[PATCH 0/3] Add parameter for disabling ACS redirection for P2P

[PATCH 0/3] Add parameter for disabling ACS redirection for P2P

[Logan Gunthorpe]

Hi,

As discussed in our PCI P2PDMA series, we'd like to add a kernel
parameter for selectively disabling ACS redirection for select
bridges. Seeing this turned out to be a small series in itself, we've
decided to send this separately from the P2P work.

This series generalizes the code already done for the resource_alignment
option that already exists. The first patch creates a helper function
to match PCI devices against strings based on the code that already
existed in pci_specified_resource_alignment().

The second patch expands the new helper to optionally take a path of
PCI devfns. This is to address Alex's renumbering concern when using
simple bus-devfns. The implementation is essentially how he described it and
similar to the Intel VT-d spec (Section 8.3.1).

The final patch adds the disable_acs_redir kernel parameter which takes
a list of PCI devices and will disable the ACS P2P Request Redirect,
ACS P2P Completion Redirect and ACS P2P Egress Control bits for the
selected devices. This allows P2P traffic between selected bridges and
seeing it's done at boot, before IOMMU group creating the IOMMU groups
will be created correctly based on the bits.

Thanks,

Logan

--

Changes since v1:

* Reworked pci_dev_str_match_path using strrchr as suggested by Alex
* Collected Christian's Acks

--

Logan Gunthorpe (3):
  PCI: Make specifying PCI devices in kernel parameters reusable
  PCI: Allow specifying devices using a base bus and path of devfns
  PCI: Introduce the disable_acs_redir parameter

 Documentation/admin-guide/kernel-parameters.txt |  39 ++-
 drivers/pci/pci.c                               | 353 ++++++++++++++++++++----
 2 files changed, 331 insertions(+), 61 deletions(-)

--
2.11.0

[PATCH 0/3] Add parameter for disabling ACS redirection for P2P

[Logan Gunthorpe]

Hi,

As discussed in our PCI P2PDMA series, we'd like to add a kernel
parameter for selectively disabling ACS redirection for select
bridges. Seeing this turned out to be a small series in itself, we've
decided to send this separately from the P2P work.

This series generalizes the code already done for the resource_alignment
option that already exists. The first patch creates a helper function
to match PCI devices against strings based on the code that already
existed in pci_specified_resource_alignment().

The second patch expands the new helper to optionally take a path of
PCI devfns. This is to address Alex's renumbering concern when using
simple bus-devfns. The implementation is essentially how he described it and
similar to the Intel VT-d spec (Section 8.3.1).

The final patch adds the disable_acs_redir kernel parameter which takes
a list of PCI devices and will disable the ACS P2P Request Redirect,
ACS P2P Completion Redirect and ACS P2P Egress Control bits for the
selected devices. This allows P2P traffic between selected bridges and
seeing it's done at boot, before IOMMU group creating the IOMMU groups
will be created correctly based on the bits.

Thanks,

Logan

--

Changes since v1:

* Reworked pci_dev_str_match_path using strrchr as suggested by Alex
* Collected Christian's Acks

--

Logan Gunthorpe (3):
  PCI: Make specifying PCI devices in kernel parameters reusable
  PCI: Allow specifying devices using a base bus and path of devfns
  PCI: Introduce the disable_acs_redir parameter

 Documentation/admin-guide/kernel-parameters.txt |  39 ++-
 drivers/pci/pci.c                               | 353 ++++++++++++++++++++----
 2 files changed, 331 insertions(+), 61 deletions(-)

--
2.11.0
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[PATCH v2 1/3] PCI: Make specifying PCI devices in kernel parameters reusable

[Logan Gunthorpe]

Separate out the code to match a PCI device with a string (typically
originating from a kernel parameter) from the
pci_specified_resource_alignment() function into its own helper
function.

While we are at it, this change fixes the kernel style of the function
(fixing a number of long lines and extra parentheses).

Additionally, make the analogous change to the kernel parameter
documentation: Separating the description of how to specify a PCI device
into it's own section at the head of the pci= parameter.

Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Reviewed-by: Stephen Bates <sbates@raithlin.com>
Acked-by: Christian König <christian.koenig@amd.com>
---
 Documentation/admin-guide/kernel-parameters.txt |  26 +++-
 drivers/pci/pci.c                               | 153 +++++++++++++++---------
 2 files changed, 120 insertions(+), 59 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index f2040d46f095..e58cc671ff92 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2985,7 +2985,24 @@
 			See header of drivers/block/paride/pcd.c.
 			See also Documentation/blockdev/paride.txt.
 
-	pci=option[,option...]	[PCI] various PCI subsystem options:
+	pci=option[,option...]	[PCI] various PCI subsystem options.
+
+				Some options herein operate on a specific device
+				or a set of devices (<pci_dev>). These are
+				specified in one of two formats:
+
+				[<domain>:]<bus>:<slot>.<func>
+				pci:<vendor>:<device>[:<subvendor>:<subdevice>]
+
+				Note: the first format specifies a PCI
+				bus/slot/function address which may change
+				if new hardware is inserted, if motherboard
+				firmware changes, or due to changes caused
+				by other kernel parameters. The second format
+				selects devices using IDs from the
+				configuration space which may match multiple
+				devices in the system.
+
 		earlydump	[X86] dump PCI config space before the kernel
 			        changes anything
 		off		[X86] don't probe for the PCI bus
@@ -3114,11 +3131,10 @@
 				window. The default value is 64 megabytes.
 		resource_alignment=
 				Format:
-				[<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
-				[<order of align>@]pci:<vendor>:<device>\
-						[:<subvendor>:<subdevice>][; ...]
+				[<order of align>@]<pci_dev>[; ...]
 				Specifies alignment and device to reassign
-				aligned memory resources.
+				aligned memory resources. How to
+				specify the device is described above.
 				If <order of align> is not specified,
 				PAGE_SIZE is used as alignment.
 				PCI-PCI bridge can be specified, if resource
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index dbfe7c4f3776..85fec5e2640b 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -183,6 +183,88 @@ void __iomem *pci_ioremap_wc_bar(struct pci_dev *pdev, int bar)
 EXPORT_SYMBOL_GPL(pci_ioremap_wc_bar);
 #endif
 
