[PATCH v2 2/3] drm/xe/sriov: Shifting GGTT area post migration
Lis, Tomasz
tomasz.lis at intel.com
Sat Nov 23 02:38:18 UTC 2024
On 16.11.2024 20:29, Michal Wajdeczko wrote:
> On 16.11.2024 03:12, Tomasz Lis wrote:
>> We have only one GGTT for all IOV functions, with each VF having assigned
>> a range of addresses for its use. After migration, a VF can receive a
>> different range of addresses than it had initially.
>>
>> This implements shifting GGTT addresses within drm_mm nodes, so that
>> VMAs stay valid after migration. This will make the driver use new
>> addresses when accessing GGTT from the moment the shifting ends.
>>
>> By taking the ggtt->lock for the period of VMA fixups, this change
>> also adds constaint on that mutex. Any locks used during the recovery
>> cannot ever wait for hardware response - because after migration,
>> the hardware will not do anything until fixups are finished.
>>
>> Signed-off-by: Tomasz Lis<tomasz.lis at intel.com>
>> ---
>> drivers/gpu/drm/xe/xe_gt_sriov_vf.c | 175 ++++++++++++++++++++++++++++
>> drivers/gpu/drm/xe/xe_gt_sriov_vf.h | 1 +
>> drivers/gpu/drm/xe/xe_sriov_vf.c | 15 +++
>> 3 files changed, 191 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/xe/xe_gt_sriov_vf.c b/drivers/gpu/drm/xe/xe_gt_sriov_vf.c
>> index cca5d5732802..ae24c47ed8f8 100644
>> --- a/drivers/gpu/drm/xe/xe_gt_sriov_vf.c
>> +++ b/drivers/gpu/drm/xe/xe_gt_sriov_vf.c
>> @@ -912,6 +912,181 @@ int xe_gt_sriov_vf_query_runtime(struct xe_gt *gt)
>> return err;
>> }
>>
>> +static u64 drm_mm_node_end(struct drm_mm_node *node)
>> +{
>> + return node->start + node->size;
>> +}
>> +
>> +static s64 vf_get_post_migration_ggtt_shift(struct xe_gt *gt)
>> +{
>> + struct xe_gt_sriov_vf_selfconfig *config = >->sriov.vf.self_config;
> I'm wondering whether it would be possible to set/remember any GGTT
> shift when VF was querying it's new config?
The querying happens within post-migration recovery worker, after the
upcoming lock is taken.
So subtracting old from new just after the GuC config query would be doable.
Yeah, will do that.
>> + struct xe_tile *tile = gt_to_tile(gt);
>> + u64 old_base;
>> + s64 ggtt_shift;
>> +
>> + old_base = drm_mm_node_end(&tile->sriov.vf.ggtt_balloon[0]->base);
>> + ggtt_shift = config->ggtt_base - (s64)old_base;
>> +
>> + xe_gt_sriov_info(gt, "GGTT base shifted from %#llx to %#llx\n",
>> + old_base, old_base + ggtt_shift);
>> +
>> + return ggtt_shift;
>> +}
>> +
>> +static void xe_ggtt_mm_shift_nodes(struct xe_ggtt *ggtt, struct drm_mm_node *balloon_beg,
>> + struct drm_mm_node *balloon_fin, s64 shift)
> there is way too much internals that should be just known to the xe_ggtt
> maybe better to move most of this function to xe_ggtt.c ?
Sure, I can move them. Will do.
>> +{
>> + struct drm_mm_node *node, *tmpn;
>> + int err;
>> + LIST_HEAD(temp_list_head);
> nit: I think our Xe maintainers prefer declarations in Reverse Christmas
> Tree Format
I though the rule is - uninitialized, then initialized. But I see all
possible conventions within the existing sources, so there just seem to
be no rule.
>> +
>> + lockdep_assert_held(&ggtt->lock);
>> +
>> + /*
>> + * Move nodes, from range previously assigned to this VF, into temp list.
