RE: [PATCH v2 07/22] intel_iommu: add set/unset_iommu_context callback

[Liu, Yi L]

Hi Eric,

> From: Auger Eric < address@hidden>
> Sent: Tuesday, March 31, 2020 4:24 AM
> To: Liu, Yi L <address@hidden>; address@hidden;
> Subject: Re: [PATCH v2 07/22] intel_iommu: add set/unset_iommu_context 
> callback
> 
> Yi,
> 
> On 3/30/20 6:24 AM, Liu Yi L wrote:
> > This patch adds set/unset_iommu_context() impelementation in Intel
> This patch implements the set/unset_iommu_context() ops for Intel vIOMMU.
> > vIOMMU. For Intel platform, pass-through modules (e.g. VFIO) could
> > set HostIOMMUContext to Intel vIOMMU emulator.
> >
> > Cc: Kevin Tian <address@hidden>
> > Cc: Jacob Pan <address@hidden>
> > Cc: Peter Xu <address@hidden>
> > Cc: Yi Sun <address@hidden>
> > Cc: Paolo Bonzini <address@hidden>
> > Cc: Richard Henderson <address@hidden>
> > Cc: Eduardo Habkost <address@hidden>
> > Signed-off-by: Liu Yi L <address@hidden>
> > ---
> >  hw/i386/intel_iommu.c         | 71
> ++++++++++++++++++++++++++++++++++++++++---
> >  include/hw/i386/intel_iommu.h | 21 ++++++++++---
> >  2 files changed, 83 insertions(+), 9 deletions(-)
> >
> > diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
> > index 4b22910..fd349c6 100644
> > --- a/hw/i386/intel_iommu.c
> > +++ b/hw/i386/intel_iommu.c
> > @@ -3354,23 +3354,33 @@ static const MemoryRegionOps vtd_mem_ir_ops = {
> >      },
> >  };
> >
> > -VTDAddressSpace *vtd_find_add_as(IntelIOMMUState *s, PCIBus *bus, int 
> > devfn)
> > +/**
> > + * Fetch a VTDBus instance for given PCIBus. If no existing instance,
> > + * allocate one.
> > + */
> > +static VTDBus *vtd_find_add_bus(IntelIOMMUState *s, PCIBus *bus)
> >  {
> >      uintptr_t key = (uintptr_t)bus;
> >      VTDBus *vtd_bus = g_hash_table_lookup(s->vtd_as_by_busptr, &key);
> > -    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 = g_malloc0(sizeof(VTDBus));
> >          vtd_bus->bus = bus;
> >          g_hash_table_insert(s->vtd_as_by_busptr, new_key, vtd_bus);
> >      }
> > +    return vtd_bus;
> > +}
> >
> > +VTDAddressSpace *vtd_find_add_as(IntelIOMMUState *s, PCIBus *bus, int 
> > devfn)
> > +{
> > +    VTDBus *vtd_bus;
> > +    VTDAddressSpace *vtd_dev_as;
> > +    char name[128];
> > +
> > +    vtd_bus = vtd_find_add_bus(s, bus);
> >      vtd_dev_as = vtd_bus->dev_as[devfn];
> >
> >      if (!vtd_dev_as) {
> > @@ -3436,6 +3446,55 @@ VTDAddressSpace
> *vtd_find_add_as(IntelIOMMUState *s, PCIBus *bus, int devfn)
> >      return vtd_dev_as;
> >  }
> >
> > +static int vtd_dev_set_iommu_context(PCIBus *bus, void *opaque,
> > +                                     int devfn,
> > +                                     HostIOMMUContext *iommu_ctx)
> > +{
> > +    IntelIOMMUState *s = opaque;
> > +    VTDBus *vtd_bus;
> > +    VTDHostIOMMUContext *vtd_dev_icx;
> > +
> > +    assert(0 <= devfn && devfn < PCI_DEVFN_MAX);
> > +
> > +    vtd_bus = vtd_find_add_bus(s, bus);
> > +
> > +    vtd_iommu_lock(s);
> > +
> > +    vtd_dev_icx = vtd_bus->dev_icx[devfn];
> > +
> > +    assert(!vtd_dev_icx);
> > +
> > +    vtd_bus->dev_icx[devfn] = vtd_dev_icx =
> > +                    g_malloc0(sizeof(VTDHostIOMMUContext));
> > +    vtd_dev_icx->vtd_bus = vtd_bus;
> > +    vtd_dev_icx->devfn = (uint8_t)devfn;
> > +    vtd_dev_icx->iommu_state = s;
> > +    vtd_dev_icx->iommu_ctx = iommu_ctx;
> > +
> > +    vtd_iommu_unlock(s);
> > +
> > +    return 0;
> > +}
> > +
> > +static void vtd_dev_unset_iommu_context(PCIBus *bus, void *opaque, int 
> > devfn)
> > +{
> > +    IntelIOMMUState *s = opaque;
> > +    VTDBus *vtd_bus;
> > +    VTDHostIOMMUContext *vtd_dev_icx;
> > +
> > +    assert(0 <= devfn && devfn < PCI_DEVFN_MAX);
> > +
> > +    vtd_bus = vtd_find_add_bus(s, bus);
> > +
> > +    vtd_iommu_lock(s);
> > +
> > +    vtd_dev_icx = vtd_bus->dev_icx[devfn];
> > +    g_free(vtd_dev_icx);
> > +    vtd_bus->dev_icx[devfn] = NULL;
> > +
> > +    vtd_iommu_unlock(s);
> > +}
> > +
> >  static uint64_t get_naturally_aligned_size(uint64_t start,
> >                                             uint64_t size, int gaw)
> >  {
> > @@ -3731,6 +3790,8 @@ static AddressSpace *vtd_host_dma_iommu(PCIBus
> *bus, void *opaque, int devfn)
> >
> >  static PCIIOMMUOps vtd_iommu_ops = {
> >      .get_address_space = vtd_host_dma_iommu,
> > +    .set_iommu_context = vtd_dev_set_iommu_context,
> > +    .unset_iommu_context = vtd_dev_unset_iommu_context,
> >  };
> >
> >  static bool vtd_decide_config(IntelIOMMUState *s, Error **errp)
> > diff --git a/include/hw/i386/intel_iommu.h b/include/hw/i386/intel_iommu.h
> > index 3870052..b5fefb9 100644
> > --- a/include/hw/i386/intel_iommu.h
> > +++ b/include/hw/i386/intel_iommu.h
> > @@ -64,6 +64,7 @@ typedef union VTD_IR_TableEntry VTD_IR_TableEntry;
> >  typedef union VTD_IR_MSIAddress VTD_IR_MSIAddress;
> >  typedef struct VTDPASIDDirEntry VTDPASIDDirEntry;
> >  typedef struct VTDPASIDEntry VTDPASIDEntry;
> > +typedef struct VTDHostIOMMUContext VTDHostIOMMUContext;
> >
> >  /* Context-Entry */
> >  struct VTDContextEntry {
> > @@ -112,10 +113,20 @@ struct VTDAddressSpace {
> >      IOVATree *iova_tree;          /* Traces mapped IOVA ranges */
> >  };
> >
> > +struct VTDHostIOMMUContext {
> 
> 
> > +    VTDBus *vtd_bus;
> > +    uint8_t devfn;
> > +    HostIOMMUContext *iommu_ctx;
> I don't get why we don't have standard QOM inheritance instead of this
> handle?
> VTDHostContext parent_obj;
> 
> like IOMMUMemoryRegion <- MemoryRegion <- Object

