Re: [Qemu-ppc] [PATCH qemu v6 07/15] vfio: spapr: Add SPAPR IOMMU v2 support (DMA memory preregistering)

[David Gibson]

On Sat, Apr 11, 2015 at 01:24:36AM +1000, Alexey Kardashevskiy wrote:
> This makes use of the new "memory registering" feature. The idea is
> to provide the userspace ability to notify the host kernel about pages
> which are going to be used for DMA. Having this information, the host
> kernel can pin them all once per user process, do locked pages
> accounting (once) and not spent time on doing that in real time with
> possible failures which cannot be handled nicely in some cases.
> 
> This adds a guest RAM memory listener which notifies a VFIO container
> about memory which needs to be pinned/unpinned. VFIO MMIO regions
> (i.e. "skip dump" regions) are skipped.
> 
> The feature is only enabled for SPAPR IOMMU v2. The host kernel changes
> are required. Since v2 does not need/support VFIO_IOMMU_ENABLE, this does
> not call it when v2 is detected and enabled.
> 
> This does not change the guest visible interface.
> 
> Signed-off-by: Alexey Kardashevskiy <address@hidden>

Reviewed-by: David Gibson <address@hidden>

Albeit with some nits described below.

> ---
> Changes:
> v6:
> * fixed commit log (s/guest/userspace/), added note about no guest visible
> change
> * fixed error checking if ram registration failed
> * added alignment check for section->offset_within_region
> 
> v5:
> * simplified the patch
> * added trace points
> * added round_up() for the size
> * SPAPR IOMMU v2 used
> ---
>  hw/vfio/common.c              | 26 +++++++++----
>  hw/vfio/spapr.c               | 88 
> ++++++++++++++++++++++++++++++++++++++++++-
>  include/hw/vfio/vfio-common.h |  5 ++-
>  trace-events                  |  1 +
>  4 files changed, 109 insertions(+), 11 deletions(-)
> 
> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> index 369e564..9e3e0b0 100644
> --- a/hw/vfio/common.c
> +++ b/hw/vfio/common.c
> @@ -577,14 +577,18 @@ static int vfio_connect_container(VFIOGroup *group, 
> AddressSpace *as)
>  
>          container->iommu_data.type1.initialized = true;
>  
> -    } else if (ioctl(fd, VFIO_CHECK_EXTENSION, VFIO_SPAPR_TCE_IOMMU)) {
> +    } else if (ioctl(fd, VFIO_CHECK_EXTENSION, VFIO_SPAPR_TCE_IOMMU) ||
> +               ioctl(fd, VFIO_CHECK_EXTENSION, VFIO_SPAPR_TCE_v2_IOMMU)) {
> +        bool v2 = !!ioctl(fd, VFIO_CHECK_EXTENSION, VFIO_SPAPR_TCE_v2_IOMMU);
> +
>          ret = ioctl(group->fd, VFIO_GROUP_SET_CONTAINER, &fd);
>          if (ret) {
>              error_report("vfio: failed to set group container: %m");
>              ret = -errno;
>              goto free_container_exit;
>          }
> -        ret = ioctl(fd, VFIO_SET_IOMMU, VFIO_SPAPR_TCE_IOMMU);
> +        ret = ioctl(fd, VFIO_SET_IOMMU,
> +                v2 ? VFIO_SPAPR_TCE_v2_IOMMU : VFIO_SPAPR_TCE_IOMMU);
>          if (ret) {
>              error_report("vfio: failed to set iommu for container: %m");
>              ret = -errno;
> @@ -596,14 +600,20 @@ static int vfio_connect_container(VFIOGroup *group, 
> AddressSpace *as)
>           * when container fd is closed so we do not call it explicitly
>           * in this file.
>           */
> -        ret = ioctl(fd, VFIO_IOMMU_ENABLE);
> -        if (ret) {
> -            error_report("vfio: failed to enable container: %m");
> -            ret = -errno;
> -            goto free_container_exit;
> +        if (!v2) {
> +            ret = ioctl(fd, VFIO_IOMMU_ENABLE);
> +            if (ret) {