+/**
+ * pci_dev_str_match - test if a string matches a device
+ * @dev:    the PCI device to test
+ * @p:      string to match the device against
+ * @endptr: pointer to the string after the match
+ *
+ * Test if a string (typically from a kernel parameter) matches a
+ * specified. The string may be of one of two forms formats:
+ *
+ *   [<domain>:]<bus>:<slot>.<func>
+ *   pci:<vendor>:<device>[:<subvendor>:<subdevice>]
+ *
+ * The first format specifies a PCI bus/slot/function address which
+ * may change if new hardware is inserted, if motherboard firmware changes,
+ * or due to changes caused in kernel parameters.
+ *
+ * The second format matches devices using IDs in the configuration
+ * space which may match multiple devices in the system. A value of 0
+ * for any field will match all devices.
+ *
+ * Returns 1 if the string matches the device, 0 if it does not and
+ * a negative error code if the string cannot be parsed.
+ */
+static int pci_dev_str_match(struct pci_dev *dev, const char *p,
+			     const char **endptr)
+{
+	int ret;
+	int seg, bus, slot, func, count;
+	unsigned short vendor, device, subsystem_vendor, subsystem_device;
+
+	if (strncmp(p, "pci:", 4) == 0) {
+		/* PCI vendor/device (subvendor/subdevice) ids are specified */
+		p += 4;
+		ret = sscanf(p, "%hx:%hx:%hx:%hx%n", &vendor, &device,
+			     &subsystem_vendor, &subsystem_device, &count);
+		if (ret != 4) {
+			ret = sscanf(p, "%hx:%hx%n", &vendor, &device, &count);
+			if (ret != 2)
+				return -EINVAL;
+
+			subsystem_vendor = 0;
+			subsystem_device = 0;
+		}
+
+		p += count;
+
+		if ((!vendor || vendor == dev->vendor) &&
+		    (!device || device == dev->device) &&
+		    (!subsystem_vendor ||
+			    subsystem_vendor == dev->subsystem_vendor) &&
+		    (!subsystem_device ||
+			    subsystem_device == dev->subsystem_device))
+			goto found;
+
+	} else {
+		/* PCI Bus,Slot,Function ids are specified */
+		ret = sscanf(p, "%x:%x:%x.%x%n", &seg, &bus, &slot,
+			     &func, &count);
+		if (ret != 4) {
+			seg = 0;
+			ret = sscanf(p, "%x:%x.%x%n", &bus, &slot,
+				     &func, &count);
+			if (ret != 3)
+				return -EINVAL;
+		}
+
+		p += count;
+
+		if (seg == pci_domain_nr(dev->bus) &&
+		    bus == dev->bus->number &&
+		    slot == PCI_SLOT(dev->devfn) &&
+		    func == PCI_FUNC(dev->devfn))
+			goto found;
+	}
+
+	*endptr = p;
+	return 0;
+
+found:
+	*endptr = p;
+	return 1;
+}
 
 static int __pci_find_next_cap_ttl(struct pci_bus *bus, unsigned int devfn,
 				   u8 pos, int cap, int *ttl)
@@ -5462,10 +5544,10 @@ static DEFINE_SPINLOCK(resource_alignment_lock);
 static resource_size_t pci_specified_resource_alignment(struct pci_dev *dev,
 							bool *resize)
 {
-	int seg, bus, slot, func, align_order, count;
-	unsigned short vendor, device, subsystem_vendor, subsystem_device;
+	int align_order, count;
 	resource_size_t align = pcibios_default_alignment();
-	char *p;
+	const char *p;
+	int ret;
 
 	spin_lock(&resource_alignment_lock);
 	p = resource_alignment_param;
@@ -5485,58 +5567,21 @@ static resource_size_t pci_specified_resource_alignment(struct pci_dev *dev,
 		} else {
 			align_order = -1;
 		}
-		if (strncmp(p, "pci:", 4) == 0) {
-			/* PCI vendor/device (subvendor/subdevice) ids are specified */
-			p += 4;
-			if (sscanf(p, "%hx:%hx:%hx:%hx%n",
-				&vendor, &device, &subsystem_vendor, &subsystem_device, &count) != 4) {
-				if (sscanf(p, "%hx:%hx%n", &vendor, &device, &count) != 2) {
-					printk(KERN_ERR "PCI: Can't parse resource_alignment parameter: pci:%s\n",
-						p);
-					break;
-				}
-				subsystem_vendor = subsystem_device = 0;
-			}
-			p += count;
-			if ((!vendor || (vendor == dev->vendor)) &&
-				(!device || (device == dev->device)) &&
-				(!subsystem_vendor || (subsystem_vendor == dev->subsystem_vendor)) &&
-				(!subsystem_device || (subsystem_device == dev->subsystem_device))) {
-				*resize = true;
-				if (align_order == -1)
-					align = PAGE_SIZE;
-				else
-					align = 1 << align_order;
-				/* Found */
-				break;
-			}
-		}
-		else {
-			if (sscanf(p, "%x:%x:%x.%x%n",
-				&seg, &bus, &slot, &func, &count) != 4) {
-				seg = 0;
-				if (sscanf(p, "%x:%x.%x%n",
-						&bus, &slot, &func, &count) != 3) {
-					/* Invalid format */
-					printk(KERN_ERR "PCI: Can't parse resource_alignment parameter: %s\n",
-						p);
-					break;
-				}
-			}
-			p += count;
-			if (seg == pci_domain_nr(dev->bus) &&
-				bus == dev->bus->number &&
-				slot == PCI_SLOT(dev->devfn) &&
-				func == PCI_FUNC(dev->devfn)) {
-				*resize = true;
-				if (align_order == -1)
-					align = PAGE_SIZE;
-				else
-					align = 1 << align_order;
-				/* Found */
-				break;
-			}
+
+		ret = pci_dev_str_match(dev, p, &p);
+		if (ret == 1) {
+			*resize = true;
+			if (align_order == -1)
+				align = PAGE_SIZE;
+			else
+				align = 1 << align_order;
+			break;
+		} else if (ret < 0) {
+			pr_info("PCI: Can't parse resource_alignment parameter: pci:%s\n",
+				p);
+			break;
 		}
+
 		if (*p != ';' && *p != ',') {
 			/* End of param or invalid format */
 			break;
-- 
2.11.0

[PATCH v2 1/3] PCI: Make specifying PCI devices in kernel parameters reusable

[Logan Gunthorpe]

Separate out the code to match a PCI device with a string (typically
originating from a kernel parameter) from the
pci_specified_resource_alignment() function into its own helper
function.

While we are at it, this change fixes the kernel style of the function
(fixing a number of long lines and extra parentheses).

Additionally, make the analogous change to the kernel parameter
documentation: Separating the description of how to specify a PCI device
into it's own section at the head of the pci= parameter.

Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Reviewed-by: Stephen Bates <sbates@raithlin.com>
Acked-by: Christian König <christian.koenig@amd.com>
---
 Documentation/admin-guide/kernel-parameters.txt |  26 +++-
 drivers/pci/pci.c                               | 153 +++++++++++++++---------
 2 files changed, 120 insertions(+), 59 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index f2040d46f095..e58cc671ff92 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2985,7 +2985,24 @@
 			See header of drivers/block/paride/pcd.c.
 			See also Documentation/blockdev/paride.txt.
 
