[Resend,RFC,1/4] VFIO: Set eventfd for IOMMU fault event via new vfio cmd

This patch is to assign an event fd to VFIO IOMMU type1 driver
in order to get notification when IOMMU driver reports fault event.

Signed-off-by: Lan Tianyu <tianyu.lan@intel.com>
---
 hw/vfio/common.c              | 37 +++++++++++++++++++++++++++++++++++++
 include/hw/vfio/vfio-common.h |  3 +++
 linux-headers/linux/vfio.h    | 13 +++++++++++++
 3 files changed, 53 insertions(+)

On Mon, 20 Feb 2017 09:28:04 +0800
Lan Tianyu <tianyu.lan@intel.com> wrote:

> This patch is to assign an event fd to VFIO IOMMU type1 driver
> in order to get notification when IOMMU driver reports fault event.
> 
> Signed-off-by: Lan Tianyu <tianyu.lan@intel.com>
> ---
>  hw/vfio/common.c              | 37 +++++++++++++++++++++++++++++++++++++
>  include/hw/vfio/vfio-common.h |  3 +++
>  linux-headers/linux/vfio.h    | 13 +++++++++++++
>  3 files changed, 53 insertions(+)
> 
> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> index 6b33b9f..628b424 100644
> --- a/hw/vfio/common.c
> +++ b/hw/vfio/common.c
> @@ -33,6 +33,7 @@
>  #include "qemu/error-report.h"
>  #include "qemu/range.h"
>  #include "sysemu/kvm.h"
> +#include "sysemu/sysemu.h"
>  #include "trace.h"
>  #include "qapi/error.h"
>  
> @@ -294,6 +295,34 @@ static bool vfio_listener_skipped_section(MemoryRegionSection *section)
>             section->offset_within_address_space & (1ULL << 63);
>  }
>  
> +static void vfio_iommu_fault(void *opaque)
> +{
> +}
> +
> +static int vfio_set_iommu_fault_notifier(struct VFIOContainer *container)
> +{
> +    struct vfio_iommu_type1_set_fault_eventfd eventfd;
> +    int ret;
> +
> +    ret = event_notifier_init(&container->fault_notifier, 0);
> +    if (ret < 0) {
> +        error_report("vfio: Failed to init notifier for IOMMU fault event");
> +        return ret;
> +    }
> +
> +    eventfd.fd = event_notifier_get_fd(&container->fault_notifier);
> +    eventfd.argsz = sizeof(eventfd);
> +
> +    ret = ioctl(container->fd, VFIO_IOMMU_SET_FAULT_EVENTFD, &eventfd);
> +    if (ret < 0) {
> +        error_report("vfio: Failed to set notifier for IOMMU fault event");
> +        return ret;
> +    }
> +
> +    qemu_set_fd_handler(eventfd.fd, vfio_iommu_fault, NULL, container);
> +    return 0;
> +}
> +
>  /* Called with rcu_read_lock held.  */
>  static bool vfio_get_vaddr(IOMMUTLBEntry *iotlb, void **vaddr,
>                             bool *read_only)
> @@ -1103,6 +1132,14 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as,
>          goto listener_release_exit;
>      }
>  
> +    if (memory_region_is_iommu(container->space->as->root)) {
> +        if (vfio_set_iommu_fault_notifier(container)) {
> +            error_setg_errno(errp, -ret,
> +                "Fail to set IOMMU fault notifier");
> +            goto listener_release_exit;
> +        }
> +    }


Backwards compatibility needs to be supported, we can't invent a
feature and impose it on all users.  We can either opportunistically
enable it and be silent about it when it's not there, or we can add a
feature flag and complain and fail if the user requests the feature and
it's not available or errors.

> +
>      container->initialized = true;
>  
>      QLIST_INIT(&container->group_list);
> diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
> index c582de1..1b594c6 100644
> --- a/include/hw/vfio/vfio-common.h
> +++ b/include/hw/vfio/vfio-common.h
> @@ -26,6 +26,7 @@
>  #include "exec/memory.h"
>  #include "qemu/queue.h"
>  #include "qemu/notify.h"
> +#include "qemu/event_notifier.h"
>  #ifdef CONFIG_LINUX
>  #include <linux/vfio.h>
>  #endif
> @@ -81,6 +82,8 @@ typedef struct VFIOContainer {
>      unsigned iommu_type;
>      int error;
>      bool initialized;
> +    EventNotifier fault_notifier;
> +
>      /*
>       * This assumes the host IOMMU can support only a single
>       * contiguous IOVA window.  We may need to generalize that in
> diff --git a/linux-headers/linux/vfio.h b/linux-headers/linux/vfio.h
> index 759b850..ca890ee 100644
> --- a/linux-headers/linux/vfio.h
> +++ b/linux-headers/linux/vfio.h
> @@ -537,6 +537,19 @@ struct vfio_iommu_type1_dma_unmap {
>  #define VFIO_IOMMU_ENABLE	_IO(VFIO_TYPE, VFIO_BASE + 15)
>  #define VFIO_IOMMU_DISABLE	_IO(VFIO_TYPE, VFIO_BASE + 16)
>  
> +/*
> + * VFIO_IOMMU_SET_FAULT_EVENT_FD	_IO(VFIO_TYPE, VFIO_BASE + 17)
> + * 
> + * Receive eventfd from userspace to notify fault event from IOMMU.
> + */
> +struct vfio_iommu_type1_set_fault_eventfd {
> +	__u32	argsz;
> +	__u32   flags;
> +	__u32	fd;
> +};
> +
> +#define VFIO_IOMMU_SET_FAULT_EVENTFD	_IO(VFIO_TYPE, VFIO_BASE + 17)
> +
>  /* -------- Additional API for SPAPR TCE (Server POWERPC) IOMMU -------- */
>  
>  /*