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Message-ID: <20240702145806.0000669b@Huawei.com>
Date: Tue, 2 Jul 2024 14:58:06 +0100
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: Alistair Francis <alistair23@...il.com>
CC: <bhelgaas@...gle.com>, <linux-pci@...r.kernel.org>, <lukas@...ner.de>,
<alex.williamson@...hat.com>, <christian.koenig@....com>, <kch@...dia.com>,
<gregkh@...uxfoundation.org>, <logang@...tatee.com>,
<linux-kernel@...r.kernel.org>, <chaitanyak@...dia.com>,
<rdunlap@...radead.org>, Alistair Francis <alistair.francis@....com>
Subject: Re: [PATCH v13 3/4] PCI/DOE: Expose the DOE features via sysfs
On Tue, 2 Jul 2024 16:04:17 +1000
Alistair Francis <alistair23@...il.com> wrote:
> The PCIe 6 specification added support for the Data Object
> Exchange (DOE).
> When DOE is supported the DOE Discovery Feature must be implemented per
> PCIe r6.1 sec 6.30.1.1. The protocol allows a requester to obtain
> information about the other DOE features supported by the device.
>
> The kernel is already querying the DOE features supported and cacheing
> the values. Expose the values in sysfs to allow user space to
> determine which DOE features are supported by the PCIe device.
>
> By exposing the information to userspace tools like lspci can relay the
> information to users. By listing all of the supported features we can
> allow userspace to parse the list, which might include
> vendor specific features as well as yet to be supported features.
>
> After this patch is supported you can see something like this when
> attaching a DOE device
>
> $ ls /sys/devices/pci0000:00/0000:00:02.0//doe*
> 0001:00 0001:01 0001:02
>
> Signed-off-by: Alistair Francis <alistair.francis@....com>
> ---
> v13:
> - Drop pci_doe_sysfs_init() and use pci_doe_sysfs_group
> - As discussed in https://lore.kernel.org/all/20231019165829.GA1381099@bhelgaas/
> we can just modify pci_doe_sysfs_group at the DOE init and let
Can't do that as it is global so you expose the same DOE features for
all DOEs.
Also, I think that this is only processing features on last doe_mb found
for a given device. Fix that and the duplicates problem resurfaces.
> device_add() handle the sysfs attributes.
> diff --git a/drivers/pci/doe.c b/drivers/pci/doe.c
> index defc4be81bd4..e7b702afce88 100644
> --- a/drivers/pci/doe.c
> +++ b/drivers/pci/doe.c
> +
> static int pci_doe_wait(struct pci_doe_mb *doe_mb, unsigned long timeout)
> {
> if (wait_event_timeout(doe_mb->wq,
> @@ -687,6 +747,12 @@ void pci_doe_init(struct pci_dev *pdev)
> {
> struct pci_doe_mb *doe_mb;
> u16 offset = 0;
> + struct attribute **sysfs_attrs;
> + struct device_attribute *attrs;
> + unsigned long num_features = 0;
> + unsigned long i;
> + unsigned long vid, type;
> + void *entry;
> int rc;
>
> xa_init(&pdev->doe_mbs);
> @@ -707,6 +773,45 @@ void pci_doe_init(struct pci_dev *pdev)
> pci_doe_destroy_mb(doe_mb);
> }
> }
The above is looping over multiple DOEs but this just considers last one.
That doesn't look right...
I think this needs to be in the loop and having done that
the duplicate handing may be an issue. I'm not sure what happens
in that path with a presupplied set of attributes.
> +
> + if (doe_mb) {
> + xa_for_each(&doe_mb->feats, i, entry)
> + num_features++;
> +
> + sysfs_attrs = kcalloc(num_features + 1, sizeof(*sysfs_attrs), GFP_KERNEL);
> + if (!sysfs_attrs)
> + return;
> +
> + attrs = kcalloc(num_features, sizeof(*attrs), GFP_KERNEL);
> + if (!attrs) {
> + kfree(sysfs_attrs);
> + return;
> + }
> +
> + doe_mb->device_attrs = attrs;
> + doe_mb->sysfs_attrs = sysfs_attrs;
> +
> + xa_for_each(&doe_mb->feats, i, entry) {
> + sysfs_attr_init(&attrs[i].attr);
> +
> + vid = xa_to_value(entry) >> 8;
> + type = xa_to_value(entry) & 0xFF;
> +
> + attrs[i].attr.name = kasprintf(GFP_KERNEL, "%04lx:%02lx", vid, type);
> + if (!attrs[i].attr.name) {
> + pci_doe_sysfs_feature_remove(pdev, doe_mb);
> + return;
> + }
> + attrs[i].attr.mode = 0444;
> + attrs[i].show = pci_doe_sysfs_feature_show;
> +
> + sysfs_attrs[i] = &attrs[i].attr;
> + }
> +
> + sysfs_attrs[num_features] = NULL;
> +
> + pci_doe_sysfs_group.attrs = sysfs_attrs;
Hmm. Isn't this global? What if you have multiple devices.
> + }
> }
>
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