-	pci=option[,option...]	[PCI] various PCI subsystem options:
+	pci=option[,option...]	[PCI] various PCI subsystem options.
+
+				Some options herein operate on a specific device
+				or a set of devices (<pci_dev>). These are
+				specified in one of two formats:
+
+				[<domain>:]<bus>:<slot>.<func>
+				pci:<vendor>:<device>[:<subvendor>:<subdevice>]
+
+				Note: the first format specifies a PCI
+				bus/slot/function address which may change
+				if new hardware is inserted, if motherboard
+				firmware changes, or due to changes caused
+				by other kernel parameters. The second format
+				selects devices using IDs from the
+				configuration space which may match multiple
+				devices in the system.
+
 		earlydump	[X86] dump PCI config space before the kernel
 			        changes anything
 		off		[X86] don't probe for the PCI bus
@@ -3114,11 +3131,10 @@
 				window. The default value is 64 megabytes.
 		resource_alignment=
 				Format:
-				[<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
-				[<order of align>@]pci:<vendor>:<device>\
-						[:<subvendor>:<subdevice>][; ...]
+				[<order of align>@]<pci_dev>[; ...]
 				Specifies alignment and device to reassign
-				aligned memory resources.
+				aligned memory resources. How to
+				specify the device is described above.
 				If <order of align> is not specified,
 				PAGE_SIZE is used as alignment.
 				PCI-PCI bridge can be specified, if resource
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index dbfe7c4f3776..85fec5e2640b 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -183,6 +183,88 @@ void __iomem *pci_ioremap_wc_bar(struct pci_dev *pdev, int bar)
 EXPORT_SYMBOL_GPL(pci_ioremap_wc_bar);
 #endif
 
+/**
+ * pci_dev_str_match - test if a string matches a device
+ * @dev:    the PCI device to test
+ * @p:      string to match the device against
+ * @endptr: pointer to the string after the match
+ *
+ * Test if a string (typically from a kernel parameter) matches a
+ * specified. The string may be of one of two forms formats:
+ *
+ *   [<domain>:]<bus>:<slot>.<func>
+ *   pci:<vendor>:<device>[:<subvendor>:<subdevice>]
+ *
+ * The first format specifies a PCI bus/slot/function address which
+ * may change if new hardware is inserted, if motherboard firmware changes,
+ * or due to changes caused in kernel parameters.
+ *
+ * The second format matches devices using IDs in the configuration
+ * space which may match multiple devices in the system. A value of 0
+ * for any field will match all devices.
+ *
+ * Returns 1 if the string matches the device, 0 if it does not and
+ * a negative error code if the string cannot be parsed.
+ */
+static int pci_dev_str_match(struct pci_dev *dev, const char *p,
+			     const char **endptr)
+{
+	int ret;
+	int seg, bus, slot, func, count;
+	unsigned short vendor, device, subsystem_vendor, subsystem_device;
+
+	if (strncmp(p, "pci:", 4) == 0) {
+		/* PCI vendor/device (subvendor/subdevice) ids are specified */
+		p += 4;
+		ret = sscanf(p, "%hx:%hx:%hx:%hx%n", &vendor, &device,
+			     &subsystem_vendor, &subsystem_device, &count);
+		if (ret != 4) {
+			ret = sscanf(p, "%hx:%hx%n", &vendor, &device, &count);
+			if (ret != 2)
+				return -EINVAL;
+
+			subsystem_vendor = 0;
+			subsystem_device = 0;
+		}
+
+		p += count;
+
+		if ((!vendor || vendor == dev->vendor) &&
+		    (!device || device == dev->device) &&
+		    (!subsystem_vendor ||
+			    subsystem_vendor == dev->subsystem_vendor) &&
+		    (!subsystem_device ||
+			    subsystem_device == dev->subsystem_device))
+			goto found;
+
+	} else {
+		/* PCI Bus,Slot,Function ids are specified */
+		ret = sscanf(p, "%x:%x:%x.%x%n", &seg, &bus, &slot,
+			     &func, &count);
+		if (ret != 4) {
+			seg = 0;
+			ret = sscanf(p, "%x:%x.%x%n", &bus, &slot,
+				     &func, &count);
+			if (ret != 3)
+				return -EINVAL;
+		}
+
+		p += count;
+
+		if (seg == pci_domain_nr(dev->bus) &&
+		    bus == dev->bus->number &&
+		    slot == PCI_SLOT(dev->devfn) &&
+		    func == PCI_FUNC(dev->devfn))
+			goto found;
+	}
+
+	*endptr = p;
+	return 0;
+
+found:
+	*endptr = p;
+	return 1;
+}
 
 static int __pci_find_next_cap_ttl(struct pci_bus *bus, unsigned int devfn,
 				   u8 pos, int cap, int *ttl)
@@ -5462,10 +5544,10 @@ static DEFINE_SPINLOCK(resource_alignment_lock);
 static resource_size_t pci_specified_resource_alignment(struct pci_dev *dev,
 							bool *resize)
 {
-	int seg, bus, slot, func, align_order, count;
-	unsigned short vendor, device, subsystem_vendor, subsystem_device;
+	int align_order, count;
 	resource_size_t align = pcibios_default_alignment();
-	char *p;
+	const char *p;
+	int ret;
 
 	spin_lock(&resource_alignment_lock);
 	p = resource_alignment_param;
@@ -5485,58 +5567,21 @@ static resource_size_t pci_specified_resource_alignment(struct pci_dev *dev,
 		} else {
 			align_order = -1;
 		}
-		if (strncmp(p, "pci:", 4) == 0) {
-			/* PCI vendor/device (subvendor/subdevice) ids are specified */
-			p += 4;
-			if (sscanf(p, "%hx:%hx:%hx:%hx%n",
-				&vendor, &device, &subsystem_vendor, &subsystem_device, &count) != 4) {
-				if (sscanf(p, "%hx:%hx%n", &vendor, &device, &count) != 2) {
-					printk(KERN_ERR "PCI: Can't parse resource_alignment parameter: pci:%s\n",
-						p);
-					break;
-				}
-				subsystem_vendor = subsystem_device = 0;
-			}
-			p += count;
-			if ((!vendor || (vendor == dev->vendor)) &&
-				(!device || (device == dev->device)) &&
-				(!subsystem_vendor || (subsystem_vendor == dev->subsystem_vendor)) &&
-				(!subsystem_device || (subsystem_device == dev->subsystem_device))) {
-				*resize = true;
-				if (align_order == -1)
-					align = PAGE_SIZE;
-				else
-					align = 1 << align_order;
-				/* Found */
-				break;
-			}
-		}
-		else {
-			if (sscanf(p, "%x:%x:%x.%x%n",
-				&seg, &bus, &slot, &func, &count) != 4) {
-				seg = 0;
-				if (sscanf(p, "%x:%x.%x%n",
-						&bus, &slot, &func, &count) != 3) {
-					/* Invalid format */
-					printk(KERN_ERR "PCI: Can't parse resource_alignment parameter: %s\n",
-						p);
-					break;
-				}
-			}
-			p += count;
-			if (seg == pci_domain_nr(dev->bus) &&
-				bus == dev->bus->number &&
-				slot == PCI_SLOT(dev->devfn) &&
-				func == PCI_FUNC(dev->devfn)) {
-				*resize = true;
-				if (align_order == -1)
-					align = PAGE_SIZE;
-				else
-					align = 1 << align_order;
-				/* Found */
-				break;
-			}
+
+		ret = pci_dev_str_match(dev, p, &p);
+		if (ret == 1) {
+			*resize = true;
+			if (align_order == -1)
+				align = PAGE_SIZE;
+			else
+				align = 1 << align_order;
+			break;
+		} else if (ret < 0) {
+			pr_info("PCI: Can't parse resource_alignment parameter: pci:%s\n",
+				p);
+			break;
 		}
+
 		if (*p != ';' && *p != ',') {
 			/* End of param or invalid format */
 			break;
-- 
2.11.0

