBus *vtd_bus = s->vtd_as_by_bus_num[bus_num];
> > > -    GHashTableIter iter;
> > > -
> > > -    if (vtd_bus) {
> > > -        return vtd_bus;
> > > -    }
> > > -
> > > -    /*
> > > -     * Iterate over the registered buses to find the one which
> > > -     * currently holds this bus number and update the bus_num
> > > -     * lookup table.
> > > -     */
> > > -    g_hash_table_iter_init(&iter, s->vtd_as_by_busptr);
> > > -    while (g_hash_table_iter_next(&iter, NULL, (void **)&vtd_bus)) {
> > > -        if (pci_bus_num(vtd_bus->bus) == bus_num) {
> > > -            s->vtd_as_by_bus_num[bus_num] = vtd_bus;
> > > -            return vtd_bus;
> > > -        }
> > > -    }
> > > -
> > > -    return NULL;
> > > -}
> > > -
> > >  /* Given the @iova, get relevant @slptep. @slpte_level will be the last level
> > >   * of the translation, can be used for deciding the size of large page.
> > >   */
> > > @@ -1634,24 +1635,13 @@ static bool vtd_switch_address_space(VTDAddressSpace *as)
> > >
> > >  static void vtd_switch_address_space_all(IntelIOMMUState *s)
> > >  {
> > > +    VTDAddressSpace *vtd_as;
> > >      GHashTableIter iter;
> > > -    VTDBus *vtd_bus;
> > > -    int i;
> > > -
> > > -    g_hash_table_iter_init(&iter, s->vtd_as_by_busptr);
> > > -    while (g_hash_table_iter_next(&iter, NULL, (void **)&vtd_bus)) {
> > > -        for (i = 0; i < PCI_DEVFN_MAX; i++) {
> > > -            if (!vtd_bus->dev_as[i]) {
> > > -                continue;
> > > -            }
> > > -            vtd_switch_address_space(vtd_bus->dev_as[i]);
> > > -        }
> > > -    }
> > > -}
> > >
> > > -static inline uint16_t vtd_make_source_id(uint8_t bus_num, uint8_t devfn)
> > > -{
> > > -    return ((bus_num & 0xffUL) << 8) | (devfn & 0xffUL);
> > > +    g_hash_table_iter_init(&iter, s->vtd_as);
> > > +    while (g_hash_table_iter_next(&iter, NULL, (void **)&vtd_as)) {
> > > +        vtd_switch_address_space(vtd_as);
> > > +    }
> > >  }
> > >
> > >  static const bool vtd_qualified_faults[] = {
> > > @@ -1688,18 +1678,39 @@ static inline bool vtd_is_interrupt_addr(hwaddr addr)
> > >      return VTD_INTERRUPT_ADDR_FIRST <= addr && addr <= VTD_INTERRUPT_ADDR_LAST;
> > >  }
> > >
> > > +static gboolean vtd_find_as_by_sid(gpointer key, gpointer value,
> > > +                                   gpointer user_data)
> > > +{
> > > +    struct vtd_as_key *as_key = (struct vtd_as_key *)key;
> > > +    uint16_t target_sid = *(uint16_t *)user_data;
> > > +    uint16_t sid = vtd_make_source_id(pci_bus_num(as_key->bus),
> > > +                                      as_key->devfn);
> > > +    return sid == target_sid;
> > > +}
> > > +
> > > +static VTDAddressSpace *vtd_get_as_by_sid(IntelIOMMUState *s, uint16_t sid)
> > > +{
> > > +    uint8_t bus_num = sid >> 8;
> >
> > PCI_BUS_NUM(sid)?
> 
> Will do.
