Re: [PATCH 17/26] drm/xe/pf: Add helpers for VF GGTT migration data handling

Michał Winiarski
2025-10-21T01:00:29Z

On Mon, Oct 13, 2025 at 02:17:56PM +0200, Michal Wajdeczko wrote:
>
>
> On 10/11/2025 9:38 PM, Michał Winiarski wrote:
> > In an upcoming change, the VF GGTT migration data will be handled as
> > part of VF control state machine. Add the necessary helpers to allow the
> > migration data transfer to/from the HW GGTT resource.
> >
> > Signed-off-by: Michał Winiarski <michal.winiarski@intel.com>
> > ---
> > drivers/gpu/drm/xe/xe_ggtt.c | 92 ++++++++++++++++++++++
> > drivers/gpu/drm/xe/xe_ggtt.h | 2 +
> > drivers/gpu/drm/xe/xe_ggtt_types.h | 2 +
> > drivers/gpu/drm/xe/xe_gt_sriov_pf_config.c | 64 +++++++++++++++
> > drivers/gpu/drm/xe/xe_gt_sriov_pf_config.h | 5 ++
> > 5 files changed, 165 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/xe/xe_ggtt.c b/drivers/gpu/drm/xe/xe_ggtt.c
> > index aca7ae5489b91..89c0ad56c6a8a 100644
> > --- a/drivers/gpu/drm/xe/xe_ggtt.c
> > +++ b/drivers/gpu/drm/xe/xe_ggtt.c
> > @@ -138,6 +138,14 @@ static void xe_ggtt_set_pte_and_flush(struct xe_ggtt *ggtt, u64 addr, u64 pte)
> > ggtt_update_access_counter(ggtt);
> > }
> >
> > +static u64 xe_ggtt_get_pte(struct xe_ggtt *ggtt, u64 addr)
> > +{
> > + xe_tile_assert(ggtt->tile, !(addr & XE_PTE_MASK));
> > + xe_tile_assert(ggtt->tile, addr < ggtt->size);
> > +
> > + return readq(&ggtt->gsm[addr >> XE_PTE_SHIFT]);
> > +}
> > +
> > static void xe_ggtt_clear(struct xe_ggtt *ggtt, u64 start, u64 size)
> > {
> > u16 pat_index = tile_to_xe(ggtt->tile)->pat.idx[XE_CACHE_WB];
> > @@ -220,16 +228,19 @@ void xe_ggtt_might_lock(struct xe_ggtt *ggtt)
> > static const struct xe_ggtt_pt_ops xelp_pt_ops = {
> > .pte_encode_flags = xelp_ggtt_pte_flags,
> > .ggtt_set_pte = xe_ggtt_set_pte,
> > + .ggtt_get_pte = xe_ggtt_get_pte,
> > };
> >
> > static const struct xe_ggtt_pt_ops xelpg_pt_ops = {
> > .pte_encode_flags = xelpg_ggtt_pte_flags,
> > .ggtt_set_pte = xe_ggtt_set_pte,
> > + .ggtt_get_pte = xe_ggtt_get_pte,
> > };
> >
> > static const struct xe_ggtt_pt_ops xelpg_pt_wa_ops = {
> > .pte_encode_flags = xelpg_ggtt_pte_flags,
> > .ggtt_set_pte = xe_ggtt_set_pte_and_flush,
> > + .ggtt_get_pte = xe_ggtt_get_pte,
> > };
> >
> > static void __xe_ggtt_init_early(struct xe_ggtt *ggtt, u32 reserved)
> > @@ -914,6 +925,87 @@ void xe_ggtt_assign(const struct xe_ggtt_node *node, u16 vfid)
> > xe_ggtt_assign_locked(node->ggtt, &node->base, vfid);
> > mutex_unlock(&node->ggtt->lock);
> > }
> > +
> > +/**
> > + * xe_ggtt_node_save - Save a &struct xe_ggtt_node to a buffer
> > + * @node: the &struct xe_ggtt_node to be saved
> > + * @dst: destination buffer
>
> correct me: this is buffer for the PTEs
>
> > + * @size: destination buffer size in bytes
>
> and this is size of above buffer
>
> > + *
> > + * Return: 0 on success or a negative error code on failure.
> > + */
> > +int xe_ggtt_node_save(struct xe_ggtt_node *node, void *dst, size_t size)
> > +{
> > + struct xe_ggtt *ggtt;
> > + u64 start, end;
> > + u64 *buf = dst;
> > +
> > + if (!node || !node->ggtt)
> > + return -ENOENT;
>
> hmm, non-NULL node must be initialized by xe_ggtt_node_init() which sets the .ggtt so this second check is redundant

Ok.

>
> > +
> > + mutex_lock(&node->ggtt->lock);
>
> guard(mutex)(&node->ggtt->lock);

Ok.