> +                error_report("vfio: failed to enable container: %m");
> +                ret = -errno;
> +                goto free_container_exit;
> +            }
>          }
>  
> -        spapr_memory_listener_register(container);
> +        ret = spapr_memory_listener_register(container, v2 ? 2 : 1);
> +        if (ret) {
> +            error_report("vfio: RAM memory listener initialization failed 
> for container");
> +            goto listener_release_exit;
> +        }
>  
>      } else {
>          error_report("vfio: No available IOMMU models");
> diff --git a/hw/vfio/spapr.c b/hw/vfio/spapr.c
> index 5f79194..31353f1 100644
> --- a/hw/vfio/spapr.c
> +++ b/hw/vfio/spapr.c
> @@ -17,6 +17,9 @@
>   *  along with this program; if not, see <http://www.gnu.org/licenses/>.
>   */
>  
> +#include <sys/ioctl.h>
> +#include <linux/vfio.h>
> +
>  #include "hw/vfio/vfio-common.h"
>  #include "qemu/error-report.h"
>  #include "trace.h"
> @@ -211,16 +214,97 @@ static const MemoryListener vfio_spapr_memory_listener 
> = {
>      .region_del = vfio_spapr_listener_region_del,
>  };
>  
> +static void vfio_ram_do_region(VFIOContainer *container,
> +                              MemoryRegionSection *section, unsigned long 
> req)
> +{
> +    int ret;
> +    struct vfio_iommu_spapr_register_memory reg = { .argsz = sizeof(reg) };
> +
> +    if (!memory_region_is_ram(section->mr) ||
> +        memory_region_is_skip_dump(section->mr)) {
> +        return;
> +    }
> +
> +    if (unlikely((section->offset_within_region & (getpagesize() - 1)))) {
> +        error_report("%s received unaligned region", __func__);
> +        return;
> +    }
> +
> +    reg.vaddr = (__u64) memory_region_get_ram_ptr(section->mr) +
> +        section->offset_within_region;
> +    reg.size = ROUND_UP(int128_get64(section->size), TARGET_PAGE_SIZE);
> +
> +    ret = ioctl(container->fd, req, &reg);
> +    trace_vfio_ram_register(_IOC_NR(req) - VFIO_BASE, reg.vaddr, reg.size,
> +            ret ? -errno : 0);
> +    if (!ret) {
> +        return;
> +    }
> +
> +    /*
> +     * On the initfn path, store the first error in the container so we
> +     * can gracefully fail.  Runtime, there's not much we can do other
> +     * than throw a hardware error.
> +     */
> +    if (!container->iommu_data.spapr.ram_reg_initialized) {
> +        if (!container->iommu_data.spapr.ram_reg_error) {
> +            container->iommu_data.spapr.ram_reg_error = -errno;
> +        }
> +    } else {
> +        hw_error("vfio: RAM registering failed, unable to continue");
> +    }
> +}
> +
> +static void vfio_spapr_ram_listener_region_add(MemoryListener *listener,
> +                                               MemoryRegionSection *section)
> +{
> +    VFIOContainer *container = container_of(listener, VFIOContainer,
> +                                            iommu_data.spapr.ramlistener);
> +    memory_region_ref(section->mr);
> +    vfio_ram_do_region(container, section, VFIO_IOMMU_SPAPR_REGISTER_MEMORY);
> +}
> +
> +static void vfio_spapr_ram_listener_region_del(MemoryListener *listener,
> +                                               MemoryRegionSection *section)
> +{
> +    VFIOContainer *container = container_of(listener, VFIOContainer,
> +                                            iommu_data.spapr.ramlistener);
> +    memory_region_unref(section->mr);

You're probably safe because of the QBL, but it would be more
obviously correct if you did the ioctl unregister before unreferencing
the MR.