> 
> >
> > > +    VTDAddressSpace *vtd_as = s->vtd_as_cache[bus_num];
> > > +
> > > +    if (vtd_as &&
> > > +        (sid == vtd_make_source_id(pci_bus_num(vtd_as->bus),
> > > +                                   vtd_as->devfn))) {
> > > +        return vtd_as;
> > > +    }
> > > +
> > > +    vtd_as = g_hash_table_find(s->vtd_as, vtd_find_as_by_sid, &sid);
> > > +    s->vtd_as_cache[bus_num] = vtd_as;
> > > +
> > > +    return vtd_as;
> > > +}
> > > +
> > >  static void vtd_pt_enable_fast_path(IntelIOMMUState *s, uint16_t source_id)
> > >  {
> > > -    VTDBus *vtd_bus;
> > >      VTDAddressSpace *vtd_as;
> > >      bool success = false;
> > >
> > > -    vtd_bus = vtd_find_as_from_bus_num(s, VTD_SID_TO_BUS(source_id));
> > > -    if (!vtd_bus) {
> > > -        goto out;
> > > -    }
> > > -
> > > -    vtd_as = vtd_bus->dev_as[VTD_SID_TO_DEVFN(source_id)];
> > > +    vtd_as = vtd_get_as_by_sid(s, source_id);
> > >      if (!vtd_as) {
> > >          goto out;
> > >      }
> > > @@ -1907,11 +1918,10 @@ static void vtd_context_device_invalidate(IntelIOMMUState *s,
> > >                                            uint16_t source_id,
> > >                                            uint16_t func_mask)
> > >  {
> > > +    GHashTableIter as_it;
> > >      uint16_t mask;
> > > -    VTDBus *vtd_bus;
> > >      VTDAddressSpace *vtd_as;
> > >      uint8_t bus_n, devfn;
> > > -    uint16_t devfn_it;
> > >
> > >      trace_vtd_inv_desc_cc_devices(source_id, func_mask);
> > >
> > > @@ -1934,32 +1944,31 @@ static void vtd_context_device_invalidate(IntelIOMMUState *s,
> > >      mask = ~mask;
> > >
> > >      bus_n = VTD_SID_TO_BUS(source_id);
> > > -    vtd_bus = vtd_find_as_from_bus_num(s, bus_n);
> > > -    if (vtd_bus) {
> > > -        devfn = VTD_SID_TO_DEVFN(source_id);
> > > -        for (devfn_it = 0; devfn_it < PCI_DEVFN_MAX; ++devfn_it) {
> > > -            vtd_as = vtd_bus->dev_as[devfn_it];
> > > -            if (vtd_as && ((devfn_it & mask) == (devfn & mask))) {
> > > -                trace_vtd_inv_desc_cc_device(bus_n, VTD_PCI_SLOT(devfn_it),
> > > -                                             VTD_PCI_FUNC(devfn_it));
> > > -                vtd_iommu_lock(s);
> > > -                vtd_as->context_cache_entry.context_cache_gen = 0;
> > > -                vtd_iommu_unlock(s);
> > > -                /*
> > > -                 * Do switch address space when needed, in case if the
> > > -                 * device passthrough bit is switched.
> > > -                 */
> > > -                vtd_switch_address_space(vtd_as);
> > > -                /*
> > > -                 * So a device is moving out of (or moving into) a
> > > -                 * domain, resync the shadow page table.
> > > -                 * This won't bring bad even if we have no such
> > > -                 * notifier registered - the IOMMU notification
> > > -                 * framework will skip MAP notifications if that
> > > -                 * happened.
> > > -                 */
> > > -                vtd_sync_shadow_page_table(vtd_as);
> > > -            }
> > > +    devfn = VTD_SID_TO_DEVFN(source_id);
> > > +
> > > +    g_hash_table_iter_init(&as_it, s->vtd_as);
> > > +    while (g_hash_table_iter_next(&as_it, NULL, (void**)&vtd_as)) {
> > > +        if ((pci_bus_num(vtd_as->bus) == bus_n) &&
> > > +            (vtd_as->devfn & mask) == (devfn & mask)) {
> > > +            trace_vtd_inv_desc_cc_device(bus_n, VTD_PCI_SLOT(vtd_as->devfn),
> > > +                                         VTD_PCI_FUNC(vtd_as->devfn));
> > > +            vtd_iommu_lock(s);
> > > +            vtd_as->context_cache_entry.context_cache_gen = 0;
> > > +            vtd_iommu_unlock(s);
> > > +            /*
> > > +             * Do switch address space when needed, in case if the
> > > +             * device passthrough bit is switched.