Here it is not inherit the object. It's just cache the HostIOMMUContext
pointer in vIOMMU. Just like AddressSpace, it has a MemoryRegion pointer.
Here is the same, VTDHostIOMMUContext is just a wrapper to better manage
it in vVT-d. It's not inheriting.

> > +    IntelIOMMUState *iommu_state;
> > +};
> > +
> >  struct VTDBus {
> > -    PCIBus* bus;           /* A reference to the bus to provide 
> > translation for
> */
> > +    /* A reference to the bus to provide translation for */
> > +    PCIBus *bus;
> >      /* A table of VTDAddressSpace objects indexed by devfn */
> > -    VTDAddressSpace *dev_as[];
> > +    VTDAddressSpace *dev_as[PCI_DEVFN_MAX];
> > +    /* A table of VTDHostIOMMUContext objects indexed by devfn */
> > +    VTDHostIOMMUContext *dev_icx[PCI_DEVFN_MAX];
> At this point of the review, it is unclear to me why the context is
> associated to a device.

HostIOMMUContext can be per-device or not. It depends on how vIOMMU
manage it. For vVT-d, it's per device as the container is per-device.

> Up to now you have not explained it should. If
> so why isn't it part of VTDAddressSpace?

Ah, I did have considered it. But I chose to use a separate one as
context is not really tied with an addresspace. It's better to mange
it with a separate structure.

Regards,
Yi Liu