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Re: [PATCH v2 1/3] PCI: Make specifying PCI devices in kernel parameters reusable

[Andy Shevchenko]

On Fri, Jun 1, 2018 at 2:50 AM, Logan Gunthorpe <logang@deltatee.com> wrote:
> Separate out the code to match a PCI device with a string (typically
> originating from a kernel parameter) from the
> pci_specified_resource_alignment() function into its own helper
> function.
>
> While we are at it, this change fixes the kernel style of the function
> (fixing a number of long lines and extra parentheses).
>
> Additionally, make the analogous change to the kernel parameter
> documentation: Separating the description of how to specify a PCI device
> into it's own section at the head of the pci= parameter.
>
> Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
> Reviewed-by: Stephen Bates <sbates@raithlin.com>
> Acked-by: Christian König <christian.koenig@amd.com>

Sorry for maybe being late here.

> -       pci=option[,option...]  [PCI] various PCI subsystem options:
> +       pci=option[,option...]  [PCI] various PCI subsystem options.
> +
> +                               Some options herein operate on a specific device
> +                               or a set of devices (<pci_dev>). These are
> +                               specified in one of two formats:

I would rather to add

 <pci_dev>

here in the same way as done for options.
It would be easy for people to find a referenced paragraph.

> +
> +                               [<domain>:]<bus>:<slot>.<func>
> +                               pci:<vendor>:<device>[:<subvendor>:<subdevice>]
> +
> +                               Note: the first format specifies a PCI
> +                               bus/slot/function address which may change
> +                               if new hardware is inserted, if motherboard
> +                               firmware changes, or due to changes caused
> +                               by other kernel parameters. The second format
> +                               selects devices using IDs from the
> +                               configuration space which may match multiple
> +                               devices in the system.

> +static int pci_dev_str_match(struct pci_dev *dev, const char *p,
> +                            const char **endptr)

This change I hope has no functional alteration, so, can be split to a
separate patch.

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v2 1/3] PCI: Make specifying PCI devices in kernel parameters reusable

[Andy Shevchenko]

On Fri, Jun 1, 2018 at 2:50 AM, Logan Gunthorpe <logang@deltatee.com> wrote=
:
> Separate out the code to match a PCI device with a string (typically
> originating from a kernel parameter) from the
> pci_specified_resource_alignment() function into its own helper
> function.
>
> While we are at it, this change fixes the kernel style of the function
> (fixing a number of long lines and extra parentheses).
>
> Additionally, make the analogous change to the kernel parameter
> documentation: Separating the description of how to specify a PCI device
> into it's own section at the head of the pci=3D parameter.
>
> Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
> Reviewed-by: Stephen Bates <sbates@raithlin.com>
> Acked-by: Christian K=C3=B6nig <christian.koenig@amd.com>

Sorry for maybe being late here.

> -       pci=3Doption[,option...]  [PCI] various PCI subsystem options:
> +       pci=3Doption[,option...]  [PCI] various PCI subsystem options.
> +
> +                               Some options herein operate on a specific=
 device
> +                               or a set of devices (<pci_dev>). These ar=
e
> +                               specified in one of two formats:

I would rather to add

 <pci_dev>

here in the same way as done for options.
It would be easy for people to find a referenced paragraph.

> +
> +                               [<domain>:]<bus>:<slot>.<func>
> +                               pci:<vendor>:<device>[:<subvendor>:<subde=
vice>]
> +
> +                               Note: the first format specifies a PCI
> +                               bus/slot/function address which may chang=
e
> +                               if new hardware is inserted, if motherboa=
rd
> +                               firmware changes, or due to changes cause=
d
> +                               by other kernel parameters. The second fo=
rmat
> +                               selects devices using IDs from the
> +                               configuration space which may match multi=
ple
> +                               devices in the system.

> +static int pci_dev_str_match(struct pci_dev *dev, const char *p,
> +                            const char **endptr)

This change I hope has no functional alteration, so, can be split to a
separate patch.

--=20
With Best Regards,
Andy Shevchenko

Re: [PATCH v2 1/3] PCI: Make specifying PCI devices in kernel parameters reusable

[Andy Shevchenko]

On Fri, Jun 1, 2018 at 2:50 AM, Logan Gunthorpe <logang@deltatee.com> wrote:
> Separate out the code to match a PCI device with a string (typically
> originating from a kernel parameter) from the
> pci_specified_resource_alignment() function into its own helper
> function.
>
> While we are at it, this change fixes the kernel style of the function
> (fixing a number of long lines and extra parentheses).
>
> Additionally, make the analogous change to the kernel parameter
> documentation: Separating the description of how to specify a PCI device
> into it's own section at the head of the pci= parameter.
>
> Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
> Reviewed-by: Stephen Bates <sbates@raithlin.com>
> Acked-by: Christian König <christian.koenig@amd.com>

Sorry for maybe being late here.

> -       pci=option[,option...]  [PCI] various PCI subsystem options:
> +       pci=option[,option...]  [PCI] various PCI subsystem options.
> +
> +                               Some options herein operate on a specific device
> +                               or a set of devices (<pci_dev>). These are
> +                               specified in one of two formats:

I would rather to add

 <pci_dev>

here in the same way as done for options.
It would be easy for people to find a referenced paragraph.

> +
> +                               [<domain>:]<bus>:<slot>.<func>
> +                               pci:<vendor>:<device>[:<subvendor>:<subdevice>]
> +
> +                               Note: the first format specifies a PCI
> +                               bus/slot/function address which may change
> +                               if new hardware is inserted, if motherboard
> +                               firmware changes, or due to changes caused
> +                               by other kernel parameters. The second format
> +                               selects devices using IDs from the
> +                               configuration space which may match multiple
> +                               devices in the system.

> +static int pci_dev_str_match(struct pci_dev *dev, const char *p,
> +                            const char **endptr)

This change I hope has no functional alteration, so, can be split to a
separate patch.

-- 
With Best Regards,
Andy Shevchenko
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Re: [PATCH v2 1/3] PCI: Make specifying PCI devices in kernel parameters reusable

[Logan Gunthorpe]

On 01/06/18 04:39 AM, Andy Shevchenko wrote:
>> -       pci=option[,option...]  [PCI] various PCI subsystem options:
>> +       pci=option[,option...]  [PCI] various PCI subsystem options.
>> +
>> +                               Some options herein operate on a specific device
>> +                               or a set of devices (<pci_dev>). These are
>> +                               specified in one of two formats:
> 
> I would rather to add
> 
>  <pci_dev>
> 
> here in the same way as done for options.
> It would be easy for people to find a referenced paragraph.

Sorry, I don't understand what you are asking. Can you be more specific?

