On Thu, Oct 01, 2026 at 12:07:56PM +0000, [email protected] wrote: > Thank you for your contribution! Sashiko AI review found 1 potential issue(s) > to consider: > - [High] pci/p2pdma: pcim_p2pdma_set_ats_per_mapping() silently fails for > pure clients > -- > > commit 39432dea495f68fb0a21d0daa1f31ba24e130b39 > Author: Leon Romanovsky <[email protected]> > > PCI/P2PDMA: Evaluate the ATS path for clients with ATS enabled > > P2PDMA assumes every client issues Untranslated Requests. A device with > ATS enabled may translate any address it is handed, including a bus > address, and Translation Blocking can reject its Translated Requests on > a route the Untranslated answer called usable. This commit takes the > Address Type from its ATS Enable bit and avoids handing such a client > bus addresses unless the client declared per-mapping ATS. > > > diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c > > index 6a63901c65fb6..9c0943fdb3e36 100644 > > --- a/drivers/pci/p2pdma.c > > +++ b/drivers/pci/p2pdma.c > [ ... ] > > @@ -1633,6 +1674,9 @@ pci_p2pdma_map_type_tlp(struct p2pdma_provider > > *provider, struct device *dev, > > cache_index = map_types_idx(client); > > > > rcu_read_lock(); > > + /* The declaration belongs to the client, the cache to the provider. */ > > + p2pdma = rcu_dereference(client->p2pdma); > > + per_mapping = p2pdma && p2pdma->ats_per_mapping; > > [Severity: High] > Does this code handle pure P2PDMA clients correctly? > > Since pure clients (devices initiating P2P transfers but not providing memory) > have no mechanism or reason to call pcim_p2pdma_init(), client->p2pdma will > be NULL for them. > > This means when they call pcim_p2pdma_set_ats_per_mapping(), it silently > returns > and drops the configuration: > > drivers/pci/p2pdma.c:pcim_p2pdma_set_ats_per_mapping() { > ... > p2p = rcu_dereference_protected(pdev->p2pdma, 1); > if (!p2p) > /* > * ats_per_mapping is a performance optimization, > ... > */ > return; > > p2p->ats_per_mapping = true; > } > > Because client->p2pdma is NULL, per_mapping will always evaluate to false > here in pci_p2pdma_map_type_tlp(). This leads to pci_p2pdma_client_map_type() > incorrectly overriding the map type, which could return > PCI_P2PDMA_MAP_NOT_SUPPORTED and break P2P transfers that should have been > permitted. > > How should pure clients register their ATS per-mapping capability if they > do not initialize pdev->p2pdma?
I don't know there Sashiko gets these ideas, but no "pure client" shouldn't call to pcim_p2pdma_set_ats_per_mapping(). Thanks > > > p2pdma = rcu_dereference(pdev->p2pdma); > > > > if (p2pdma) > > -- > Sashiko AI review ยท > https://sashiko.dev/#/patchset/[email protected]?part=17