>> + *
>> + * The balloon_beg and balloon_fin nodes are there to eliminate unavailable
>> + * ranges from use: first reserves the GGTT area below the range for current VF,
>> + * and second reserves area above. There may also exist extra nodes at the bottom
>> + * or top of GGTT range, as long as there are no free spaces inbetween. Such
>> + * extra nodes will be left unchanged.
>> + *
>> + * Below is a GGTT layout of example VF, with a certain address range assigned to
>> + * said VF, and inaccessible areas above and below:
>> + *
>> + * 0 ggtt->size
>> + * |<--------------------------- Total GGTT size ----------------------------->|
>> + *
>> + * +-----------+-------------------------+----------+--------------+-----------+
>> + * |\\\\\\\\\\\|/////////////////////////| VF mem |//////////////|\\\\\\\\\\\|
>> + * +-----------+-------------------------+----------+--------------+-----------+
>> + *
>> + * Hardware enforced access rules before migration:
>> + *
>> + * |<------- inaccessible for VF ------->|<VF owned>|<-- inaccessible for VF ->|
>> + *
>> + * drm_mm nodes used for tracking allocations:
>> + *
>> + * |<- extra ->|<------- balloon ------->|<- nodes->|<-- balloon ->|<- extra ->|
> in Xe we don't have 'extra' regions since xe_ggtt already covers only
> GuC accessible GGTT region, so it's like:
>
> 0 4GiB
> |<----------------- Total GGTT size ------------------------>|
>
> WOPCM GUC_TOP
> +-------+-------------------+-----------+------------+-------+
> |\\\\\\\|///////////////////| VF mem |////////////|\\\\\\\|
> +-------+-------------------+-----------+------------+-------+
>
> 0 ggtt->size
> |<--balloon-------->|<--nodes-->|<-balloon->|
will update.
>> + *
>> + * After the migration, GGTT area assigned to the VF might have shifted, either
>> + * to lower or to higher address. But we expect the total size and extra areas to
>> + * be identical, as migration can only happen between matching platforms.
>> + * Below is an example of GGTT layout of the VF after migration. Content of the
>> + * GGTT for VF has been moved to a new area, and we receive its address from GuC:
>> + *
>> + * +-----------+--------------+----------+-------------------------+-----------+
>> + * |\\\\\\\\\\\|//////////////| VF mem |/////////////////////////|\\\\\\\\\\\|
>> + * +-----------+--------------+----------+-------------------------+-----------+
>> + *
>> + * Hardware enforced access rules after migration:
>> + *
>> + * |<- inaccessible for VF -->|<VF owned>|<------- inaccessible for VF ------->|
>> + *
>> + * So the VF has a new slice of GGTT assigned, and during migration process, the
>> + * memory content was copied to that new area. But the drm_mm nodes within i915
> i915 ?
ack
>> + * are still tracking allocations using the old addresses. The nodes within VF
>> + * owned area have to be shifted, and balloon nodes need to be resized to
>> + * properly mask out areas not owned by the VF.
>> + *
>> + * Fixed drm_mm nodes used for tracking allocations:
> drm_mm nodes are implementation details of the xe_ggtt_nodes
You could equally say xe_ggtt_nodes are wrappers for drm_mm nodes.
Neither of these is going anywhere
for the lifetime of the driver within the kernel. And even calling these
approaches equal is a stretch.
It is easier to explain how something works using generic terms, and I'm
sure you agree drm_mm nodes are
more generic than the xe-specific wrappers.
The function is not fixing anything beyond the drm_mm - there are no
modifications to the xe decorator.
And note, vast majority of people reading the code will see the xe nodes
as just that - drm_mm node decorators.
>> + *
>> + * |<- extra ->|<- balloon ->|<-- VF -->|<-------- balloon ------>|<- extra ->|
>> + *
>> + * Due to use of GPU profiles, we do not expect the old and new GGTT ares to
>> + * overlap; but our node shifting will fix addresses properly regardless.
