On Mon, 2026-02-09 at 08:58 -0800, Matthew Brost wrote: > On Mon, Feb 09, 2026 at 04:49:03PM +0100, Thomas Hellström wrote: > > On Wed, 2026-02-04 at 20:19 -0800, Matthew Brost wrote: > > > Split drm_pagemap_migrate_map_pages into device / system helpers > > > clearly > > > seperating these operations. Will help with upcoming changes to > > > split > > > IOVA allocation steps. > > > > > > Signed-off-by: Matthew Brost <[email protected]> > > > --- > > > drivers/gpu/drm/drm_pagemap.c | 146 ++++++++++++++++++++++------ > > > ---- > > > -- > > > 1 file changed, 96 insertions(+), 50 deletions(-) > > > > > > diff --git a/drivers/gpu/drm/drm_pagemap.c > > > b/drivers/gpu/drm/drm_pagemap.c > > > index fbd69f383457..29677b19bb69 100644 > > > --- a/drivers/gpu/drm/drm_pagemap.c > > > +++ b/drivers/gpu/drm/drm_pagemap.c > > > @@ -205,7 +205,7 @@ static void > > > drm_pagemap_get_devmem_page(struct > > > page *page, > > > } > > > > > > /** > > > - * drm_pagemap_migrate_map_pages() - Map migration pages for GPU > > > SVM > > > migration > > > + * drm_pagemap_migrate_map_device_pages() - Map device migration > > > pages for GPU SVM migration > > > * @dev: The device performing the migration. > > > * @local_dpagemap: The drm_pagemap local to the migrating > > > device. > > > * @pagemap_addr: Array to store DMA information corresponding > > > to > > > mapped pages. > > > @@ -221,19 +221,22 @@ static void > > > drm_pagemap_get_devmem_page(struct > > > page *page, > > > * > > > * Returns: 0 on success, -EFAULT if an error occurs during > > > mapping. > > > */ > > > -static int drm_pagemap_migrate_map_pages(struct device *dev, > > > - struct drm_pagemap > > > *local_dpagemap, > > > - struct drm_pagemap_addr > > > *pagemap_addr, > > > - unsigned long > > > *migrate_pfn, > > > - unsigned long npages, > > > - enum dma_data_direction > > > dir, > > > - const struct > > > drm_pagemap_migrate_details *mdetails) > > > +static int > > > +drm_pagemap_migrate_map_device_pages(struct device *dev, > > > + struct drm_pagemap > > > *local_dpagemap, > > > + struct drm_pagemap_addr > > > *pagemap_addr, > > > + unsigned long *migrate_pfn, > > > + unsigned long npages, > > > + enum dma_data_direction > > > dir, > > > + const struct > > > drm_pagemap_migrate_details *mdetails) > > > > We might want to call this device_private pages. Device coherent > > pages > > are treated like system pages here, but I figure those are known to > > the > > dma subsystem and can be handled by the map_system_pages callback. > > > > Yes. > > Eventually we will have figure out we'd want to handle Device > coherent > pages with a high speed fabric though. > > > > { > > > unsigned long num_peer_pages = 0, num_local_pages = 0, > > > i; > > > > > > for (i = 0; i < npages;) { > > > struct page *page = > > > migrate_pfn_to_page(migrate_pfn[i]); > > > - dma_addr_t dma_addr; > > > + struct drm_pagemap_zdd *zdd; > > > + struct drm_pagemap *dpagemap; > > > + struct drm_pagemap_addr addr; > > > struct folio *folio; > > > unsigned int order = 0; > > > > > > @@ -243,36 +246,26 @@ static int > > > drm_pagemap_migrate_map_pages(struct > > > device *dev, > > > folio = page_folio(page); > > > order = folio_order(folio); > > > > > > - if (is_device_private_page(page)) { > > > - struct drm_pagemap_zdd *zdd = > > > drm_pagemap_page_zone_device_data(page); > > > - struct drm_pagemap *dpagemap = zdd- > > > > dpagemap; > > > - struct drm_pagemap_addr