>> +
>> +                               [<domain>:]<bus>:<slot>.<func>
>> +                               pci:<vendor>:<device>[:<subvendor>:<subdevice>]
>> +
>> +                               Note: the first format specifies a PCI
>> +                               bus/slot/function address which may change
>> +                               if new hardware is inserted, if motherboard
>> +                               firmware changes, or due to changes caused
>> +                               by other kernel parameters. The second format
>> +                               selects devices using IDs from the
>> +                               configuration space which may match multiple
>> +                               devices in the system.
> 
>> +static int pci_dev_str_match(struct pci_dev *dev, const char *p,
>> +                            const char **endptr)
> 
> This change I hope has no functional alteration, so, can be split to a
> separate patch.

That's all this patch does... Or do you want be to separate out
documentation from implementation? That just seems a bit excessive to me.

Logan

Re: [PATCH v2 1/3] PCI: Make specifying PCI devices in kernel parameters reusable

[Logan Gunthorpe]

On 01/06/18 04:39 AM, Andy Shevchenko wrote:
>> -       pci=option[,option...]  [PCI] various PCI subsystem options:
>> +       pci=option[,option...]  [PCI] various PCI subsystem options.
>> +
>> +                               Some options herein operate on a specific device
>> +                               or a set of devices (<pci_dev>). These are
>> +                               specified in one of two formats:
> 
> I would rather to add
> 
>  <pci_dev>
> 
> here in the same way as done for options.
> It would be easy for people to find a referenced paragraph.

Sorry, I don't understand what you are asking. Can you be more specific?

>> +
>> +                               [<domain>:]<bus>:<slot>.<func>
>> +                               pci:<vendor>:<device>[:<subvendor>:<subdevice>]
>> +
>> +                               Note: the first format specifies a PCI
>> +                               bus/slot/function address which may change
>> +                               if new hardware is inserted, if motherboard
>> +                               firmware changes, or due to changes caused
>> +                               by other kernel parameters. The second format
>> +                               selects devices using IDs from the
>> +                               configuration space which may match multiple
>> +                               devices in the system.
> 
>> +static int pci_dev_str_match(struct pci_dev *dev, const char *p,
>> +                            const char **endptr)
> 
> This change I hope has no functional alteration, so, can be split to a
> separate patch.

That's all this patch does... Or do you want be to separate out
documentation from implementation? That just seems a bit excessive to me.

Logan
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[PATCH v2 2/3] PCI: Allow specifying devices using a base bus and path of devfns

[Logan Gunthorpe]

When specifying PCI devices on the kernel command line using a
BDF, the bus numbers can change when adding or replacing a device,
changing motherboard firmware, or applying kernel parameters like
pci=assign-buses. When this happens, it is usually undesirable to
apply whatever command line tweak to the wrong device.

Therefore, it is useful to be able to specify devices with a base
bus number and the path of devfns needed to get to it. (Similar to
the "device scope" structure in the Intel VT-d spec, Section 8.3.1.)

Thus, we add an option to specify devices in the following format:

path:[<domain>:]<bus>:<slot>.<func>/<slot>.<func>[/ ...]

The path can be any segment within the PCI hierarchy of any length and
determined through the use of 'lspci -t'. When specified this way, it is
less likely that a renumbered bus will result in a valid device specification
and the tweak won't be applied to the wrong device.

Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Reviewed-by: Stephen Bates <sbates@raithlin.com>
Acked-by: Christian König <christian.koenig@amd.com>
---
 Documentation/admin-guide/kernel-parameters.txt |  12 ++-
 drivers/pci/pci.c                               | 101 +++++++++++++++++++++++-
 2 files changed, 107 insertions(+), 6 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index e58cc671ff92..bc51b316f485 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2989,9 +2989,10 @@
 
 				Some options herein operate on a specific device
 				or a set of devices (<pci_dev>). These are
-				specified in one of two formats:
+				specified in one of three formats:
 
 				[<domain>:]<bus>:<slot>.<func>
+				path:[<domain>:]<bus>:<slot>.<func>/<slot>.<func>[/ ...]
 				pci:<vendor>:<device>[:<subvendor>:<subdevice>]
 
 				Note: the first format specifies a PCI
@@ -2999,9 +3000,12 @@
 				if new hardware is inserted, if motherboard
 				firmware changes, or due to changes caused
 				by other kernel parameters. The second format
-				selects devices using IDs from the
-				configuration space which may match multiple
-				devices in the system.
+				specifies a path from a device through
+				a path of multiple slot/function addresses
+				(this is more robust against renumbering
+				issues). The third format selects devices using
+				IDs from the configuration space which may match
+				multiple devices in the system.
 
 		earlydump	[X86] dump PCI config space before the kernel
 			        changes anything
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 85fec5e2640b..39f11bd0ee03 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -184,22 +184,111 @@ EXPORT_SYMBOL_GPL(pci_ioremap_wc_bar);
 #endif
 
 /**
+ * pci_dev_str_match_path - test if a path string matches a device
+ * @dev:    the PCI device to test
+ * @p:      string to match the device against
+ * @endptr: pointer to the string after the match
+ *
+ * Test if a string (typically from a kernel parameter) formated as a
+ * path of slot/function addresses matches a PCI device. The string must
+ * be of the form:
+ *
+ *   [<domain>:]<bus>:<slot>.<func>/<slot>.<func>[/ ...]
+ *
+ * A path for a device can be obtained using 'lspci -t'. Using a path
+ * is more robust against renumbering of devices than using only
+ * a single bus, slot and function address.
+ *
+ * Returns 1 if the string matches the device, 0 if it does not and
+ * a negative error code if it fails to parse the string.
+ */
+static int pci_dev_str_match_path(struct pci_dev *dev, const char *path,
+				  const char **endptr)
+{
+	int ret;
+	int seg, bus, slot, func;
+	char *wpath, *p;
+	char end;
+
+	*endptr = strchrnul(path, ';');
+
+	wpath = kmemdup_nul(path, *endptr - path, GFP_KERNEL);
+	if (!wpath)
+		return -ENOMEM;
+
+	while (1) {
+		p = strrchr(wpath, '/');
+		if (!p)
+			break;
+		ret = sscanf(p, "/%x.%x%c", &slot, &func, &end);
+		if (ret != 2) {
+			ret = -EINVAL;
+			goto free_and_exit;
+		}
+
+		if (dev->devfn != PCI_DEVFN(slot, func)) {
+			ret = 0;
+			goto free_and_exit;
+		}
+
+		/*
+		 * Note: we don't need to get a reference to the upstream
+		 * bridge because we hold a reference to the top level
+		 * device which should hold a reference to the bridge,
+		 * and so on.
+		 */
+		dev = pci_upstream_bridge(dev);
+		if (!dev) {
+			ret = 0;
+			goto free_and_exit;
+		}
+
+		*p = 0;
+	}
+
+	ret = sscanf(wpath, "%x:%x:%x.%x%c", &seg, &bus, &slot,
+		     &func, &end);
+	if (ret != 4) {
+		seg = 0;
+		ret = sscanf(wpath, "%x:%x.%x%c", &bus, &slot, &func, &end);
+		if (ret != 3) {
+			ret = -EINVAL;
+			goto free_and_exit;
+		}
+	}
+
+	ret = (seg == pci_domain_nr(dev->bus) &&
+	       bus == dev->bus->number &&
+	       dev->devfn == PCI_DEVFN(slot, func));
+
+free_and_exit:
+	kfree(wpath);
+	return ret;
+}
+
+/**
  * pci_dev_str_match - test if a string matches a device
  * @dev:    the PCI device to test
  * @p:      string to match the device against
  * @endptr: pointer to the string after the match
  *
  * Test if a string (typically from a kernel parameter) matches a
- * specified. The string may be of one of two forms formats:
+ * specified. The string may be of one of three formats:
  *
  *   [<domain>:]<bus>:<slot>.<func>
+ *   path:[<domain>:]<bus>:<slot>.<func>/<slot>.<func>[/ ...]
  *   pci:<vendor>:<device>[:<subvendor>:<subdevice>]
  *
  * The first format specifies a PCI bus/slot/function address which
  * may change if new hardware is inserted, if motherboard firmware changes,
  * or due to changes caused in kernel parameters.
  *
- * The second format matches devices using IDs in the configuration
+ * The second format specifies a PCI bus/slot/function root address and
+ * a path of slot/function addresses to the specific device from the root.
+ * The path for a device can be determined through the use of 'lspci -t'.
+ * This format is more robust against renumbering issues than the first format.
+
+ * The third format matches devices using IDs in the configuration
  * space which may match multiple devices in the system. A value of 0
  * for any field will match all devices.
  *
@@ -236,7 +325,15 @@ static int pci_dev_str_match(struct pci_dev *dev, const char *p,
 		    (!subsystem_device ||
 			    subsystem_device == dev->subsystem_device))
 			goto found;
+	} else if (strncmp(p, "path:", 5) == 0) {
+		/* PCI Root Bus and a path of Slot,Function IDs */
+		p += 5;
 
