On 2021/10/28 5:20, Bjorn Helgaas wrote:
On Sat, Oct 09, 2021 at 06:49:36PM +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.
Shouldn't this also take into account Extended Tags (8 bits)? I think
the only tag size guaranteed to be supported is 5 bits.
As all PCIe completers are required to support 8-bit tags, seems no need
to take into account Extended Tags.
Before that happens, the kernel should emit a warning.
The warning is nice, but the critical thing is that the P2PDMA mapping
should fail so we don't attempt DMA in this situation. I guess that's
sort of what you're saying with "ensure that a device ... doesn't
interact with a device ..."
Yes, that is.
"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>
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 50cdde3e9a8b..804e390f4c22 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->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)
--
2.22.0
.