> > > +             */
> > > +            vtd_switch_address_space(vtd_as);
> > > +            /*
> > > +             * So a device is moving out of (or moving into) a
> > > +             * domain, resync the shadow page table.
> > > +             * This won't bring bad even if we have no such
> > > +             * notifier registered - the IOMMU notification
> > > +             * framework will skip MAP notifications if that
> > > +             * happened.
> > > +             */
> > > +            vtd_sync_shadow_page_table(vtd_as);
> > >          }
> > >      }
> > >  }
> > > @@ -2473,18 +2482,13 @@ static bool vtd_process_device_iotlb_desc(IntelIOMMUState *s,
> > >  {
> > >      VTDAddressSpace *vtd_dev_as;
> > >      IOMMUTLBEvent event;
> > > -    struct VTDBus *vtd_bus;
> > >      hwaddr addr;
> > >      uint64_t sz;
> > >      uint16_t sid;
> > > -    uint8_t devfn;
> > >      bool size;
> > > -    uint8_t bus_num;
> > >
> > >      addr = VTD_INV_DESC_DEVICE_IOTLB_ADDR(inv_desc->hi);
> > >      sid = VTD_INV_DESC_DEVICE_IOTLB_SID(inv_desc->lo);
> > > -    devfn = sid & 0xff;
> > > -    bus_num = sid >> 8;
> > >      size = VTD_INV_DESC_DEVICE_IOTLB_SIZE(inv_desc->hi);
> > >
> > >      if ((inv_desc->lo & VTD_INV_DESC_DEVICE_IOTLB_RSVD_LO) ||
> > > @@ -2495,12 +2499,11 @@ static bool vtd_process_device_iotlb_desc(IntelIOMMUState *s,
> > >          return false;
> > >      }
> > >
> > > -    vtd_bus = vtd_find_as_from_bus_num(s, bus_num);
> > > -    if (!vtd_bus) {
> > > -        goto done;
> > > -    }
> > > -
> > > -    vtd_dev_as = vtd_bus->dev_as[devfn];
> > > +    /*
> > > +     * Using sid is OK since the guest should have finished the
> > > +     * initialization of both the bus and device.
> > > +     */
> > > +    vtd_dev_as = vtd_get_as_by_sid(s, sid);
> > >      if (!vtd_dev_as) {
> > >          goto done;
> > >      }
> > > @@ -3426,27 +3429,27 @@ static const MemoryRegionOps vtd_mem_ir_ops = {
> > >
> > >  VTDAddressSpace *vtd_find_add_as(IntelIOMMUState *s, PCIBus *bus, int devfn)
> > >  {
> > > -    uintptr_t key = (uintptr_t)bus;
> > > -    VTDBus *vtd_bus = g_hash_table_lookup(s->vtd_as_by_busptr, &key);
> > > +    /*
> > > +     * We can't simply use sid here since the bus number might not be
> > > +     * initialized by the guest.
