Re: [Qemu-devel] [PATCH qemu v16 18/19] vfio/spapr: Create DMA window dynamically (SPAPR IOMMU v2)

[Alexey Kardashevskiy]

On 17/05/16 06:20, Alex Williamson wrote:
> On Mon, 16 May 2016 14:52:41 +1000
> Alexey Kardashevskiy <address@hidden> wrote:
> 
>> On 05/14/2016 08:26 AM, Alex Williamson wrote:
>>> On Wed,  4 May 2016 16:52:30 +1000
>>> Alexey Kardashevskiy <address@hidden> wrote:
>>>  
>>>> New VFIO_SPAPR_TCE_v2_IOMMU type supports dynamic DMA window management.
>>>> This adds ability to VFIO common code to dynamically allocate/remove
>>>> DMA windows in the host kernel when new VFIO container is added/removed.
>>>>
>>>> This adds VFIO_IOMMU_SPAPR_TCE_CREATE ioctl to vfio_listener_region_add
>>>> and adds just created IOMMU into the host IOMMU list; the opposite
>>>> action is taken in vfio_listener_region_del.
>>>>
>>>> When creating a new window, this uses heuristic to decide on the TCE table
>>>> levels number.
>>>>
>>>> This should cause no guest visible change in behavior.
>>>>
>>>> Signed-off-by: Alexey Kardashevskiy <address@hidden>
>>>> ---
>>>> Changes:
>>>> v16:
>>>> * used memory_region_iommu_get_page_sizes() in vfio_listener_region_add()
>>>> * enforced no intersections between windows
>>>>
>>>> v14:
>>>> * new to the series
>>>> ---
>>>>  hw/vfio/common.c | 133 
>>>> ++++++++++++++++++++++++++++++++++++++++++++++++++-----
>>>>  trace-events     |   2 +
>>>>  2 files changed, 125 insertions(+), 10 deletions(-)
>>>>
>>>> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
>>>> index 03daf88..bd2dee8 100644
>>>> --- a/hw/vfio/common.c
>>>> +++ b/hw/vfio/common.c
>>>> @@ -240,6 +240,18 @@ static int vfio_dma_map(VFIOContainer *container, 
>>>> hwaddr iova,
>>>>      return -errno;
>>>>  }
>>>>
>>>> +static bool range_contains(hwaddr start, hwaddr end, hwaddr addr)
>>>> +{
>>>> +    return start <= addr && addr <= end;
>>>> +}  
>>>
>>> a) If you want a "range_foo" function then put it in range.h
>>> b) I suspect there are already range.h functions that can do this.
>>>  
>>>> +
>>>> +static bool vfio_host_win_intersects(VFIOHostDMAWindow *hostwin,
>>>> +                                     hwaddr min_iova, hwaddr max_iova)
>>>> +{
>>>> +    return range_contains(hostwin->min_iova, hostwin->min_iova, min_iova) 
>>>> ||
>>>> +        range_contains(min_iova, max_iova, hostwin->min_iova);
>>>> +}  
>>>
>>> How is this different than ranges_overlap()?  
>>>> +
>>>>  static VFIOHostDMAWindow *vfio_host_win_lookup(VFIOContainer *container,
>>>>                                                 hwaddr min_iova, hwaddr 
>>>> max_iova)
>>>>  {
>>>> @@ -279,6 +291,14 @@ static int vfio_host_win_add(VFIOContainer *container,
>>>>      return 0;
>>>>  }
>>>>
>>>> +static void vfio_host_win_del(VFIOContainer *container, hwaddr min_iova)
>>>> +{
>>>> +    VFIOHostDMAWindow *hostwin = vfio_host_win_lookup(container, 
>>>> min_iova, 1);
>>>> +
>>>> +    g_assert(hostwin);  
>>>
>>> Handle the error please.  
>>
>> Will this be enough?
>>
>>      if (!hostwin) {
>>          error_report("%s: Cannot delete missing window at %"HWADDR_PRIx,
>>                       __func__, min_iova);
>>          return;
>>      }
> 
> Better.  I was really thinking to return error to the caller, but if
> the caller has no return path, perhaps this is as good as we can do.
> Expect that I will push back on any assert() calls added to vfio.
> 
> 
>>>> +    QLIST_REMOVE(hostwin, hostwin_next);
>>>> +}
>>>> +
>>>>  static bool vfio_listener_skipped_section(MemoryRegionSection *section)
>>>>  {
>>>>      return (!memory_region_is_ram(section->mr) &&
>>>> @@ -392,6 +412,69 @@ static void vfio_listener_region_add(MemoryListener 
>>>> *listener,
>>>>      }
>>>>      end = int128_get64(int128_sub(llend, int128_one()));