>
> > +
> > + ggtt = node->ggtt;
> > + start = node->base.start;
> > + end = start + node->base.size - 1;
> > +
> > + if (node->base.size < size) {
>
> so that's looks wrong, we are about to save 64bit PTEs of that node
>
> we should compare size of all PTEs not the size of address space allocated by this node

I'll replace it with

if (xe_ggtt_pte_size(ggtt, size: node->base.size) > size)
return -EINVAL;

>
> > + mutex_unlock(&node->ggtt->lock);
> > + return -EINVAL;
> > + }
> > +
> > + while (start < end) {
> > + *buf++ = ggtt->pt_ops->ggtt_get_pte(ggtt, start) & ~GGTT_PTE_VFID;
> > + start += XE_PAGE_SIZE;
> > + }
> > +
> > + mutex_unlock(&node->ggtt->lock);
> > +
> > + return 0;
> > +}
> > +
> > +/**
> > + * xe_ggtt_node_load - Load a &struct xe_ggtt_node from a buffer
> > + * @node: the &struct xe_ggtt_node to be loaded
> > + * @src: source buffer
> > + * @size: source buffer size in bytes
> > + * @vfid: VF identifier
> > + *
> > + * Return: 0 on success or a negative error code on failure.
> > + */
> > +int xe_ggtt_node_load(struct xe_ggtt_node *node, const void *src, size_t size, u16 vfid)
> > +{
> > + struct xe_ggtt *ggtt;
> > + u64 start, end;
> > + const u64 *buf = src;
> > + u64 vfid_pte = xe_encode_vfid_pte(vfid);
>
> try to define vars in reverse xmas tree order

Ok.

>
> > +
> > + if (!node || !node->ggtt)
> > + return -ENOENT;
> > +
> > + mutex_lock(&node->ggtt->lock);
>
> use guard(mutex)

Ok.

>
> > +
> > + ggtt = node->ggtt;
> > + start = node->base.start;
> > + end = start + size - 1;
> > +
> > + if (node->base.size != size) {
> > + mutex_unlock(&node->ggtt->lock);
> > + return -EINVAL;
> > + }
> > +
> > + while (start < end) {
> > + ggtt->pt_ops->ggtt_set_pte(ggtt, start, (*buf & ~GGTT_PTE_VFID) | vfid_pte);
> > + start += XE_PAGE_SIZE;
> > + buf++;
> > + }
> > + xe_ggtt_invalidate(ggtt);
> > +
> > + mutex_unlock(&node->ggtt->lock);
> > +
> > + return 0;
> > +}
> > +
> > #endif
> >
> > /**
> > diff --git a/drivers/gpu/drm/xe/xe_ggtt.h b/drivers/gpu/drm/xe/xe_ggtt.h
> > index 75fc7a1efea76..469b3a6ca14b4 100644
> > --- a/drivers/gpu/drm/xe/xe_ggtt.h
> > +++ b/drivers/gpu/drm/xe/xe_ggtt.h
> > @@ -43,6 +43,8 @@ u64 xe_ggtt_print_holes(struct xe_ggtt *ggtt, u64 alignment, struct drm_printer
> >
> > #ifdef CONFIG_PCI_IOV
> > void xe_ggtt_assign(const struct xe_ggtt_node *node, u16 vfid);
> > +int xe_ggtt_node_save(struct xe_ggtt_node *node, void *dst, size_t size);
> > +int xe_ggtt_node_load(struct xe_ggtt_node *node, const void *src, size_t size, u16 vfid);
> > #endif
> >
> > #ifndef CONFIG_LOCKDEP
> > diff --git a/drivers/gpu/drm/xe/xe_ggtt_types.h b/drivers/gpu/drm/xe/xe_ggtt_types.h
> > index c5e999d58ff2a..dacd796f81844 100644
> > --- a/drivers/gpu/drm/xe/xe_ggtt_types.h
> > +++ b/drivers/gpu/drm/xe/xe_ggtt_types.h
> > @@ -78,6 +78,8 @@ struct xe_ggtt_pt_ops {
> > u64 (*pte_encode_flags)(struct xe_bo *bo, u16 pat_index);
> > /** @ggtt_set_pte: Directly write into GGTT's PTE */
> > void (*ggtt_set_pte)(struct xe_ggtt *ggtt, u64 addr, u64 pte);
> > + /** @ggtt_get_pte: Directly read from GGTT's PTE */
> > + u64 (*ggtt_get_pte)(struct xe_ggtt *ggtt, u64 addr);
> > };
> >
> > #endif
> > diff --git a/drivers/gpu/drm/xe/xe_gt_sriov_pf_config.c b/drivers/gpu/drm/xe/xe_gt_sriov_pf_config.c
> > index b2e5c52978e6a..51027921b2988 100644
> > --- a/drivers/gpu/drm/xe/xe_gt_sriov_pf_config.c
> > +++ b/drivers/gpu/drm/xe/xe_gt_sriov_pf_config.c
> > @@ -726,6 +726,70 @@ int xe_gt_sriov_pf_config_set_fair_ggtt(struct xe_gt *gt, unsigned int vfid,
> > return xe_gt_sriov_pf_config_bulk_set_ggtt(gt, vfid, num_vfs, fair);
> > }
> >
> > +/**
> > + * xe_gt_sriov_pf_config_ggtt_save - Save a VF provisioned GGTT data into a buffer.
> > + * @gt: the &struct xe_gt
> > + * @vfid: VF identifier
> > + * @buf: the GGTT data destination buffer
> > + * @size: the size of the buffer
> > + *
> > + * This function can only be called on PF.
> > + *
> > + * Return: 0 on success or a negative error code on failure.
> > + */
> > +int xe_gt_sriov_pf_config_ggtt_save(struct xe_gt *gt, unsigned int vfid,
> > + void *buf, size_t size)
> > +{
> > + struct xe_gt_sriov_config *config;
> > + ssize_t ret;
>
> int
>
> > +
> > + xe_gt_assert(gt, IS_SRIOV_PF(gt_to_xe(gt)));
> > + xe_gt_assert(gt, vfid);
> > + xe_gt_assert(gt, !(!buf ^ !size));
>
> there seems to be no "query" option for this call, so both buf & size must be valid
>
> > +
> > + mutex_lock(xe_gt_sriov_pf_master_mutex(gt));
> > + config = pf_pick_vf_config(gt, vfid);
> > + size = size / sizeof(u64) * XE_PAGE_SIZE;
>
> ?? something is wrong here - why do we have to change the size of the buf?

