Re: [Qemu-devel] [PATCH qemu v4 2/3] vfio/spapr: Add a notifier for PPC64 HV/PR KVM about new group attached to LIOBN

[Alexey Kardashevskiy]

On 25/08/17 16:21, David Gibson wrote:
> On Thu, Jul 20, 2017 at 05:22:30PM +1000, Alexey Kardashevskiy wrote:
>> This implements a notification for a new IOMMU group attached to
>> sPAPR's logical IO bus (LIOBN) to enable in-kernel TCE acceleration.
>>
>> This extends the TYPE_SPAPR_IOMMU_MEMORY_REGION class with a get_fd()
>> callback which returns KVM fd associated with LIOBN, the notifier uses it
>> to establish link between LIOBN and IOMMU group in the KVM.
>>
>> Signed-off-by: Alexey Kardashevskiy <address@hidden>
>> ---
>>
>> The practical reason for adding get_fd() as a callback is avoiding static
>> linking to spapt_tce_get_fd(): hw/vfio/spapr.c compiles when
>> CONFIG_SOFTMMU=y to avoid multiple "ifdef PSERIES"'s in the rest
>> of VFIO code but hw/ppc/spapr_iommu.c (where spapt_tce_get_fd() besides)
>> compiles only when CONFIG_PSERIES=y.
> 
> Ok.  Nonetheless I don't think the get_fd() method is a good idea.
> First, it's basically an abstraction violation, exposing the region's
> internal fd.  Second, it's a method which only plausibly has one
> implementation which is rarely sensible.
> 
> What this comes down to is that the guest IOMMU mechanism needs
> information about host vfio groups mapped - for an optimization in
> this case.
> 
> So what would make sense to me is to put an "add_vfio_group" method
> into IOMMUMemoryRegionClass (or even MemoryRegionClass).  In most
> cases that will be NULL (== no-op).  For the spapr IOMMU region, it
> will (attempt to) connect the host group to the guest liobn.


Like this?

IOMMUMemoryRegionClass::add_vfio_group_kvm(int kvm_device_fd, int groupfd);

It is just cleaner to keep kvm_device_fd and its ioclts() in the same place
but ok.


> 
>> ---
>>  include/hw/ppc/spapr.h        | 15 +++++++++++++++
>>  include/hw/vfio/vfio-common.h |  2 ++
>>  hw/ppc/spapr_iommu.c          | 10 ++++++++++
>>  hw/vfio/common.c              | 10 ++++++++++
>>  hw/vfio/spapr.c               | 39 +++++++++++++++++++++++++++++++++++++++
>>  hw/vfio/trace-events          |  1 +
>>  6 files changed, 77 insertions(+)
>>
>> diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
>> index 2a303a705c..c1d37e6356 100644
>> --- a/include/hw/ppc/spapr.h
>> +++ b/include/hw/ppc/spapr.h
>> @@ -591,6 +591,7 @@ void spapr_load_rtas(sPAPRMachineState *spapr, void 
>> *fdt, hwaddr addr);
>>  #define RTAS_EVENT_SCAN_RATE    1
>>  
>>  typedef struct sPAPRTCETable sPAPRTCETable;
>> +typedef struct sPAPRIOMMUMemoryRegionClass sPAPRIOMMUMemoryRegionClass;
>>  
>>  #define TYPE_SPAPR_TCE_TABLE "spapr-tce-table"
>>  #define SPAPR_TCE_TABLE(obj) \
>> @@ -599,6 +600,12 @@ typedef struct sPAPRTCETable sPAPRTCETable;
>>  #define TYPE_SPAPR_IOMMU_MEMORY_REGION "spapr-iommu-memory-region"
>>  #define SPAPR_IOMMU_MEMORY_REGION(obj) \
>>          OBJECT_CHECK(IOMMUMemoryRegion, (obj), 
>> TYPE_SPAPR_IOMMU_MEMORY_REGION)
>> +#define SPAPR_IOMMU_MEMORY_REGION_GET_CLASS(obj) \
>> +        OBJECT_GET_CLASS(sPAPRIOMMUMemoryRegionClass, obj, \
>> +                         TYPE_SPAPR_IOMMU_MEMORY_REGION)
>> +#define SPAPR_IOMMU_MEMORY_REGION_CLASS(klass) \
>> +        OBJECT_CLASS_CHECK(sPAPRIOMMUMemoryRegionClass, klass, \
>> +                           TYPE_SPAPR_IOMMU_MEMORY_REGION)
>>  
>>  struct sPAPRTCETable {
>>      DeviceState parent;
>> @@ -618,6 +625,14 @@ struct sPAPRTCETable {
>>      QLIST_ENTRY(sPAPRTCETable) list;
>>  };
>>  
>> +struct sPAPRIOMMUMemoryRegionClass {
>> +    /* private */
>> +    IOMMUMemoryRegionClass parent_class;
>> +
>> +    /* public */
>> +    int (*get_fd)(IOMMUMemoryRegion *iommu_mr);
>> +};
>> +
>>  sPAPRTCETable *spapr_tce_find_by_liobn(target_ulong liobn);
> 
> To make sure I'm understanding correctly: the MR subclass here is
> representing a guest-side property, yes?  It means that on the guest
> side the IOMMU mappings are managed by the PAPR {GET,PUT}_TCE
> interface.

