Message-ID: <yuus76pxd2kcgkr2neoruxa3l24qudl6sezuq3tt5ctc5skter@67vmtfsgvolk>
Date: Tue, 28 Oct 2025 18:03:44 +0100
From: Michał Winiarski <michal.winiarski@...el.com>
To: Michal Wajdeczko <michal.wajdeczko@...el.com>
CC: Alex Williamson <alex.williamson@...hat.com>, Lucas De Marchi
	<lucas.demarchi@...el.com>, Thomas Hellström
	<thomas.hellstrom@...ux.intel.com>, Rodrigo Vivi <rodrigo.vivi@...el.com>,
	Jason Gunthorpe <jgg@...pe.ca>, Yishai Hadas <yishaih@...dia.com>, Kevin Tian
	<kevin.tian@...el.com>, <intel-xe@...ts.freedesktop.org>,
	<linux-kernel@...r.kernel.org>, <kvm@...r.kernel.org>, Matthew Brost
	<matthew.brost@...el.com>, <dri-devel@...ts.freedesktop.org>, Jani Nikula
	<jani.nikula@...ux.intel.com>, Joonas Lahtinen
	<joonas.lahtinen@...ux.intel.com>, Tvrtko Ursulin <tursulin@...ulin.net>,
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, "Lukasz
 Laguna" <lukasz.laguna@...el.com>
Subject: Re: [PATCH v2 16/26] drm/xe/pf: Add helpers for VF GGTT migration
 data handling

On Thu, Oct 23, 2025 at 11:50:28PM +0200, Michal Wajdeczko wrote:
> 
> 
> On 10/22/2025 12:41 AM, 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@...el.com>
> > ---
> >  drivers/gpu/drm/xe/xe_ggtt.c               | 100 +++++++++++++++++++++
> >  drivers/gpu/drm/xe/xe_ggtt.h               |   3 +
> >  drivers/gpu/drm/xe/xe_ggtt_types.h         |   2 +
> >  drivers/gpu/drm/xe/xe_gt_sriov_pf_config.c |  44 +++++++++
> >  drivers/gpu/drm/xe/xe_gt_sriov_pf_config.h |   5 ++
> >  5 files changed, 154 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/xe/xe_ggtt.c b/drivers/gpu/drm/xe/xe_ggtt.c
> > index 40680f0c49a17..99fe891c7939e 100644
> > --- a/drivers/gpu/drm/xe/xe_ggtt.c
> > +++ b/drivers/gpu/drm/xe/xe_ggtt.c
> > @@ -151,6 +151,14 @@ 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];
> > @@ -233,16 +241,19 @@ 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)
> > @@ -912,6 +923,22 @@ static void xe_ggtt_assign_locked(struct xe_ggtt *ggtt, const struct drm_mm_node
> >  	xe_ggtt_invalidate(ggtt);
> >  }
> >  
> > +/**
> > + * xe_ggtt_pte_size() - Convert GGTT VMA size to page table entries size.
> > + * @ggtt: the &xe_ggtt
> > + * @size: GGTT VMA size in bytes
> > + *
> > + * Return: GGTT page table entries size in bytes.
> > + */
> > +size_t xe_ggtt_pte_size(struct xe_ggtt *ggtt, size_t size)
> 
> passing ggtt just for assert seems overkill
> 
> > +{
> > +	struct xe_device __maybe_unused *xe = tile_to_xe(ggtt->tile);
> 
> we try to avoid __maybe_unused 
> 
> if you need xe/tile/gt just in the assert, then put to_xe/tile/gt inside it

It will go away after restructuring it to pass the node instead.

> 
> > +
> > +	xe_assert(xe, size % XE_PAGE_SIZE == 0);
> > +
> > +	return size / XE_PAGE_SIZE * sizeof(u64);
> > +}
> > +
> >  /**
> >   * xe_ggtt_assign - assign a GGTT region to the VF
> >   * @node: the &xe_ggtt_node to update
> > @@ -927,6 +954,79 @@ 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 &xe_ggtt_node to a buffer.
> > + * @node: the &xe_ggtt_node to be saved
> > + * @dst: destination buffer
> > + * @size: destination buffer size in bytes
> > + *
> > + * 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)
> > +		return -ENOENT;
> > +
> > +	guard(mutex)(&node->ggtt->lock);
> > +
> > +	ggtt = node->ggtt;
> > +	start = node->base.start;
> > +	end = start + node->base.size - 1;
> > +
> > +	if (xe_ggtt_pte_size(ggtt, node->base.size) > size)
> > +		return -EINVAL;
> > +
> > +	while (start < end) {
> > +		*buf++ = ggtt->pt_ops->ggtt_get_pte(ggtt, start) & ~GGTT_PTE_VFID;
> 
> up to this point function is generic, non-IOV, so maybe leave PTEs as-is and do not sanitize VFID ?
> 
> or, similar to node_load(), also pass vfid to enforce additional checks ?
> 
> 	pte = ggtt->pt_ops->ggtt_get_pte(ggtt, start);
> 	if (vfid != u64_get_bits(pte, GGTT_PTE_VFID))
> 		return -EPERM;
> 
> then optionally sanitize using:
> 
> 	*buf++ = u64_replace_bits(pte, 0, GGTT_PTE_VFID);
> 

I'll go with check & sanitize.