>>>>
>>>> +    if (container->iommu_type == VFIO_SPAPR_TCE_v2_IOMMU) {
>>>> +        VFIOHostDMAWindow *hostwin;
>>>> +        unsigned pagesizes = 
>>>> memory_region_iommu_get_page_sizes(section->mr);
>>>> +        unsigned pagesize = (hwaddr)1 << ctz64(pagesizes);
>>>> +        unsigned entries, pages;
>>>> +        struct vfio_iommu_spapr_tce_create create = { .argsz = 
>>>> sizeof(create) };
>>>> +
>>>> +        trace_vfio_listener_region_add_iommu(iova, end);
>>>> +        /*
>>>> +         * FIXME: For VFIO iommu types which have KVM acceleration to
>>>> +         * avoid bouncing all map/unmaps through qemu this way, this
>>>> +         * would be the right place to wire that up (tell the KVM
>>>> +         * device emulation the VFIO iommu handles to use).
>>>> +         */
>>>> +        create.window_size = int128_get64(section->size);
>>>> +        create.page_shift = ctz64(pagesize);
>>>> +        /*
>>>> +         * SPAPR host supports multilevel TCE tables, there is some
>>>> +         * heuristic to decide how many levels we want for our table:
>>>> +         * 0..64 = 1; 65..4096 = 2; 4097..262144 = 3; 262145.. = 4
>>>> +         */
>>>> +        entries = create.window_size >> create.page_shift;
>>>> +        pages = MAX((entries * sizeof(uint64_t)) / getpagesize(), 1);
>>>> +        pages = MAX(pow2ceil(pages) - 1, 1); /* Round up */
>>>> +        create.levels = ctz64(pages) / 6 + 1;
>>>> +
>>>> +        /* For now intersections are not allowed, we may relax this later 
>>>> */
>>>> +        QLIST_FOREACH(hostwin, &container->hostwin_list, hostwin_next) {
>>>> +            if (vfio_host_win_intersects(hostwin,
>>>> +                    section->offset_within_address_space,
>>>> +                    section->offset_within_address_space +
>>>> +                    create.window_size - 1)) {
>>>> +                goto fail;
>>>> +            }
>>>> +        }
>>>> +
>>>> +        ret = ioctl(container->fd, VFIO_IOMMU_SPAPR_TCE_CREATE, &create);
>>>> +        if (ret) {
>>>> +            error_report("Failed to create a window, ret = %d (%m)", ret);
>>>> +            goto fail;
>>>> +        }
>>>> +
>>>> +        if (create.start_addr != section->offset_within_address_space) {
>>>> +            struct vfio_iommu_spapr_tce_remove remove = {
>>>> +                .argsz = sizeof(remove),
>>>> +                .start_addr = create.start_addr
>>>> +            };
>>>> +            error_report("Host doesn't support DMA window at 
>>>> %"HWADDR_PRIx", must be %"PRIx64,
>>>> +                         section->offset_within_address_space,
>>>> +                         create.start_addr);
>>>> +            ioctl(container->fd, VFIO_IOMMU_SPAPR_TCE_REMOVE, &remove);
>>>> +            ret = -EINVAL;
>>>> +            goto fail;
>>>> +        }
>>>> +        trace_vfio_spapr_create_window(create.page_shift,
>>>> +                                       create.window_size,
>>>> +                                       create.start_addr);
>>>> +
>>>> +        vfio_host_win_add(container, create.start_addr,
>>>> +                          create.start_addr + create.window_size - 1,
>>>> +                          1ULL << create.page_shift);
>>>> +    }  
>>>
>>> This is a function on its own, split it out and why not stop pretending
>>> prereg is some sort of generic interface and let's just make a spapr
>>> support file.  
>>
>>
>> Yet another new file - spapr.c, or rename prereg.c to spapr.c and add this 
>> stuff there?
> 
> prereg.c is already spapr specific, so I'd rename it and potentially
> add this to it.


It would help if you two decided what I should do about prereg.c vs.
spapr.c - merge or keep 2 files. Thanks.




-- 
Alexey