Re: [Qemu-devel] [PATCH v3 05/12] hw/pci: introduce PCISVAOps to PCIDevice

[Liu, Yi L]

On Mon, Mar 05, 2018 at 02:31:44PM +1100, David Gibson wrote:
> On Thu, Mar 01, 2018 at 06:31:55PM +0800, Liu, Yi L wrote:
> > This patch intoduces PCISVAOps for virt-SVA.
> >
> > So far, to setup virt-SVA for assigned SVA capable device, needs to
> > config host translation structures. e.g. for VT-d, needs to set the
> > guest pasid table to host and enable nested translation. Besides,
> > vIOMMU emulator needs to forward guest's cache invalidation to host.
> > On VT-d, it is guest's invalidation to 1st level translation related
> > cache, such invalidation should be forwarded to host.
> >
> > Proposed PCISVAOps are:
> > * sva_bind_guest_pasid_table: set the guest pasid table to host, and
> >                               enable nested translation in host
> > * sva_register_notifier: register sva_notifier to forward guest's
> >                          cache invalidation to host
> > * sva_unregister_notifier: unregister sva_notifier
> >
> > The PCISVAOps should be provided by vfio or modules alike. Mainly for
> > assigned SVA capable devices.
> >
> > Take virt-SVA on VT-d as an exmaple:
> > If a guest wants to setup virt-SVA for an assigned SVA capable device,
> > it programs its context entry. vIOMMU emulator captures guest's context
> > entry programming, and figure out the target device. vIOMMU emulator
> > use the pci_device_sva_bind_pasid_table() API to bind the guest pasid
> > table to host.
> >
> > Guest would also program its pasid table. vIOMMU emulator captures
> > guest's pasid entry programming. In Qemu, needs to allocate an
> > AddressSpace to stand for the pasid tagged address space and Qemu also
> > needs to register sva_notifier to forward future cache invalidation
> > request to host.
> >
> > Allocating AddressSpace to stand for the pasid tagged address space is
> > for the emulation of emulated SVA capable devices. Emulated SVA capable
> > devices may issue SVA aware DMAs, Qemu needs to emulate read/write to a
> > pasid tagged AddressSpace. Thus needs an abstraction for such address
> > space in Qemu.
> >
> > Signed-off-by: Liu, Yi L <address@hidden>
>
> So PCISVAOps is roughly equivalent to the cluster-of-PASIDs context I
> was suggesting in my earlier comments,

yes, it is. The purpose is to expose pasid table bind and sva notfier
registration/unregistration to vIOMMU emulators.

> however it's only an ops
> structure.  That means you can't easily share a context between
> multiple PCI devices which is unfortunate because:
>     * The simplest use case for SVA I can see would just put the
>       same set of PASIDs into place for every SVA capable device

Do you mean for emulated SVA capable device?

>     * Sometimes the IOMMU can't determine exactly what device a DMA
>       came from.  Now the bridge cases where this applies are probably
>       unlikely with SVA devices, but I wouldn't want to bet on it.  In
>       addition, the chances some manufacturer will eventually put out
>       a buggy multifunction SVA capable device that use the wrong RIDs
>       for the secondary functions is pretty darn high.

I'm not sure I 100% got your point here. Do yu mean physical device?
In PCIE TLP, DMA packet should have a RID field? And it looks more like
a hardware layer trouble. For this series, it only provides necessary
software support to make sure guest's SVA operation is well prepared
before the SVA device issues the SVA aware DMA. e.g. link guest's pasid
table to host, and config iommu translation in nested mode.

>
> So I think instead you want a cluster-of-PASIDs object which has an
> ops table including both these and the per-PASID calls from the
> earlier patches (but the per-PASID calls would now take an explicit
> PASID value).

I didn't quite get "including both these and the per-PASID calls".
What do you mean by "these"? Do you mean the PCISVAOps?