>> + *
>> + */
>> + drm_mm_for_each_node_in_range_safe(node, tmpn, &ggtt->mm,
>> + drm_mm_node_end(balloon_beg),
>> + balloon_fin->start) {
>> + drm_mm_remove_node(node);
>> + list_add(&node->node_list, &temp_list_head);
>> + }
>> +
>> + /* shift and re-add ballooning nodes */
>> + if (drm_mm_node_allocated(balloon_beg))
>> + drm_mm_remove_node(balloon_beg);
>> + if (drm_mm_node_allocated(balloon_fin))
>> + drm_mm_remove_node(balloon_fin);
>> + balloon_beg->size += shift;
>> + balloon_fin->start += shift;
>> + balloon_fin->size -= shift;
>> + if (balloon_beg->size != 0) {
>> + err = drm_mm_reserve_node(&ggtt->mm, balloon_beg);
>> + XE_WARN_ON(err);
>> + }
>> + if (balloon_fin->size != 0) {
>> + err = drm_mm_reserve_node(&ggtt->mm, balloon_fin);
>> + XE_WARN_ON(err);
> maybe xe_tile_assert() will work here?
sound good.
>> + }
>> +
>> + /*
>> + * Now the GGTT VM contains only nodes outside of area assigned to this VF.
>> + * We can re-add all VF nodes with shifted offsets.
>> + */
>> + list_for_each_entry_safe(node, tmpn, &temp_list_head, node_list) {
>> + list_del(&node->node_list);
>> + node->start += shift;
>> + err = drm_mm_reserve_node(&ggtt->mm, node);
>> + XE_WARN_ON(err);
> ditto
>
>> + }
>> +}
>> +
>> +static void xe_ggtt_node_shift_nodes(struct xe_ggtt *ggtt, struct xe_ggtt_node *balloon_beg,
>> + struct xe_ggtt_node *balloon_fin, s64 shift)
>> +{
>> + struct drm_mm_node *balloon_mm_beg, *balloon_mm_end;
>> + struct drm_mm_node loc_beg, loc_end;
>> +
>> + if (balloon_beg && balloon_beg->ggtt)
>> + balloon_mm_beg = &balloon_beg->base;
>> + else {
>> + loc_beg.color = 0;
>> + loc_beg.flags = 0;
>> + loc_beg.start = xe_wopcm_size(ggtt->tile->xe);
>> + loc_beg.size = 0;
>> + balloon_mm_beg = &loc_beg;
>> + }
>> +
>> + if (balloon_fin && balloon_fin->ggtt)
>> + balloon_mm_end = &balloon_fin->base;
>> + else {
>> + loc_end.color = 0;
>> + loc_end.flags = 0;
>> + loc_end.start = GUC_GGTT_TOP;
>> + loc_end.size = 0;
>> + balloon_mm_end = &loc_end;
>> + }
>> +
>> + drm_dbg(&ggtt->tile->xe->drm, "tli: node shift start beg %llx %llx end %llx %llx\n",
>> + balloon_mm_beg->start, balloon_mm_beg->size,
>> + balloon_mm_end->start, balloon_mm_end->size);
>> + xe_ggtt_mm_shift_nodes(ggtt, balloon_mm_beg, balloon_mm_end, shift);
>> + drm_dbg(&ggtt->tile->xe->drm, "tli: node shift end\n");
> tli ? looks like your private debug logs
yeah, forgot about these.
>> +}
>> +
>> +/**
>> + * xe_gt_sriov_vf_fixup_ggtt_nodes - Shift GGTT allocations to match assigned range.
>> + * @gt: the &xe_gt struct instance
>> + *
>> + * Since Global GTT is not virtualized, each VF has an assigned range
>> + * within the global space. This range might have changed during migration,
>> + * which requires all memory addresses pointing to GGTT to be shifted.