> +    vfio_ram_do_region(container, section, 
> VFIO_IOMMU_SPAPR_UNREGISTER_MEMORY);
> +}
> +
> +static const MemoryListener vfio_spapr_ram_memory_listener = {
> +    .region_add = vfio_spapr_ram_listener_region_add,
> +    .region_del = vfio_spapr_ram_listener_region_del,
> +};
> +
>  static void vfio_spapr_listener_release(VFIOContainer *container)
>  {
>      memory_listener_unregister(&container->iommu_data.spapr.listener);
>  }
>  
> -void spapr_memory_listener_register(VFIOContainer *container)
> +static void vfio_spapr_listener_release_v2(VFIOContainer *container)
> +{
> +    memory_listener_unregister(&container->iommu_data.spapr.listener);
> +    vfio_spapr_listener_release(container);
> +}
> +
> +int spapr_memory_listener_register(VFIOContainer *container, int ver)
>  {
>      container->iommu_data.spapr.listener = vfio_spapr_memory_listener;
>      container->iommu_data.release = vfio_spapr_listener_release;
> -
>      memory_listener_register(&container->iommu_data.spapr.listener,
>                               container->space->as);
> +    if (ver < 2) {
> +        return 0;
> +    }

I wonder if it would make sense to store the IOMMU type value into the
VFIOContainer (from non-arch specific code).  It would avoid the
ad-hoc passing of version here and also allow for some sanity checks.

> +
> +    container->iommu_data.spapr.ramlistener = vfio_spapr_ram_memory_listener;
> +    container->iommu_data.release = vfio_spapr_listener_release_v2;
> +    memory_listener_register(&container->iommu_data.spapr.ramlistener,
> +                             &address_space_memory);
> +
> +    container->iommu_data.spapr.ram_reg_initialized = true;
> +
> +    return container->iommu_data.spapr.ram_reg_error;
>  }
> diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
> index d0b831c..b5ef446 100644
> --- a/include/hw/vfio/vfio-common.h
> +++ b/include/hw/vfio/vfio-common.h
> @@ -71,6 +71,9 @@ typedef struct VFIOType1 {
>  
>  typedef struct VFIOSPAPR {
>      MemoryListener listener;
> +    MemoryListener ramlistener;

The names "listener" and "ramlistener" don't exactly give a clear hint
as to what the difference between them is.  Maybe "register_listener"
for the new one since its purpose is to register dma memory.  I forget
what the purpose of the old one is, and so what a better name for it
might be.

> +    int ram_reg_error;
> +    bool ram_reg_initialized;
>  } VFIOSPAPR;
>  
>  typedef struct VFIOContainer {
> @@ -156,6 +159,6 @@ extern int vfio_dma_unmap(VFIOContainer *container,
>                            hwaddr iova, ram_addr_t size);
>  bool vfio_listener_skipped_section(MemoryRegionSection *section);
>  
> -extern void spapr_memory_listener_register(VFIOContainer *container);
> +extern int spapr_memory_listener_register(VFIOContainer *container, int ver);
>  
>  #endif /* !HW_VFIO_VFIO_COMMON_H */
> diff --git a/trace-events b/trace-events
> index 1231ba4..2739140 100644
> --- a/trace-events
> +++ b/trace-events
> @@ -1563,6 +1563,7 @@ vfio_disconnect_container(int fd) "close 
> container->fd=%d"
>  vfio_put_group(int fd) "close group->fd=%d"
>  vfio_get_device(const char * name, unsigned int flags, unsigned int 
> num_regions, unsigned int num_irqs) "Device %s flags: %u, regions: %u, irqs: 
> %u"
>  vfio_put_base_device(int fd) "close vdev->fd=%d"
> +vfio_ram_register(int req, uint64_t va, uint64_t size, int ret) "req=%d 
> va=%"PRIx64" size=%"PRIx64" ret=%d"
>  
>  #hw/acpi/memory_hotplug.c
>  mhp_acpi_invalid_slot_selected(uint32_t slot) "0x%"PRIx32

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

pgpCcZQHPzJUZ.pgp
Description: PGP signature