Thanks,
Yi Liu
> > ---
> >  hw/pci/pci.c         | 60 
> > ++++++++++++++++++++++++++++++++++++++++++++++++++++
> >  include/hw/pci/pci.h | 21 ++++++++++++++++++
> >  2 files changed, 81 insertions(+)
> >
> > diff --git a/hw/pci/pci.c b/hw/pci/pci.c
> > index e006b6a..157fe21 100644
> > --- a/hw/pci/pci.c
> > +++ b/hw/pci/pci.c
> > @@ -2573,6 +2573,66 @@ void pci_setup_iommu(PCIBus *bus, PCIIOMMUFunc fn, 
> > void *opaque)
> >      bus->iommu_opaque = opaque;
> >  }
> >
> > +void pci_setup_sva_ops(PCIDevice *dev, PCISVAOps *ops)
> > +{
> > +    if (dev) {
> > +        dev->sva_ops = ops;
> > +    }
> > +    return;
> > +}
> > +
> > +void pci_device_sva_bind_pasid_table(PCIBus *bus,
> > +                     int32_t devfn, uint64_t addr, uint32_t size)
> > +{
> > +    PCIDevice *dev;
> > +
> > +    if (!bus) {
> > +        return;
> > +    }
> > +
> > +    dev = bus->devices[devfn];
> > +    if (dev && dev->sva_ops) {
> > +        dev->sva_ops->sva_bind_pasid_table(bus, devfn, addr, size);
> > +    }
> > +    return;
> > +}
> > +
> > +void pci_device_sva_register_notifier(PCIBus *bus, int32_t devfn,
> > +                                      IOMMUSVAContext *sva_ctx)
> > +{
> > +    PCIDevice *dev;
> > +
> > +    if (!bus) {
> > +        return;
> > +    }
> > +
> > +    dev = bus->devices[devfn];
> > +    if (dev && dev->sva_ops) {
> > +        dev->sva_ops->sva_register_notifier(bus,
> > +                                            devfn,
> > +                                            sva_ctx);
> > +    }
> > +    return;
> > +}
> > +
> > +void pci_device_sva_unregister_notifier(PCIBus *bus, int32_t devfn,
> > +                                        IOMMUSVAContext *sva_ctx)
> > +{
> > +    PCIDevice *dev;
> > +
> > +    if (!bus) {
> > +        return;
> > +    }
> > +
> > +    dev = bus->devices[devfn];
> > +    if (dev && dev->sva_ops) {
> > +        dev->sva_ops->sva_unregister_notifier(bus,
> > +                                              devfn,
> > +                                              sva_ctx);
> > +    }
> > +    return;
> > +}
> > +
> >  static void pci_dev_get_w64(PCIBus *b, PCIDevice *dev, void *opaque)
> >  {
> >      Range *range = opaque;
> > diff --git a/include/hw/pci/pci.h b/include/hw/pci/pci.h
> > index d8c18c7..32889a4 100644
> > --- a/include/hw/pci/pci.h
> > +++ b/include/hw/pci/pci.h
> > @@ -10,6 +10,8 @@
> >
> >  #include "hw/pci/pcie.h"
> >
> > +#include "hw/core/pasid.h"
> > +
> >  extern bool pci_available;
> >
> >  /* PCI bus */
> > @@ -262,6 +264,16 @@ struct PCIReqIDCache {
> >  };
> >  typedef struct PCIReqIDCache PCIReqIDCache;
> >
> > +typedef struct PCISVAOps PCISVAOps;
> > +struct PCISVAOps {
> > +    void (*sva_bind_pasid_table)(PCIBus *bus, int32_t devfn,
> > +             uint64_t pasidt_addr, uint32_t size);
> > +    void (*sva_register_notifier)(PCIBus *bus, int32_t devfn,
> > +                                  IOMMUSVAContext *sva_ctx);
> > +    void (*sva_unregister_notifier)(PCIBus *bus, int32_t devfn,
> > +                                    IOMMUSVAContext *sva_ctx);
> > +};
> > +
> >  struct PCIDevice {
> >      DeviceState qdev;
> >
> > @@ -351,6 +363,7 @@ struct PCIDevice {
> >      MSIVectorUseNotifier msix_vector_use_notifier;
> >      MSIVectorReleaseNotifier msix_vector_release_notifier;
> >      MSIVectorPollNotifier msix_vector_poll_notifier;
> > +    PCISVAOps *sva_ops;
> >  };
> >
> >  void pci_register_bar(PCIDevice *pci_dev, int region_num,
> > @@ -477,6 +490,14 @@ typedef AddressSpace *(*PCIIOMMUFunc)(PCIBus *, void 
> > *, int);
> >  AddressSpace *pci_device_iommu_address_space(PCIDevice *dev);
> >  void pci_setup_iommu(PCIBus *bus, PCIIOMMUFunc fn, void *opaque);
> >
> > +void pci_setup_sva_ops(PCIDevice *dev, PCISVAOps *ops);
> > +void pci_device_sva_bind_pasid_table(PCIBus *bus, int32_t devfn,
> > +                     uint64_t pasidt_addr, uint32_t size);
> > +void pci_device_sva_register_notifier(PCIBus *bus, int32_t devfn,
> > +                                      IOMMUSVAContext *sva_ctx);
> > +void pci_device_sva_unregister_notifier(PCIBus *bus, int32_t devfn,
> > +                                       IOMMUSVAContext *sva_ctx);
> > +
> >  static inline void
> >  pci_set_byte(uint8_t *config, uint8_t val)
> >  {