+		ret = pci_dev_str_match_path(dev, p, &p);
+		if (ret < 0)
+			return ret;
+		else if (ret)
+			goto found;
 	} else {
 		/* PCI Bus,Slot,Function ids are specified */
 		ret = sscanf(p, "%x:%x:%x.%x%n", &seg, &bus, &slot,
-- 
2.11.0

[PATCH v2 2/3] PCI: Allow specifying devices using a base bus and path of devfns

[Logan Gunthorpe]

When specifying PCI devices on the kernel command line using a
BDF, the bus numbers can change when adding or replacing a device,
changing motherboard firmware, or applying kernel parameters like
pci=assign-buses. When this happens, it is usually undesirable to
apply whatever command line tweak to the wrong device.

Therefore, it is useful to be able to specify devices with a base
bus number and the path of devfns needed to get to it. (Similar to
the "device scope" structure in the Intel VT-d spec, Section 8.3.1.)

Thus, we add an option to specify devices in the following format:

path:[<domain>:]<bus>:<slot>.<func>/<slot>.<func>[/ ...]

The path can be any segment within the PCI hierarchy of any length and
determined through the use of 'lspci -t'. When specified this way, it is
less likely that a renumbered bus will result in a valid device specification
and the tweak won't be applied to the wrong device.

Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Reviewed-by: Stephen Bates <sbates@raithlin.com>
Acked-by: Christian König <christian.koenig@amd.com>
---
 Documentation/admin-guide/kernel-parameters.txt |  12 ++-
 drivers/pci/pci.c                               | 101 +++++++++++++++++++++++-
 2 files changed, 107 insertions(+), 6 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index e58cc671ff92..bc51b316f485 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2989,9 +2989,10 @@
 
 				Some options herein operate on a specific device
 				or a set of devices (<pci_dev>). These are
-				specified in one of two formats:
+				specified in one of three formats:
 
 				[<domain>:]<bus>:<slot>.<func>
+				path:[<domain>:]<bus>:<slot>.<func>/<slot>.<func>[/ ...]
 				pci:<vendor>:<device>[:<subvendor>:<subdevice>]
 
 				Note: the first format specifies a PCI
@@ -2999,9 +3000,12 @@
 				if new hardware is inserted, if motherboard
 				firmware changes, or due to changes caused
 				by other kernel parameters. The second format
-				selects devices using IDs from the
-				configuration space which may match multiple
-				devices in the system.
+				specifies a path from a device through
+				a path of multiple slot/function addresses
+				(this is more robust against renumbering
+				issues). The third format selects devices using
+				IDs from the configuration space which may match
+				multiple devices in the system.
 
 		earlydump	[X86] dump PCI config space before the kernel
 			        changes anything
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 85fec5e2640b..39f11bd0ee03 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -184,22 +184,111 @@ EXPORT_SYMBOL_GPL(pci_ioremap_wc_bar);
 #endif
 
 /**
+ * pci_dev_str_match_path - test if a path string matches a device
+ * @dev:    the PCI device to test
+ * @p:      string to match the device against
+ * @endptr: pointer to the string after the match
+ *
+ * Test if a string (typically from a kernel parameter) formated as a
+ * path of slot/function addresses matches a PCI device. The string must
+ * be of the form:
+ *
+ *   [<domain>:]<bus>:<slot>.<func>/<slot>.<func>[/ ...]
+ *
+ * A path for a device can be obtained using 'lspci -t'. Using a path
+ * is more robust against renumbering of devices than using only
+ * a single bus, slot and function address.
+ *
+ * Returns 1 if the string matches the device, 0 if it does not and
+ * a negative error code if it fails to parse the string.
+ */
+static int pci_dev_str_match_path(struct pci_dev *dev, const char *path,
+				  const char **endptr)
+{
+	int ret;
+	int seg, bus, slot, func;
+	char *wpath, *p;
+	char end;
+
+	*endptr = strchrnul(path, ';');
+
+	wpath = kmemdup_nul(path, *endptr - path, GFP_KERNEL);
+	if (!wpath)
+		return -ENOMEM;
+
+	while (1) {
+		p = strrchr(wpath, '/');
+		if (!p)
+			break;
+		ret = sscanf(p, "/%x.%x%c", &slot, &func, &end);
+		if (ret != 2) {
+			ret = -EINVAL;
+			goto free_and_exit;
+		}
+
+		if (dev->devfn != PCI_DEVFN(slot, func)) {
+			ret = 0;
+			goto free_and_exit;
+		}
+
+		/*
+		 * Note: we don't need to get a reference to the upstream
+		 * bridge because we hold a reference to the top level
+		 * device which should hold a reference to the bridge,
+		 * and so on.
+		 */
+		dev = pci_upstream_bridge(dev);
+		if (!dev) {
+			ret = 0;
+			goto free_and_exit;
+		}
+
+		*p = 0;
+	}
+
+	ret = sscanf(wpath, "%x:%x:%x.%x%c", &seg, &bus, &slot,
+		     &func, &end);
+	if (ret != 4) {
+		seg = 0;
+		ret = sscanf(wpath, "%x:%x.%x%c", &bus, &slot, &func, &end);
+		if (ret != 3) {
+			ret = -EINVAL;
+			goto free_and_exit;
+		}
+	}
+
+	ret = (seg == pci_domain_nr(dev->bus) &&
+	       bus == dev->bus->number &&
+	       dev->devfn == PCI_DEVFN(slot, func));
+
+free_and_exit:
+	kfree(wpath);
+	return ret;
+}
+
+/**
  * pci_dev_str_match - test if a string matches a device
  * @dev:    the PCI device to test
  * @p:      string to match the device against
  * @endptr: pointer to the string after the match
  *
  * Test if a string (typically from a kernel parameter) matches a
- * specified. The string may be of one of two forms formats:
+ * specified. The string may be of one of three formats:
  *
  *   [<domain>:]<bus>:<slot>.<func>
+ *   path:[<domain>:]<bus>:<slot>.<func>/<slot>.<func>[/ ...]
  *   pci:<vendor>:<device>[:<subvendor>:<subdevice>]
  *
  * The first format specifies a PCI bus/slot/function address which
  * may change if new hardware is inserted, if motherboard firmware changes,
  * or due to changes caused in kernel parameters.
  *
- * The second format matches devices using IDs in the configuration
+ * The second format specifies a PCI bus/slot/function root address and
+ * a path of slot/function addresses to the specific device from the root.
+ * The path for a device can be determined through the use of 'lspci -t'.
+ * This format is more robust against renumbering issues than the first format.
+
+ * The third format matches devices using IDs in the configuration
  * space which may match multiple devices in the system. A value of 0
  * for any field will match all devices.
  *
@@ -236,7 +325,15 @@ static int pci_dev_str_match(struct pci_dev *dev, const char *p,
 		    (!subsystem_device ||
 			    subsystem_device == dev->subsystem_device))
 			goto found;
+	} else if (strncmp(p, "path:", 5) == 0) {
+		/* PCI Root Bus and a path of Slot,Function IDs */
+		p += 5;
 
