On Sat, Aug 07, 2021 at 03:11:34PM +0800, Dongdong Liu wrote: > > On 2021/8/6 2:12, Bjorn Helgaas wrote: > > 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. > Will fix. > > > > Add blank lines between paragraphs. > Will fix. > > > > > 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; > Good suggestion. add a pci_ prefix. > > if (pci_10bit_tags_unsupported(a, b) || > pci_10bit_tags_unsupported(b, a)) > map_type = PCI_P2PDMA_MAP_NOT_SUPPORTED; This treats both directions as equally important. I don't know P2PDMA very well, but that doesn't seem like it would necessarily be the case. I would think a common case would be device A doing DMA to B, but B *not* doing DMA to A. So can you tell which direction you're setting up here, and can you take advantage of any asymmetry, e.g., by enabling 10-bit tags in the direction that supports it even if the other direction does not?