I do not understand the question, sorry. MR is a QEMU thing, only QEMU
devices use these MRs as MRs.


>>  struct sPAPREventLogEntry {
>> diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
>> index f3a2ac9fee..d245d3cecc 100644
>> --- a/include/hw/vfio/vfio-common.h
>> +++ b/include/hw/vfio/vfio-common.h
>> @@ -177,6 +177,8 @@ extern const MemoryListener vfio_prereg_listener;
>>  int vfio_spapr_create_window(VFIOContainer *container,
>>                               MemoryRegionSection *section,
>>                               hwaddr *pgsize);
>> +int vfio_spapr_notify_kvm(int vfio_kvm_device_fd, int groupfd,
>> +                          IOMMUMemoryRegion *iommumr);
>>  int vfio_spapr_remove_window(VFIOContainer *container,
>>                               hwaddr offset_within_address_space);
>>  
>> diff --git a/hw/ppc/spapr_iommu.c b/hw/ppc/spapr_iommu.c
>> index 307dc3021e..82fca61a75 100644
>> --- a/hw/ppc/spapr_iommu.c
>> +++ b/hw/ppc/spapr_iommu.c
>> @@ -171,6 +171,13 @@ static void 
>> spapr_tce_notify_flag_changed(IOMMUMemoryRegion *iommu,
>>      }
>>  }
>>  
>> +static int spapr_tce_get_fd(IOMMUMemoryRegion *iommu_mr)
>> +{
>> +    sPAPRTCETable *tcet = container_of(iommu_mr, sPAPRTCETable, iommu);
>> +
>> +    return tcet->fd;
> 
> Does this have a well defined value if there's no KVM?


It is -1 in TCG, any other value is undefined.


> 
>> +}
>> +
>>  static int spapr_tce_table_post_load(void *opaque, int version_id)
>>  {
>>      sPAPRTCETable *tcet = SPAPR_TCE_TABLE(opaque);
>> @@ -631,16 +638,19 @@ static TypeInfo spapr_tce_table_info = {
>>  static void spapr_iommu_memory_region_class_init(ObjectClass *klass, void 
>> *data)
>>  {
>>      IOMMUMemoryRegionClass *imrc = IOMMU_MEMORY_REGION_CLASS(klass);
>> +    sPAPRIOMMUMemoryRegionClass *simrc = 
>> SPAPR_IOMMU_MEMORY_REGION_CLASS(klass);
>>  
>>      imrc->translate = spapr_tce_translate_iommu;
>>      imrc->get_min_page_size = spapr_tce_get_min_page_size;
>>      imrc->notify_flag_changed = spapr_tce_notify_flag_changed;
>> +    simrc->get_fd = spapr_tce_get_fd;
>>  }
>>  
>>  static const TypeInfo spapr_iommu_memory_region_info = {
>>      .parent = TYPE_IOMMU_MEMORY_REGION,
>>      .name = TYPE_SPAPR_IOMMU_MEMORY_REGION,
>>      .class_init = spapr_iommu_memory_region_class_init,
>> +    .class_size = sizeof(sPAPRIOMMUMemoryRegionClass),
>>  };
>>  
>>  static void register_types(void)
>> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
>> index 7b2924c0ef..92f1f88ae8 100644
>> --- a/hw/vfio/common.c
>> +++ b/hw/vfio/common.c
>> @@ -454,6 +454,16 @@ static void vfio_listener_region_add(MemoryListener 
>> *listener,
>>              goto fail;
>>          }
>>  
>> +#ifdef CONFIG_KVM
>> +        if (kvm_enabled()) {
>> +            VFIOGroup *group;
>> +
>> +            QLIST_FOREACH(group, &container->group_list, container_next) {
>> +                vfio_spapr_notify_kvm(vfio_kvm_device_fd, group->fd,
>> +                                      IOMMU_MEMORY_REGION(section->mr));
>> +            }
>> +        }
> 
> So, here you're informing the region of the groups when the region is
> mapped in.  But don't you similarly need to notify if a group is added
> to an existing address space? 

