On 2021-08-18 7:01 a.m., 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.
>
> Signed-off-by: Dongdong Liu <liudongdong3@xxxxxxxxxx>
Looks good to me, thanks.
Reviewed-by: Logan Gunthorpe <logang@xxxxxxxxxxxx>
> ---
> drivers/pci/p2pdma.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 48 insertions(+)
>
> diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c
> index 50cdde3..2b9c2c9 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 +411,50 @@ static unsigned long map_types_idx(struct pci_dev *client)
> (client->bus->number << 8) | client->devfn;
> }
>
> +static bool pci_10bit_tags_unsupported(struct pci_dev *a,
> + struct pci_dev *b,
> + bool verbose)
> +{
> + bool req;
> + bool comp;
> + u16 ctl;
> + const char *str = "10bit_tag";
> +
> + 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, &ctl);
> + req = !!(ctl & PCI_EXP_DEVCTL2_10BIT_TAG_REQ_EN);
> + }
> +
> + comp = !!(b->pcie_devcap2 & PCI_EXP_DEVCAP2_10BIT_TAG_COMP);
> +
> + /* 10-bit tags not enabled on requester */
> + if (!req)
> + return false;
> +
> + /* Completer can handle anything */
> + if (comp)
> + return false;
> +
> + if (!verbose)
> + return true;
> +
> + pci_warn(a, "cannot be used for peer-to-peer DMA as 10-Bit Tag Requester enable is set for this device, but peer device (%s) does not support the 10-Bit Tag Completer\n",
> + pci_name(b));
> +
> + if (a->is_virtfn)
> + str = "sriov_vf_10bit_tag_ctl";
> +
> + pci_warn(a, "to disable 10-Bit Tag Requester for this device, echo 0 > /sys/bus/pci/devices/%s/%s\n",
> + pci_name(a), str);
> +
> + return true;
> +}
> +
> /*
> * Calculate the P2PDMA mapping type and distance between two PCI devices.
> *
> @@ -532,6 +577,9 @@ calc_map_type_and_dist(struct pci_dev *provider, struct pci_dev *client,
> map_type = PCI_P2PDMA_MAP_NOT_SUPPORTED;
> }
> done:
> + if (pci_10bit_tags_unsupported(client, provider, verbose))
> + map_type = PCI_P2PDMA_MAP_NOT_SUPPORTED;
> +
> rcu_read_lock();
> p2pdma = rcu_dereference(provider->p2pdma);
> if (p2pdma)
>
