Re: [PATCH 09/11] PCI/IDE: Report available IDE streams

[Dan Williams <dan.j.williams@intel.com>]

Alexey Kardashevskiy wrote:
> On 6/12/24 09:24, Dan Williams wrote:
> > The limited number of link-encryption (IDE) streams that a given set of
> > host-bridges supports is a platform specific detail. Provide
> > pci_set_nr_ide_streams() as a generic facility for either platform TSM
> > drivers, or in the future PCI core native IDE, to report the number
> > available streams. After invoking pci_set_nr_ide_streams() an
> > "available_secure_streams" attribute appears in PCI Host Bridge sysfs to
> > convey how many streams are available for IDE establishment.
> > 
> > Cc: Bjorn Helgaas <bhelgaas@google.com>
> > Cc: Lukas Wunner <lukas@wunner.de>
> > Cc: Samuel Ortiz <sameo@rivosinc.com>
> > Cc: Alexey Kardashevskiy <aik@amd.com>
> > Cc: Xu Yilun <yilun.xu@linux.intel.com>
> > Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> > ---
> >   .../ABI/testing/sysfs-devices-pci-host-bridge      |   11 +++++
> >   drivers/pci/ide.c                                  |   46 ++++++++++++++++++++
> >   drivers/pci/pci.h                                  |    3 +
> >   drivers/pci/probe.c                                |   11 ++++-
> >   include/linux/pci.h                                |    9 ++++
> >   5 files changed, 79 insertions(+), 1 deletion(-)
> > 
> > diff --git a/Documentation/ABI/testing/sysfs-devices-pci-host-bridge b/Documentation/ABI/testing/sysfs-devices-pci-host-bridge
> > index 15dafb46b176..1a3249f20e48 100644
> > --- a/Documentation/ABI/testing/sysfs-devices-pci-host-bridge
> > +++ b/Documentation/ABI/testing/sysfs-devices-pci-host-bridge
> > @@ -26,3 +26,14 @@ Description:
> >   		streams can be returned to the available secure streams pool by
> >   		invoking the tsm/disconnect flow. The link points to the
> >   		endpoint PCI device at domain:DDDDD bus:BB device:DD function:F.
> > +
> > +What:		pciDDDDD:BB/available_secure_streams
> > +Date:		December, 2024
> > +Contact:	linux-pci@vger.kernel.org
> > +Description:
> > +		(RO) When a host-bridge has root ports that support PCIe IDE
> > +		(link encryption and integrity protection) there may be a
> > +		limited number of streams that can be used for establishing new
> > +		secure links. This attribute decrements upon secure link setup,
> > +		and increments upon secure link teardown. The in-use stream
> > +		count is determined by counting stream symlinks.
> > diff --git a/drivers/pci/ide.c b/drivers/pci/ide.c
> > index c37f35f0d2c0..0abc19b341ab 100644
> > --- a/drivers/pci/ide.c
> > +++ b/drivers/pci/ide.c
> > @@ -75,8 +75,54 @@ void pci_ide_init(struct pci_dev *pdev)
> >   	pdev->nr_ide_mem = nr_ide_mem;
> >   }
> >   
> > +static ssize_t available_secure_streams_show(struct device *dev,
> > +					     struct device_attribute *attr,
> > +					     char *buf)
> > +{
> > +	struct pci_host_bridge *hb = to_pci_host_bridge(dev);
> > +	int avail;
> > +
> > +	if (hb->nr_ide_streams < 0)
> > +		return -ENXIO;
> > +
> > +	avail = hb->nr_ide_streams -
> > +		bitmap_weight(hb->ide_stream_ids, PCI_IDE_SEL_CTL_ID_MAX + 1);
> > +	return sysfs_emit(buf, "%d\n", avail);
> > +}
> > +static DEVICE_ATTR_RO(available_secure_streams);
> > +
> > +static struct attribute *pci_ide_attrs[] = {
> > +	&dev_attr_available_secure_streams.attr,
> > +	NULL,
> > +};
> > +
> > +static umode_t pci_ide_attr_visible(struct kobject *kobj, struct attribute *a, int n)
> > +{
> > +	struct device *dev = kobj_to_dev(kobj);
> > +	struct pci_host_bridge *hb = to_pci_host_bridge(dev);
> > +
> > +	if (a == &dev_attr_available_secure_streams.attr)
> > +		if (hb->nr_ide_streams < 0)
> > +			return 0;
> > +
> > +	return a->mode;
> > +}
> > +
> > +struct attribute_group pci_ide_attr_group = {
> > +	.attrs = pci_ide_attrs,
> > +	.is_visible = pci_ide_attr_visible,
> > +};
> > +
> > +void pci_set_nr_ide_streams(struct pci_host_bridge *hb, int nr)
> > +{
> > +	hb->nr_ide_streams = nr;
> > +	sysfs_update_group(&hb->dev.kobj, &pci_ide_attr_group);
> > +}
> > +EXPORT_SYMBOL_NS_GPL(pci_set_nr_ide_streams, PCI_IDE);
> 
> PCI_IDE needs quotes but somehow it was compiling for months until I 
> rebased onto v6.14.

Oh, interesting, will fix that up when sending v2 based on v6.14-rc.


> Hm. Also probably all exports should be PCI_IDE NS, 
> or none. Thanks,

I will add a comment for why this one is namespaced and the others are
not. I am also renaming it to pci_ide_init_nr_streams() to reflect this
detail:

/**
 * pci_init_nr_ide_streams() - size the pool of IDE Stream resources
 * @hb: host bridge boundary for the stream pool
 * @nr: number of streams
 *
 * Enable IDE Stream establishment by setting the number of stream
 * resources available at the host bridge. Platform init code must set
 * this before the first pci_ide_stream_alloc() call.
 *
 * The "PCI_IDE" symbol namespace is required because this is typically
 * a detail that is settled in early PCI init, i.e. only an expert or
 * test module should consume this export.
 */