On 23/11/16 12:35, David Gibson wrote:
> On Tue, Nov 22, 2016 at 06:29:39PM +1100, Alexey Kardashevskiy wrote:
>> On 22/11/16 13:50, David Gibson wrote:
>>> On Fri, Nov 11, 2016 at 11:32:15PM +1100, Alexey Kardashevskiy wrote:
>>>> As mentioned in the previous patch, we are going to allow the userspace
>>>> to configure container in one memory context and pass container fd to
>>>> another so we are postponing memory allocations accounted against
>>>> the locked memory limit. The previous patch took care of it_userspace.
>>>>
>>>> At the moment we create the default DMA window when the first group is
>>>> attached to a container; this is done for the userspace which is not
>>>> DDW-aware but familiar with the SPAPR TCE IOMMU v2 in the part of memory
>>>> pre-registration - such client expects the default DMA window to exist.
>>>>
>>>> This postpones the default DMA window allocation till first map/unmap
>>>> request happens.
>>>>
>>>> Signed-off-by: Alexey Kardashevskiy <aik@xxxxxxxxx>
>>>> ---
>>>> drivers/vfio/vfio_iommu_spapr_tce.c | 98 ++++++++++++++++++-------------------
>>>> 1 file changed, 47 insertions(+), 51 deletions(-)
>>>>
>>>> diff --git a/drivers/vfio/vfio_iommu_spapr_tce.c b/drivers/vfio/vfio_iommu_spapr_tce.c
>>>> index 442baac..1c02498 100644
>>>> --- a/drivers/vfio/vfio_iommu_spapr_tce.c
>>>> +++ b/drivers/vfio/vfio_iommu_spapr_tce.c
>>>> @@ -97,6 +97,7 @@ struct tce_container {
>>>> struct mutex lock;
>>>> bool enabled;
>>>> bool v2;
>>>> + bool def_window_pending;
>>>> unsigned long locked_pages;
>>>> struct iommu_table *tables[IOMMU_TABLE_GROUP_MAX_TABLES];
>>>> struct list_head group_list;
>>>> @@ -594,15 +595,6 @@ static long tce_iommu_create_table(struct tce_container *container,
>>>> WARN_ON(!ret && !(*ptbl)->it_ops->free);
>>>> WARN_ON(!ret && ((*ptbl)->it_allocated_size != table_size));
>>>>
>>>> - if (!ret && container->v2) {
>>>> - ret = tce_iommu_userspace_view_alloc(*ptbl);
>>>> - if (ret)
>>>> - (*ptbl)->it_ops->free(*ptbl);
>>>> - }
>>>
>>> Does this stuff for the user view belong in the previous patch?
>>
>> Yes it does, my mistake, will fix.
>>
>>
>>>
>>>> -
>>>> - if (ret)
>>>> - decrement_locked_vm(table_size >> PAGE_SHIFT);
>>>> -
>>>> return ret;
>>>> }
>>>>
>>>> @@ -719,6 +711,29 @@ static long tce_iommu_remove_window(struct tce_container *container,
>>>> return 0;
>>>> }
>>>>
>>>> +static long tce_iommu_create_default_window(struct tce_container *container)
>>>> +{
>>>> + long ret;
>>>> + __u64 start_addr = 0;
>>>> + struct tce_iommu_group *tcegrp;
>>>> + struct iommu_table_group *table_group;
>>>> +
>>>> + if (!tce_groups_attached(container))
>>>> + return -ENODEV;
>>>> +
>>>> + tcegrp = list_first_entry(&container->group_list,
>>>> + struct tce_iommu_group, next);
>>>> + table_group = iommu_group_get_iommudata(tcegrp->grp);
>>>> + if (!table_group)
>>>> + return -ENODEV;
>>>> +
>>>> + ret = tce_iommu_create_window(container, IOMMU_PAGE_SHIFT_4K,
>>>> + table_group->tce32_size, 1, &start_addr);
>>>> + WARN_ON_ONCE(!ret && start_addr);
>>>> +
>>>> + return ret;
>>>> +}
>>>> +
>>>> static long tce_iommu_ioctl(void *iommu_data,
>>>> unsigned int cmd, unsigned long arg)
>>>> {
>>>> @@ -809,6 +824,13 @@ static long tce_iommu_ioctl(void *iommu_data,
>>>> VFIO_DMA_MAP_FLAG_WRITE))
>>>> return -EINVAL;
>>>>
>>>> + if (container->def_window_pending) {
>>>> + ret = tce_iommu_create_default_window(container);
>>>> + if (ret)
>>>> + return ret;
>>>> + container->def_window_pending = false;
>>>
>>> Would it make sense to clear (and maybe test) def_window_pending
>>> within create_default_window()?
>>
>> Dunno, matter of taste I suppose. I'll move it there.
>>
>>
>>>
>>>> + }
>>>> +
>>>> num = tce_iommu_find_table(container, param.iova, &tbl);
>>>> if (num < 0)
>>>> return -ENXIO;
>>>> @@ -872,6 +894,13 @@ static long tce_iommu_ioctl(void *iommu_data,
>>>> if (param.flags)
>>>> return -EINVAL;
>>>>
>>>> + if (container->def_window_pending) {
>>>> + ret = tce_iommu_create_default_window(container);
>>>> + if (ret)
>>>> + return ret;
>>>> + container->def_window_pending = false;
>>>> + }
>>>> +
>>>> num = tce_iommu_find_table(container, param.iova, &tbl);
>>>> if (num < 0)
>>>> return -ENXIO;
>>>> @@ -998,6 +1027,8 @@ static long tce_iommu_ioctl(void *iommu_data,
>>>>
>>>> mutex_lock(&container->lock);
>>>>
>>>> + container->def_window_pending = false;
>>>
>>> Uh.. why is it cleared here, without calling
>>> tce_iommu_create_default_window() AFAICT?