> > > +     */
> > > +    struct vtd_as_key key = {
> > > +        .bus = bus,
> > > +        .devfn = devfn,
> > > +    };
> > >      VTDAddressSpace *vtd_dev_as;
> > >      char name[128];
> > >
> > > -    if (!vtd_bus) {
> > > -        uintptr_t *new_key = g_malloc(sizeof(*new_key));
> > > -        *new_key = (uintptr_t)bus;
> > > -        /* No corresponding free() */
> > > -        vtd_bus = g_malloc0(sizeof(VTDBus) + sizeof(VTDAddressSpace *) * \
> > > -                            PCI_DEVFN_MAX);
> > > -        vtd_bus->bus = bus;
> > > -        g_hash_table_insert(s->vtd_as_by_busptr, new_key, vtd_bus);
> > > -    }
> > > +    vtd_dev_as = g_hash_table_lookup(s->vtd_as, &key);
> > > +    if (!vtd_dev_as) {
> > > +        struct vtd_as_key *new_key = g_malloc(sizeof(*new_key));
> > >
> > > -    vtd_dev_as = vtd_bus->dev_as[devfn];
> > > +        new_key->bus = bus;
> > > +        new_key->devfn = devfn;
> > >
> > > -    if (!vtd_dev_as) {
> > >          snprintf(name, sizeof(name), "vtd-%02x.%x", PCI_SLOT(devfn),
> > >                   PCI_FUNC(devfn));
> > > -        vtd_bus->dev_as[devfn] = vtd_dev_as = g_malloc0(sizeof(VTDAddressSpace));
> > > +        vtd_dev_as = g_malloc0(sizeof(VTDAddressSpace));
> > >
> > >          vtd_dev_as->bus = bus;
> > >          vtd_dev_as->devfn = (uint8_t)devfn;
> > > @@ -3502,6 +3505,8 @@ VTDAddressSpace *vtd_find_add_as(IntelIOMMUState *s, PCIBus *bus, int devfn)
> > >                                              &vtd_dev_as->nodmar, 0);
> > >
> > >          vtd_switch_address_space(vtd_dev_as);
> > > +
> > > +        g_hash_table_insert(s->vtd_as, new_key, vtd_dev_as);
> > >      }
> > >      return vtd_dev_as;
> > >  }
> > > @@ -3875,7 +3880,6 @@ static void vtd_realize(DeviceState *dev, Error **errp)
> > >
> > >      QLIST_INIT(&s->vtd_as_with_notifiers);
> > >      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,
> > >                            "intel_iommu", DMAR_REG_SIZE);
> > >
> > > @@ -3897,8 +3901,8 @@ static void vtd_realize(DeviceState *dev, Error **errp)
> > >      /* No corresponding destroy */
> > >      s->iotlb = g_hash_table_new_full(vtd_uint64_hash, vtd_uint64_equal,
> > >                                       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_as = g_hash_table_new_full(vtd_as_hash, vtd_as_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_host_dma_iommu, dev);
> > > diff --git a/include/hw/i386/intel_iommu.h b/include/hw/i386/intel_iommu.h
> > > index 3b5ac869db..fa1bed353c 100644
> > > --- a/include/hw/i386/intel_iommu.h
> > > +++ b/include/hw/i386/intel_iommu.h
> > > @@ -58,7 +58,6 @@ typedef struct VTDContextEntry VTDContextEntry;
> > >  typedef struct VTDContextCacheEntry VTDContextCacheEntry;
> > >  typedef struct VTDAddressSpace VTDAddressSpace;
> > >  typedef struct VTDIOTLBEntry VTDIOTLBEntry;
> > > -typedef struct VTDBus VTDBus;
> > >  typedef union VTD_IR_TableEntry VTD_IR_TableEntry;
> > >  typedef union VTD_IR_MSIAddress VTD_IR_MSIAddress;
> > >  typedef struct VTDPASIDDirEntry VTDPASIDDirEntry;
> > > @@ -111,12 +110,6 @@ struct VTDAddressSpace {
> > >      IOVATree *iova_tree;          /* Traces mapped IOVA ranges */
> > >  };
> > >
> > > -struct VTDBus {
> > > -    PCIBus* bus;             /* A reference to the bus to provide translation for */
> > > -    /* A table of VTDAddressSpace objects indexed by devfn */
> > > -    VTDAddressSpace *dev_as[];
> > > -};
> > > -
> > >  struct VTDIOTLBEntry {
> > >      uint64_t gfn;
> > >      uint16_t domain_id;
> > > @@ -253,8 +246,8 @@ struct IntelIOMMUState {
> > >      uint32_t context_cache_gen;     /* Should be in [1,MAX] */
> > >      GHashTable *iotlb;              /* IOTLB */
> > >
> > > -    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_as;             /* VTD address space indexed by source id*/
> >
> > It's not indexed by source ID but vtd_as_key?
> 
> Right, let me fix that.
> 
> >
> > Meanwhile how about renaming it to vtd_address_spaces?  Since we use vtd_as
> > as the name for VTDAddressSpace* in most code paths, so imho it'll be
> > easier to identify the two.
> 
> Ok.

If with all above nitpicks fixed, please feel free to add:

Reviewed-by: Peter Xu <peterx@redhat.com>

Thanks!

-- 
Peter Xu