It is either in VFIO for ages (forever? in vfio_connect_container()), or I
did not understand the question...


> And won't you also need notifications
> of groups/regions being removed?

Same comment. vfio_disconnect_container()?


> 
>> +#endif
>>          vfio_host_win_add(container, section->offset_within_address_space,
>>                            section->offset_within_address_space +
>>                            int128_get64(section->size) - 1, pgsize);
>> diff --git a/hw/vfio/spapr.c b/hw/vfio/spapr.c
>> index 32fd6a9b54..2b9af75c03 100644
>> --- a/hw/vfio/spapr.c
>> +++ b/hw/vfio/spapr.c
>> @@ -15,8 +15,12 @@
>>  
>>  #include "hw/vfio/vfio-common.h"
>>  #include "hw/hw.h"
>> +#include "hw/ppc/spapr.h"
>>  #include "qemu/error-report.h"
>>  #include "trace.h"
>> +#ifdef CONFIG_KVM
>> +#include "linux/kvm.h"
>> +#endif
>>  
>>  static bool vfio_prereg_listener_skipped_section(MemoryRegionSection 
>> *section)
>>  {
>> @@ -188,6 +192,41 @@ int vfio_spapr_create_window(VFIOContainer *container,
>>      return 0;
>>  }
>>  
>> +int vfio_spapr_notify_kvm(int vfio_kvm_device_fd, int groupfd,
>> +                          IOMMUMemoryRegion *iommu_mr)
>> +{
>> +#ifdef CONFIG_KVM
>> +    struct kvm_vfio_spapr_tce param = {
>> +        .groupfd = groupfd,
>> +    };
>> +    struct kvm_device_attr attr = {
>> +        .group = KVM_DEV_VFIO_GROUP,
>> +        .attr = KVM_DEV_VFIO_GROUP_SET_SPAPR_TCE,
>> +        .addr = (uint64_t)(unsigned long)&param,
>> +    };
>> +    IOMMUMemoryRegion *spapr_iommu_mr = SPAPR_IOMMU_MEMORY_REGION(iommu_mr);
> 
> This will assert if you have a non-spapr guest IOMMU on a ppc host
> (e.g. emulating an x86 with VT-d under TCG).


Sure but this should not execute when TCG, hence "_kvm" in
"vfio_spapr_notify_kvm".


> 
>> +    sPAPRIOMMUMemoryRegionClass *simrc =
>> +            SPAPR_IOMMU_MEMORY_REGION_GET_CLASS(spapr_iommu_mr);
>> +
>> +    if (!simrc->get_fd) {
>> +        error_report("vfio: No get_fd defined for IOMMU MR");
>> +        return -EFAULT;
>> +    }
>> +
>> +    param.tablefd = simrc->get_fd(spapr_iommu_mr);
>> +
>> +    if (param.tablefd != -1) {
>> +        if (ioctl(vfio_kvm_device_fd, KVM_SET_DEVICE_ATTR, &attr)) {
>> +            error_report("vfio: failed to setup fd %d for a group with fd 
>> %d: %s",
>> +                         param.tablefd, param.groupfd, strerror(errno));
>> +            return -errno;
>> +        }
>> +    }
>> +    trace_vfio_spapr_notify_kvm(groupfd, param.tablefd);
>> +#endif
>> +    return 0;
>> +}
>> +
>>  int vfio_spapr_remove_window(VFIOContainer *container,
>>                               hwaddr offset_within_address_space)
>>  {
>> diff --git a/hw/vfio/trace-events b/hw/vfio/trace-events
>> index 2561c6d31a..084a92f7c2 100644
>> --- a/hw/vfio/trace-events
>> +++ b/hw/vfio/trace-events
>> @@ -123,3 +123,4 @@ vfio_prereg_register(uint64_t va, uint64_t size, int 
>> ret) "va=%"PRIx64" size=%"P
>>  vfio_prereg_unregister(uint64_t va, uint64_t size, int ret) "va=%"PRIx64" 
>> size=%"PRIx64" ret=%d"
>>  vfio_spapr_create_window(int ps, uint64_t ws, uint64_t off) "pageshift=0x%x 
>> winsize=0x%"PRIx64" offset=0x%"PRIx64
>>  vfio_spapr_remove_window(uint64_t off) "offset=%"PRIx64
>> +vfio_spapr_notify_kvm(int groupfd, int tablefd) "Attached groupfd %d to 
>> liobn fd %d"
> 


-- 
Alexey

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