RE: [PATCH v1 07/22] intel_iommu: add set/unset_iommu_context callback

Liu, Yi L
2020-03-24T11:15:31Z

> From: Peter Xu <peterx@redhat.com>
> Sent: Tuesday, March 24, 2020 5:29 AM
> To: Liu, Yi L <yi.l.liu@intel.com>
> Subject: Re: [PATCH v1 07/22] intel_iommu: add set/unset_iommu_context
> callback
>
> On Sun, Mar 22, 2020 at 05:36:04AM -0700, Liu Yi L wrote:
> > This patch adds set/unset_iommu_context() impelementation in Intel
> > vIOMMU. For Intel platform, pass-through modules (e.g. VFIO) could
> > set HostIOMMUContext to Intel vIOMMU emulator.
> >
> > 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 | 70
> +++++++++++++++++++++++++++++++++++++++----
> > include/hw/i386/intel_iommu.h | 17 +++++++++--
> > 2 files changed, 80 insertions(+), 7 deletions(-)
> >
> > diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
> > index 4b22910..8d9204f 100644
> > --- a/hw/i386/intel_iommu.c
> > +++ b/hw/i386/intel_iommu.c
> > @@ -3354,23 +3354,35 @@ 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) + PCI_DEVFN_MAX * \
> > + (sizeof(VTDAddressSpace *) + \
> > + sizeof(VTDHostIOMMUContext *)));
>
> IIRC I commented on this before... Shouldn't sizeof(VTDBus) be
> enough?

Right. My bad. Will do it in next version.

> > 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 +3448,52 @@ 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 *host_icx)
> > +{
> > + 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];
> > +
> > + if (!vtd_dev_icx) {
>
> We can assert this directly I think, in case we accidentally set the
> context twice without notice.

good idea. will add it.

>
> > + 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->host_icx = host_icx;
> > + }
> > + 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);
>
> Better set it as NULL, and can also drop vtd_dev_icx which seems
> meaningless..

right. it's missed.

> g_free(vtd_bus->dev_icx[devfn]);
> 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 +3789,8 @@ 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..9b4fc0a 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 *host_icx;
> > + 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];
> > };
> >
> > struct VTDIOTLBEntry {
> > @@ -271,6 +282,8 @@ struct IntelIOMMUState {
> > /*
> > * Protects IOMMU states in general. Currently it protects the
> > * per-IOMMU IOTLB cache, and context entry cache in VTDAddressSpace.
> > + * Protect the update/usage of HostIOMMUContext pointer cached in
> > + * VTDBus->dev_icx array as array elements may be updated by hotplug
>
> I think the context update does not need to be updated, because they
> should always be with the BQL, right?

Hmmmm, maybe I used bad description. My purpose is to protect the stored
HostIOMMUContext pointer in vIOMMU. With pci_device_set/unset_iommu_context,
vIOMMU have a copy of HostIOMMUContext. If VFIO container is released
(e.g. hotpulg out device), HostIOMMUContext will alos be released. This
will trigger the pci_device_unset_iommu_context() to clean the copy. To
avoid using a staled HostIOMMUContext in vIOMMU, vIOMMU should have a
lock to block the pci_device_unset_iommu_context() calling until other
threads finished their HostIOMMUContext usage. Do you want a description
update here or other preference?

Regards,
Yi Liu