On Wed, Aug 04, 2021 at 09:47:08PM +0800, Dongdong Liu wrote: > Add a 10-Bit Tag check in the P2PDMA code to ensure that a device with > 10-Bit Tag Requester doesn't interact with a device that does not > support 10-BIT Tag Completer. Before that happens, the kernel should > emit a warning. "echo 0 > /sys/bus/pci/devices/.../10bit_tag" to > disable 10-BIT Tag Requester for PF device. > "echo 0 > /sys/bus/pci/devices/.../sriov_vf_10bit_tag_ctl" to disable > 10-BIT Tag Requester for VF device. s/10-BIT/10-Bit/ several times. Add blank lines between paragraphs. > Signed-off-by: Dongdong Liu <liudongdong3@xxxxxxxxxx> > --- > drivers/pci/p2pdma.c | 40 ++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 40 insertions(+) > > diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c > index 50cdde3..948f2be 100644 > --- a/drivers/pci/p2pdma.c > +++ b/drivers/pci/p2pdma.c > @@ -19,6 +19,7 @@ > #include <linux/random.h> > #include <linux/seq_buf.h> > #include <linux/xarray.h> > +#include "pci.h" > > enum pci_p2pdma_map_type { > PCI_P2PDMA_MAP_UNKNOWN = 0, > @@ -410,6 +411,41 @@ static unsigned long map_types_idx(struct pci_dev *client) > (client->bus->number << 8) | client->devfn; > } > > +static bool check_10bit_tags_vaild(struct pci_dev *a, struct pci_dev *b, s/vaild/valid/ Or maybe s/valid/safe/ or s/valid/supported/, since "valid" isn't quite the right word here. We want to know whether the source is enabled to generate 10-bit tags, and if so, whether the destination can handle them. "if (check_10bit_tags_valid())" does not make sense because "check_10bit_tags_valid()" is not a question with a yes/no answer. "10bit_tags_valid()" *might* be, because "if (10bit_tags_valid())" makes sense. But I don't think you can start with a digit. Or maybe you want to invert the sense, e.g., "10bit_tags_unsupported()", since that avoids negation at the caller: if (10bit_tags_unsupported(a, b) || 10bit_tags_unsupported(b, a)) map_type = PCI_P2PDMA_MAP_NOT_SUPPORTED; Doesn't this patch need to be at the very beginning, before you start enabling 10-bit tags? Otherwise there's a hole in the middle where we enable them and P2P DMA might break. > + bool verbose) > +{ > + bool req; > + bool comp; > + u16 ctl2; > + > + if (a->is_virtfn) { > +#ifdef CONFIG_PCI_IOV > + req = !!(a->physfn->sriov->ctrl & > + PCI_SRIOV_CTRL_VF_10BIT_TAG_REQ_EN); > +#endif > + } else { > + pcie_capability_read_word(a, PCI_EXP_DEVCTL2, &ctl2); > + req = !!(ctl2 & PCI_EXP_DEVCTL2_10BIT_TAG_REQ_EN); > + } > + > + comp = !!(b->pcie_devcap2 & PCI_EXP_DEVCAP2_10BIT_TAG_COMP); > + if (req && (!comp)) { > + if (verbose) { > + pci_warn(a, "cannot be used for peer-to-peer DMA as 10-Bit Tag Requester enable is set in device (%s), but peer device (%s) does not support the 10-Bit Tag Completer\n", > + pci_name(a), pci_name(b)); No point in printing pci_name(a) twice. pci_warn() prints it already; that should be enough. I think you can simplify this a little, e.g., if (!req) /* 10-bit tags not enabled on requester */ return true; if (comp) /* completer can handle anything */ return true; /* error case */ if (!verbose) return false; pci_warn(...); return false; > + if (a->is_virtfn) > + pci_warn(a, "to disable 10-Bit Tag Requester for this device, echo 0 > /sys/bus/pci/devices/%s/sriov_vf_10bit_tag_ctl\n", > + pci_name(a)); > + else > + pci_warn(a, "to disable 10-Bit Tag Requester for this device, echo 0 > /sys/bus/pci/devices/%s/10bit_tag\n", > + pci_name(a)); > + } > + return false; > + } > + > + return true; > +} > + > /* > * Calculate the P2PDMA mapping type and distance between two PCI devices. > * > @@ -532,6 +568,10 @@ calc_map_type_and_dist(struct pci_dev *provider, struct pci_dev *client, > map_type = PCI_P2PDMA_MAP_NOT_SUPPORTED; > } > done: > + if (!check_10bit_tags_vaild(client, provider, verbose) || > + !check_10bit_tags_vaild(provider, client, verbose)) > + map_type = PCI_P2PDMA_MAP_NOT_SUPPORTED; > + > rcu_read_lock(); > p2pdma = rcu_dereference(provider->p2pdma); > if (p2pdma) > -- > 2.7.4 >