>> + */
>> +void xe_gt_sriov_vf_fixup_ggtt_nodes(struct xe_gt *gt)
>> +{
>> + struct xe_tile *tile = gt_to_tile(gt);
>> + struct xe_ggtt *ggtt = tile->mem.ggtt;
>> + s64 ggtt_shift;
>> +
>> + mutex_lock(&ggtt->lock);
>> + ggtt_shift = vf_get_post_migration_ggtt_shift(gt);
> do we still need to do anything if shift is 0?
Decreasing recovery time when possible does make sense. Will add a
condition.
>> + xe_ggtt_node_shift_nodes(ggtt, tile->sriov.vf.ggtt_balloon[0],
>> + tile->sriov.vf.ggtt_balloon[1], ggtt_shift);
>> + mutex_unlock(&ggtt->lock);
>> +}
>> +
>> static int vf_runtime_reg_cmp(const void *a, const void *b)
>> {
>> const struct vf_runtime_reg *ra = a;
>> diff --git a/drivers/gpu/drm/xe/xe_gt_sriov_vf.h b/drivers/gpu/drm/xe/xe_gt_sriov_vf.h
>> index 912d20814261..a8745ec23380 100644
>> --- a/drivers/gpu/drm/xe/xe_gt_sriov_vf.h
>> +++ b/drivers/gpu/drm/xe/xe_gt_sriov_vf.h
>> @@ -17,6 +17,7 @@ int xe_gt_sriov_vf_query_config(struct xe_gt *gt);
>> int xe_gt_sriov_vf_connect(struct xe_gt *gt);
>> int xe_gt_sriov_vf_query_runtime(struct xe_gt *gt);
>> int xe_gt_sriov_vf_prepare_ggtt(struct xe_gt *gt);
>> +void xe_gt_sriov_vf_fixup_ggtt_nodes(struct xe_gt *gt);
>> int xe_gt_sriov_vf_notify_resfix_done(struct xe_gt *gt);
>> void xe_gt_sriov_vf_migrated_event_handler(struct xe_gt *gt);
>>
>> diff --git a/drivers/gpu/drm/xe/xe_sriov_vf.c b/drivers/gpu/drm/xe/xe_sriov_vf.c
>> index c1275e64aa9c..5bcd55999e0e 100644
>> --- a/drivers/gpu/drm/xe/xe_sriov_vf.c
>> +++ b/drivers/gpu/drm/xe/xe_sriov_vf.c
>> @@ -7,6 +7,7 @@
>>
>> #include "xe_assert.h"
>> #include "xe_device.h"
>> +#include "xe_gt.h"
>> #include "xe_gt_sriov_printk.h"
>> #include "xe_gt_sriov_vf.h"
>> #include "xe_pm.h"
>> @@ -170,6 +171,19 @@ static bool vf_post_migration_imminent(struct xe_device *xe)
>> work_pending(&xe->sriov.vf.migration.worker);
>> }
>>
>> +static void vf_post_migration_fixup_ggtt_nodes(struct xe_device *xe)
>> +{
>> + struct xe_gt *gt;
>> + unsigned int id;
>> +
>> + for_each_gt(gt, xe, id) {
> maybe for_each_tile() would be a better fit here?
Since current platforms have ggtt per-tile rather than per-gt, it does
makes sense. Will change.
-Tomasz
>> + /* media doesn't have its own ggtt */
>> + if (xe_gt_is_media_type(gt))
>> + continue;
>> + xe_gt_sriov_vf_fixup_ggtt_nodes(gt);
>> + }
>> +}
>> +
>> /*
>> * Notify all GuCs about resource fixups apply finished.
>> */
>> @@ -201,6 +215,7 @@ static void vf_post_migration_recovery(struct xe_device *xe)
>> if (unlikely(err))
>> goto fail;
>>
>> + vf_post_migration_fixup_ggtt_nodes(xe);
>> /* FIXME: add the recovery steps */
>> vf_post_migration_notify_resfix_done(xe);
>> xe_pm_runtime_put(xe);
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