+		ret = pci_dev_str_match_path(dev, p, &p);
+		if (ret < 0)
+			return ret;
+		else if (ret)
+			goto found;
 	} else {
 		/* PCI Bus,Slot,Function ids are specified */
 		ret = sscanf(p, "%x:%x:%x.%x%n", &seg, &bus, &slot,
-- 
2.11.0

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Re: [PATCH v2 2/3] PCI: Allow specifying devices using a base bus and path of devfns

[Andy Shevchenko]

On Fri, Jun 1, 2018 at 2:50 AM, Logan Gunthorpe <logang@deltatee.com> wrote:
> When specifying PCI devices on the kernel command line using a
> BDF, the bus numbers can change when adding or replacing a device,
> changing motherboard firmware, or applying kernel parameters like
> pci=assign-buses. When this happens, it is usually undesirable to
> apply whatever command line tweak to the wrong device.
>
> Therefore, it is useful to be able to specify devices with a base
> bus number and the path of devfns needed to get to it. (Similar to
> the "device scope" structure in the Intel VT-d spec, Section 8.3.1.)
>
> Thus, we add an option to specify devices in the following format:
>
> path:[<domain>:]<bus>:<slot>.<func>/<slot>.<func>[/ ...]
>
> The path can be any segment within the PCI hierarchy of any length and
> determined through the use of 'lspci -t'. When specified this way, it is
> less likely that a renumbered bus will result in a valid device specification
> and the tweak won't be applied to the wrong device.
>
> Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
> Reviewed-by: Stephen Bates <sbates@raithlin.com>
> Acked-by: Christian König <christian.koenig@amd.com>

> -                               specified in one of two formats:
> +                               specified in one of three formats:

...in one of the following formats:

in the first place and don't fix it each time you add/remove one?


-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v2 2/3] PCI: Allow specifying devices using a base bus and path of devfns

[Andy Shevchenko]

On Fri, Jun 1, 2018 at 2:50 AM, Logan Gunthorpe <logang@deltatee.com> wrote=
:
> When specifying PCI devices on the kernel command line using a
> BDF, the bus numbers can change when adding or replacing a device,
> changing motherboard firmware, or applying kernel parameters like
> pci=3Dassign-buses. When this happens, it is usually undesirable to
> apply whatever command line tweak to the wrong device.
>
> Therefore, it is useful to be able to specify devices with a base
> bus number and the path of devfns needed to get to it. (Similar to
> the "device scope" structure in the Intel VT-d spec, Section 8.3.1.)
>
> Thus, we add an option to specify devices in the following format:
>
> path:[<domain>:]<bus>:<slot>.<func>/<slot>.<func>[/ ...]
>
> The path can be any segment within the PCI hierarchy of any length and
> determined through the use of 'lspci -t'. When specified this way, it is
> less likely that a renumbered bus will result in a valid device specifica=
tion
> and the tweak won't be applied to the wrong device.
>
> Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
> Reviewed-by: Stephen Bates <sbates@raithlin.com>
> Acked-by: Christian K=C3=B6nig <christian.koenig@amd.com>

> -                               specified in one of two formats:
> +                               specified in one of three formats:

...in one of the following formats:

in the first place and don't fix it each time you add/remove one?


--=20
With Best Regards,
Andy Shevchenko

Re: [PATCH v2 2/3] PCI: Allow specifying devices using a base bus and path of devfns

[Andy Shevchenko]

On Fri, Jun 1, 2018 at 2:50 AM, Logan Gunthorpe <logang@deltatee.com> wrote:
> When specifying PCI devices on the kernel command line using a
> BDF, the bus numbers can change when adding or replacing a device,
> changing motherboard firmware, or applying kernel parameters like
> pci=assign-buses. When this happens, it is usually undesirable to
> apply whatever command line tweak to the wrong device.
>
> Therefore, it is useful to be able to specify devices with a base
> bus number and the path of devfns needed to get to it. (Similar to
> the "device scope" structure in the Intel VT-d spec, Section 8.3.1.)
>
> Thus, we add an option to specify devices in the following format:
>
> path:[<domain>:]<bus>:<slot>.<func>/<slot>.<func>[/ ...]
>
> The path can be any segment within the PCI hierarchy of any length and
> determined through the use of 'lspci -t'. When specified this way, it is
> less likely that a renumbered bus will result in a valid device specification
> and the tweak won't be applied to the wrong device.
>
> Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
> Reviewed-by: Stephen Bates <sbates@raithlin.com>
> Acked-by: Christian König <christian.koenig@amd.com>

> -                               specified in one of two formats:
> +                               specified in one of three formats:

...in one of the following formats:

in the first place and don't fix it each time you add/remove one?


-- 
With Best Regards,
Andy Shevchenko
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Re: [PATCH v2 2/3] PCI: Allow specifying devices using a base bus and path of devfns

[Logan Gunthorpe]

On 01/06/18 04:41 AM, Andy Shevchenko wrote:
>> -                               specified in one of two formats:
>> +                               specified in one of three formats:
> 
> ...in one of the following formats:
> 
> in the first place and don't fix it each time you add/remove one?

Sure, I'll make the change in v3.