Should be simplified after tweaking the logic with size conversions
to/from PTE.

>
> > +
> > + ret = xe_ggtt_node_save(config->ggtt_region, buf, size);
> > +
> > + mutex_unlock(xe_gt_sriov_pf_master_mutex(gt));
> > +
> > + return ret;
> > +}
> > +
> > +/**
> > + * xe_gt_sriov_pf_config_ggtt_restore - Restore a VF provisioned GGTT data from a buffer.
> > + * @gt: the &struct xe_gt
> > + * @vfid: VF identifier
> > + * @buf: the GGTT data source buffer
> > + * @size: the size of the buffer
> > + *
> > + * This function can only be called on PF.
> > + *
> > + * Return: 0 on success or a negative error code on failure.
> > + */
> > +int xe_gt_sriov_pf_config_ggtt_restore(struct xe_gt *gt, unsigned int vfid,
> > + const void *buf, size_t size)
> > +{
> > + struct xe_gt_sriov_config *config;
> > + ssize_t ret;
> > +
> > + xe_gt_assert(gt, IS_SRIOV_PF(gt_to_xe(gt)));
> > + xe_gt_assert(gt, vfid);
> > + xe_gt_assert(gt, !(!buf ^ !size));
> > +
> > + mutex_lock(xe_gt_sriov_pf_master_mutex(gt));
> > + config = pf_pick_vf_config(gt, vfid);
> > + size = size / sizeof(u64) * XE_PAGE_SIZE;
> > +
> > + ret = xe_ggtt_node_load(config->ggtt_region, buf, size, vfid);
> > +
> > + mutex_unlock(xe_gt_sriov_pf_master_mutex(gt));
> > +
> > + return ret;
> > +}
>
> ditto

Ok.

Thanks,
-Michał

>
> > +
> > static u32 pf_get_min_spare_ctxs(struct xe_gt *gt)
> > {
> > /* XXX: preliminary */
> > diff --git a/drivers/gpu/drm/xe/xe_gt_sriov_pf_config.h b/drivers/gpu/drm/xe/xe_gt_sriov_pf_config.h
> > index 513e6512a575b..6916b8f58ebf2 100644
> > --- a/drivers/gpu/drm/xe/xe_gt_sriov_pf_config.h
> > +++ b/drivers/gpu/drm/xe/xe_gt_sriov_pf_config.h
> > @@ -61,6 +61,11 @@ ssize_t xe_gt_sriov_pf_config_save(struct xe_gt *gt, unsigned int vfid, void *bu
> > int xe_gt_sriov_pf_config_restore(struct xe_gt *gt, unsigned int vfid,
> > const void *buf, size_t size);
> >
> > +int xe_gt_sriov_pf_config_ggtt_save(struct xe_gt *gt, unsigned int vfid,
> > + void *buf, size_t size);
> > +int xe_gt_sriov_pf_config_ggtt_restore(struct xe_gt *gt, unsigned int vfid,
> > + const void *buf, size_t size);
> > +
> > bool xe_gt_sriov_pf_config_is_empty(struct xe_gt *gt, unsigned int vfid);
> >
> > int xe_gt_sriov_pf_config_init(struct xe_gt *gt);
>