addr; > > > - > > > - if (dpagemap == local_dpagemap) { > > > - if (!mdetails- > > > > can_migrate_same_pagemap) > > > - goto next; > > > + WARN_ON_ONCE(!is_device_private_page(page)); > > > > > > - num_local_pages += > > > NR_PAGES(order); > > > - } else { > > > - num_peer_pages += > > > NR_PAGES(order); > > > - } > > > + zdd = drm_pagemap_page_zone_device_data(page); > > > + dpagemap = zdd->dpagemap; > > > > > > - addr = dpagemap->ops- > > > >device_map(dpagemap, > > > dev, page, order, dir); > > > - if (dma_mapping_error(dev, addr.addr)) > > > - return -EFAULT; > > > + if (dpagemap == local_dpagemap) { > > > + if (!mdetails->can_migrate_same_pagemap) > > > + goto next; > > > > > > - pagemap_addr[i] = addr; > > > + num_local_pages += NR_PAGES(order); > > > } else { > > > - dma_addr = dma_map_page(dev, page, 0, > > > page_size(page), dir); > > > - if (dma_mapping_error(dev, dma_addr)) > > > - return -EFAULT; > > > - > > > - pagemap_addr[i] = > > > - > > > drm_pagemap_addr_encode(dma_addr, > > > - > > > DRM_INTE > > > RCONNECT_SYSTEM, > > > - order, > > > dir); > > > + num_peer_pages += NR_PAGES(order); > > > } > > > > > > + addr = dpagemap->ops->device_map(dpagemap, dev, > > > page, order, dir); > > > + if (dma_mapping_error(dev, addr.addr)) > > > + return -EFAULT; > > > + > > > + pagemap_addr[i] = addr; > > > + > > > next: > > > i += NR_PAGES(order); > > > } > > > @@ -287,6 +280,59 @@ static int > > > drm_pagemap_migrate_map_pages(struct > > > device *dev, > > > return 0; > > > } > > > > > > +/** > > > + * drm_pagemap_migrate_map_system_pages() - Map system migration > > > pages for GPU SVM migration > > > + * @dev: The device performing the migration. > > > + * @pagemap_addr: Array to store DMA information corresponding > > > to > > > mapped pages. > > > + * @migrate_pfn: Array of page frame numbers of system pages or > > > peer > > > pages to map. > > > > system pages or device coherent pages? "Peer" pages would typically > > be > > device-private pages with the same owner. > > > > > + * @npages: Number of system pages or peer pages to map. > > > > Same here. > > Yes, copy paste error. > > > > > > + * @dir: Direction of data transfer (e.g., DMA_BIDIRECTIONAL) > > > + * > > > + * This function maps pages of memory for migration usage in GPU > > > SVM. It > > > + * iterates over each page frame number provided in > > > @migrate_pfn, > > > maps the > > > + * corresponding page, and stores the DMA address in the > > > provided > > > @dma_addr > > > + * array. > > > + * > > > + * Returns: 0 on success, -EFAULT if an error occurs during > > > mapping. > > > + */ > > > +static int > > > +drm_pagemap_migrate_map_system_pages(struct device *dev, > > > + struct drm_pagemap_addr > > > *pagemap_addr, > > > + unsigned long *migrate_pfn, > > > + unsigned long npages, > > > + enum dma_data_direction > > > dir) > > > +{ > > > + unsigned long i; > > > + > > > + for (i = 0; i < npages;) { > > > + struct page *page = > > > migrate_pfn_to_page(migrate_pfn[i]); > > > + dma_addr_t dma_addr; > > > + struct folio *folio; > > > + unsigned int order = 0; > > > + > > > + if (!page) > > > + goto next; > > > + > > > + WARN_ON_ONCE(is_device_private_page(page)); > > > + folio = page_folio(page); > > > + order = folio_order(folio); > > > + > > > + dma_addr = dma_map_page(dev, page, 0, > > > page_size(page), dir); > > > + if (dma_mapping_error(dev, dma_addr)) > > > + return -EFAULT; > > > + > > > + pagemap_addr[i] = > > > + drm_pagemap_addr_encode(dma_addr, > > > + DRM_INTERCONNECT > > > _SYS > > > TEM, > > > + order, dir); > > > + > > > +next: > > > + i += NR_PAGES(order); > > > + } > > > + > > > + return 0; > > > +} > > > + > > > /** > > > * drm_pagemap_migrate_unmap_pages() - Unmap pages previously > > > mapped > > > for GPU SVM migration > > > * @dev: The device for which the pages were mapped > > > @@ -347,9 +393,11 @@ drm_pagemap_migrate_remote_to_local(struct > > > drm_pagemap_devmem *devmem, > > > const struct > > > drm_pagemap_migrate_details *mdetails) > > > > > > { > > > - int err = drm_pagemap_migrate_map_pages(remote_device, > > > remote_dpagemap, > > > - pagemap_addr, > > > local_pfns, > > > - npages, > > > DMA_FROM_DEVICE, mdetails); > > > + int err = > > > drm_pagemap_migrate_map_device_pages(remote_device, > > > + > > > remote_dpagemap, > > > + > > > pagemap_addr, > > > local_pfns, > > > + npages, > > > DMA_FROM_DEVICE, > > > + > > > mdetails); > > > > > > if (err) > > > goto out; > > > @@ -368,12 +416,11 @@ drm_pagemap_migrate_sys_to_dev(struct > > > drm_pagemap_devmem *devmem, > > > struct page *local_pages[], > > > struct drm_pagemap_addr > > > pagemap_addr[], > > > unsigned long npages, > > > - const struct > > > drm_pagemap_devmem_ops > > > *ops, > > > - const struct > > > drm_pagemap_migrate_details *mdetails) > > > + const struct > > > drm_pagemap_devmem_ops > > > *ops) > > > { > > > - int err = drm_pagemap_migrate_map_pages(devmem->dev, > > > devmem- > > > > dpagemap, > > > - pagemap_addr, > > > sys_pfns, npages, > > > - DMA_TO_DEVICE, > > > mdetails); > > > + int err = drm_pagemap_migrate_map_system_pages(devmem- > > > >dev, > > > + > > > pagemap_addr, > > > sys_pfns, > > > + npages, > > > DMA_TO_DEVICE); > > > > > > Unfortunately it's a bit more complicated than this. If the > > destination > > gpu migrates, the range to migrate could be a mix of system pages, > > device coherent pages and also device private pages, and previously > > drm_pagemap_migrate_map_pages() took care of that and did the > > correct > > thing on a per-page basis. > > > > You can exercise this by setting mdetails::source_peer_migrates to > > false on xe. That typically "works" but might generate some errors > > in > > the atomic multi-device tests AFAICT because reading from the BAR > > does > > not flush the L2 caches on BMG. But should be sufficient to > > exercise > > this path. > > Ah, yes I see I missed this - this patch isn't strickly required I > just > didn't want drm_pagemap_migrate_map_pages to have massive cascading > if > statements... I can remove for now if that is preferred or should be > just remove source_peer_migrates and assume a value of '1'. > > I suggest the later because looking forward source_peer_migrates == 0 > would bb difficult to support a high speed fabric, which requires a > IOVA > (think UAL with virtual NAs at the target device), plus multiple > different devices being found in the migration pages. Also, with p2p, > isn't source_peer_migrates == '1' (write over p2p) faster than > source_peer_migrates == '0' (read over p2p)?
With source_peer_migrates == 0 we have the drawbacks of missed cache flushing, can't be used with CCS compression, high speed fabric and also the speed over PCIe as you say, so I don't see xe using it in the near-term. So I agree. Let's just let's assume source_peer_migrates == 1 for now. Thanks, Thomas > > Matt > > > > > /Thomas
