Re: [PATCH V7 9/9] PCI/P2PDMA: Add a 10-Bit Tag check in P2PDMA
flat view
From: Bjorn Helgaas <helgaas@kernel.org>
Date: 2021-08-05 18:12:36
Also in:
linux-media, linux-pci
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.
quoted hunk ↗ jump to hunk
Signed-off-by: Dongdong Liu <redacted> --- 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.
quoted hunk ↗ jump to hunk
+ 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;
quoted hunk ↗ jump to hunk
+ 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