>>
>>
>> It is a branch which creates new window, if we do not have a default
>> window, then it will be created as the result of this ioctl(), if there is
>> a default window, then the flag should be false already.
>
> Um.. it will create *a* window, but not necessarily the default one.
> Consider this scenario:
>
> 1. Container is opened
> 2. A group is attached
> 3. Userspace, expecting the default window to be in place, creates a
> second window
> 4. Mapping starts
>
> Won't the above code mean that we create what userspace expected to be
> the second window as the first window replacing the default one
> instead?
Uff. Yes, this is correct.
This is a bug in my initial design - I should not have created a "default"
window in the first place - it does not make sense at this level; and the
userspace (i.e. QEMU) removes all windows on reset anyway.
The only way QEMU will use this default window is when it is at 318f67ce1
"vfio: spapr: Add DMA memory preregistering (SPAPR IOMMU v2)" - memory
preregistration is there, but ddw is not yet but it is 2 patches later
where vfio_connect_container() unconditionally removes the default window.
Which is unlikely scenario.
Taking into account small number of DDW users (basically - QEMU v2.7.0),
does it still make sense to keep this default window code? The only
immediate problem I see here is QEMU will receive error from
vfio_spapr_remove_window() in vfio_connect_container() as there will be no
default window but I could workaround this.
>
>>
>>
>>
>>
>>>
>>>> ret = tce_iommu_create_window(container, create.page_shift,
>>>> create.window_size, create.levels,
>>>> &create.start_addr);
>>>> @@ -1030,6 +1061,12 @@ static long tce_iommu_ioctl(void *iommu_data,
>>>> if (remove.flags)
>>>> return -EINVAL;
>>>>
>>>> + if (container->def_window_pending && !remove.start_addr) {
>>>> + container->def_window_pending = false;
>>>> + return 0;
>>>> + }
>>>> + container->def_window_pending = false;
>>>> +
>>>> mutex_lock(&container->lock);
>>>>
>>>> ret = tce_iommu_remove_window(container, remove.start_addr);
>>>> @@ -1109,9 +1146,6 @@ static void tce_iommu_release_ownership_ddw(struct tce_container *container,
>>>> static long tce_iommu_take_ownership_ddw(struct tce_container *container,
>>>> struct iommu_table_group *table_group)
>>>> {
>>>> - long i, ret = 0;
>>>> - struct iommu_table *tbl = NULL;
>>>> -
>>>> if (!table_group->ops->create_table || !table_group->ops->set_window ||
>>>> !table_group->ops->release_ownership) {
>>>> WARN_ON_ONCE(1);
>>>> @@ -1120,47 +1154,9 @@ static long tce_iommu_take_ownership_ddw(struct tce_container *container,
>>>>
>>>> table_group->ops->take_ownership(table_group);
>>>>
>>>> - /*
>>>> - * If it the first group attached, check if there is
>>>> - * a default DMA window and create one if none as
>>>> - * the userspace expects it to exist.
>>>> - */
>>>> - if (!tce_groups_attached(container) && !container->tables[0]) {
>>>> - ret = tce_iommu_create_table(container,
>>>> - table_group,
>>>> - 0, /* window number */
>>>> - IOMMU_PAGE_SHIFT_4K,
>>>> - table_group->tce32_size,
>>>> - 1, /* default levels */
>>>> - &tbl);
>>>> - if (ret)
>>>> - goto release_exit;
>>>> - else
>>>> - container->tables[0] = tbl;
>>>> - }
>>>> -
>>>> - /* Set all windows to the new group */
>>>> - for (i = 0; i < IOMMU_TABLE_GROUP_MAX_TABLES; ++i) {
>>>> - tbl = container->tables[i];
>>>> -
>>>> - if (!tbl)
>>>> - continue;
>>>> -
>>>> - /* Set the default window to a new group */
>>>> - ret = table_group->ops->set_window(table_group, i, tbl);
>>>
>>> Uh... nothing in the new code seems to replace these set_window (and
>>> unset_window) calls. What's up with that?
>>
>>
>> tce_iommu_create_table() + set_window() is replaced with
>> tce_iommu_create_default_window() which calls tce_iommu_create_window()
>> which calls tce_iommu_create_table() + set_window().
>>
>> I'll split this patch into 2 patches, one with the change I just explained
>> and one to postpone the default window creation.
>
> Ah, right, I see.
>
>
>>
>>
>>>
>>>> - if (ret)
>>>> - goto release_exit;
>>>> - }
>>>> + container->def_window_pending = true;
>>>>
>>>> return 0;
>>>> -
>>>> -release_exit:
>>>> - for (i = 0; i < IOMMU_TABLE_GROUP_MAX_TABLES; ++i)
>>>> - table_group->ops->unset_window(table_group, i);
>>>> -
>>>> - table_group->ops->release_ownership(table_group);
>>>> -
>>>> - return ret;
>>>> }
>>>>
>>>> static int tce_iommu_attach_group(void *iommu_data,
>>>
>>
>>
>
>
>
>
--
Alexey
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