> 
> 
> > +		start += XE_PAGE_SIZE;
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +/**
> > + * xe_ggtt_node_load() - Load a &xe_ggtt_node from a buffer.
> > + * @node: the &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)
> > +{
> > +	u64 vfid_pte = xe_encode_vfid_pte(vfid);
> > +	const u64 *buf = src;
> > +	struct xe_ggtt *ggtt;
> > +	u64 start, end;
> > +
> > +	if (!node)
> > +		return -ENOENT;
> > +
> > +	guard(mutex)(&node->ggtt->lock);
> > +
> > +	ggtt = node->ggtt;
> > +	start = node->base.start;
> > +	end = start + size - 1;
> > +
> > +	if (xe_ggtt_pte_size(ggtt, node->base.size) != size)
> > +		return -EINVAL;
> > +
> > +	while (start < end) {
> > +		ggtt->pt_ops->ggtt_set_pte(ggtt, start, (*buf & ~GGTT_PTE_VFID) | vfid_pte);
> 
> 		pte = u64_replace_bits(*buf++, vfid, GGTT_PTE_VFID));
> 		ggtt_set_pte(ggtt, start, pte);
> 

Ok.

> > +		start += XE_PAGE_SIZE;
> > +		buf++;
> > +	}
> > +	xe_ggtt_invalidate(ggtt);
> > +
> > +	return 0;
> > +}
> > +
> >  #endif
> >  
> >  /**
> > diff --git a/drivers/gpu/drm/xe/xe_ggtt.h b/drivers/gpu/drm/xe/xe_ggtt.h
> > index 75fc7a1efea76..5f55f80fe3adc 100644
> > --- a/drivers/gpu/drm/xe/xe_ggtt.h
> > +++ b/drivers/gpu/drm/xe/xe_ggtt.h
> > @@ -42,7 +42,10 @@ int xe_ggtt_dump(struct xe_ggtt *ggtt, struct drm_printer *p);
> >  u64 xe_ggtt_print_holes(struct xe_ggtt *ggtt, u64 alignment, struct drm_printer *p);
> >  
> >  #ifdef CONFIG_PCI_IOV
> > +size_t xe_ggtt_pte_size(struct xe_ggtt *ggtt, size_t size);
> 
> this could be generic (non PCI-IOV only) inline helper or macro here or in .c
> 
> 	size_t to_xe_ggtt_pt_size(size_t size);
> 
> and then more elegant solution would be to expose
> 
> 	size_t xe_ggtt_node_pt_size(const struct xe_ggtt_node *node);
> 
> and yes, that would require to additionally expose something from gt_sriov_pf_config
> as migration code doesn't have access to this node,
> 
> but maybe xe_gt_sriov_pf_config_ggtt_save() can be updated to also support 'query' mode?
> 
> 	size_t xe_gt_sriov_pf_config_ggtt_save(gt, vfid, buf, size) -> bytes saved
> 	size_t xe_gt_sriov_pf_config_ggtt_save(gt, vfid, NULL, 0) -> size to be saved

Ok.
I'll go with passing NULL and 0 to query.

Thanks,
-Michał

> 
> 
> >  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 c0c0215c07036..c857879e28fe5 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 +726,50 @@ 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 &xe_gt
> > + * @vfid: VF identifier (can't be 0)
> > + * @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)
> > +{
> > +	xe_gt_assert(gt, IS_SRIOV_PF(gt_to_xe(gt)));
> > +	xe_gt_assert(gt, vfid);
> > +
> > +	guard(mutex)(xe_gt_sriov_pf_master_mutex(gt));
> > +
> > +	return xe_ggtt_node_save(pf_pick_vf_config(gt, vfid)->ggtt_region, buf, size);
> > +}
> > +
> > +/**
> > + * xe_gt_sriov_pf_config_ggtt_restore() - Restore a VF provisioned GGTT data from a buffer.
> > + * @gt: the &xe_gt
> > + * @vfid: VF identifier (can't be 0)
> > + * @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)
> > +{
> > +	xe_gt_assert(gt, IS_SRIOV_PF(gt_to_xe(gt)));
> > +	xe_gt_assert(gt, vfid);
> > +
> > +	guard(mutex)(xe_gt_sriov_pf_master_mutex(gt));
> > +
> > +	return xe_ggtt_node_load(pf_pick_vf_config(gt, vfid)->ggtt_region, buf, size, vfid);
> > +}
> > +
> >  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);
> 

Powered by blists - more mailing lists