Thanks,

Logan

Re: [PATCH v2 2/3] PCI: Allow specifying devices using a base bus and path of devfns

[Logan Gunthorpe]

On 01/06/18 04:41 AM, Andy Shevchenko wrote:
>> -                               specified in one of two formats:
>> +                               specified in one of three formats:
> 
> ...in one of the following formats:
> 
> in the first place and don't fix it each time you add/remove one?

Sure, I'll make the change in v3.

Thanks,

Logan
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Re: [PATCH v2 2/3] PCI: Allow specifying devices using a base bus and path of devfns

[Alex Williamson]

On Thu, 31 May 2018 17:50:09 -0600
Logan Gunthorpe <logang@deltatee.com> wrote:

> When specifying PCI devices on the kernel command line using a
> BDF, the bus numbers can change when adding or replacing a device,
> changing motherboard firmware, or applying kernel parameters like
> pci=assign-buses. When this happens, it is usually undesirable to
> apply whatever command line tweak to the wrong device.
> 
> Therefore, it is useful to be able to specify devices with a base
> bus number and the path of devfns needed to get to it. (Similar to
> the "device scope" structure in the Intel VT-d spec, Section 8.3.1.)
> 
> Thus, we add an option to specify devices in the following format:
> 
> path:[<domain>:]<bus>:<slot>.<func>/<slot>.<func>[/ ...]
> 
> The path can be any segment within the PCI hierarchy of any length and
> determined through the use of 'lspci -t'. When specified this way, it is
> less likely that a renumbered bus will result in a valid device specification
> and the tweak won't be applied to the wrong device.
> 
> Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
> Reviewed-by: Stephen Bates <sbates@raithlin.com>
> Acked-by: Christian König <christian.koenig@amd.com>
> ---
>  Documentation/admin-guide/kernel-parameters.txt |  12 ++-
>  drivers/pci/pci.c                               | 101 +++++++++++++++++++++++-
>  2 files changed, 107 insertions(+), 6 deletions(-)
> 
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index e58cc671ff92..bc51b316f485 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -2989,9 +2989,10 @@
>  
>  				Some options herein operate on a specific device
>  				or a set of devices (<pci_dev>). These are
> -				specified in one of two formats:
> +				specified in one of three formats:
>  
>  				[<domain>:]<bus>:<slot>.<func>
> +				path:[<domain>:]<bus>:<slot>.<func>/<slot>.<func>[/ ...]
>  				pci:<vendor>:<device>[:<subvendor>:<subdevice>]
>  
>  				Note: the first format specifies a PCI
> @@ -2999,9 +3000,12 @@
>  				if new hardware is inserted, if motherboard
>  				firmware changes, or due to changes caused
>  				by other kernel parameters. The second format
> -				selects devices using IDs from the
> -				configuration space which may match multiple
> -				devices in the system.
> +				specifies a path from a device through
> +				a path of multiple slot/function addresses
> +				(this is more robust against renumbering
> +				issues). The third format selects devices using
> +				IDs from the configuration space which may match
> +				multiple devices in the system.
>  
>  		earlydump	[X86] dump PCI config space before the kernel
>  			        changes anything
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 85fec5e2640b..39f11bd0ee03 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -184,22 +184,111 @@ EXPORT_SYMBOL_GPL(pci_ioremap_wc_bar);
>  #endif
>  
>  /**
> + * pci_dev_str_match_path - test if a path string matches a device
> + * @dev:    the PCI device to test
> + * @p:      string to match the device against
> + * @endptr: pointer to the string after the match
> + *
> + * Test if a string (typically from a kernel parameter) formated as a
> + * path of slot/function addresses matches a PCI device. The string must
> + * be of the form:
> + *
> + *   [<domain>:]<bus>:<slot>.<func>/<slot>.<func>[/ ...]
> + *
> + * A path for a device can be obtained using 'lspci -t'. Using a path
> + * is more robust against renumbering of devices than using only
> + * a single bus, slot and function address.
> + *
> + * Returns 1 if the string matches the device, 0 if it does not and
> + * a negative error code if it fails to parse the string.
> + */
> +static int pci_dev_str_match_path(struct pci_dev *dev, const char *path,
> +				  const char **endptr)
> +{
> +	int ret;
> +	int seg, bus, slot, func;
> +	char *wpath, *p;
> +	char end;
> +
> +	*endptr = strchrnul(path, ';');
> +
> +	wpath = kmemdup_nul(path, *endptr - path, GFP_KERNEL);
> +	if (!wpath)
> +		return -ENOMEM;
> +
> +	while (1) {
> +		p = strrchr(wpath, '/');
> +		if (!p)
> +			break;
> +		ret = sscanf(p, "/%x.%x%c", &slot, &func, &end);
> +		if (ret != 2) {
> +			ret = -EINVAL;
> +			goto free_and_exit;
> +		}
> +
> +		if (dev->devfn != PCI_DEVFN(slot, func)) {
> +			ret = 0;
> +			goto free_and_exit;
> +		}
> +
> +		/*
> +		 * Note: we don't need to get a reference to the upstream
> +		 * bridge because we hold a reference to the top level
> +		 * device which should hold a reference to the bridge,
> +		 * and so on.
> +		 */
> +		dev = pci_upstream_bridge(dev);
> +		if (!dev) {
> +			ret = 0;
> +			goto free_and_exit;
> +		}
> +
> +		*p = 0;
> +	}
> +
> +	ret = sscanf(wpath, "%x:%x:%x.%x%c", &seg, &bus, &slot,
> +		     &func, &end);
> +	if (ret != 4) {
> +		seg = 0;
> +		ret = sscanf(wpath, "%x:%x.%x%c", &bus, &slot, &func, &end);
> +		if (ret != 3) {
> +			ret = -EINVAL;
> +			goto free_and_exit;
> +		}
> +	}
> +
> +	ret = (seg == pci_domain_nr(dev->bus) &&
> +	       bus == dev->bus->number &&
> +	       dev->devfn == PCI_DEVFN(slot, func));
> +
> +free_and_exit:
> +	kfree(wpath);
> +	return ret;
> +}

Cool, I'm glad this worked.  I note though that there's really not much
difference between:

[domain:]bus:slot.fn

and

[domain:]bus:slot.fn[/slot.fn[/slot.fn[/...]]]

IOW, what's defined here as the "path:" specification doesn't require
that we start at a root bus device, it can really specify a path
starting anywhere, including the target device directly.  So can we
simply extend domain:bus:slot.fn to support paths without a separate
identifier?  Thanks,

Alex

> +
> +/**
>   * pci_dev_str_match - test if a string matches a device
>   * @dev:    the PCI device to test
>   * @p:      string to match the device against
>   * @endptr: pointer to the string after the match
>   *
>   * Test if a string (typically from a kernel parameter) matches a
> - * specified. The string may be of one of two forms formats:
> + * specified. The string may be of one of three formats:
>   *
>   *   [<domain>:]<bus>:<slot>.<func>
> + *   path:[<domain>:]<bus>:<slot>.<func>/<slot>.<func>[/ ...]
>   *   pci:<vendor>:<device>[:<subvendor>:<subdevice>]
>   *
>   * The first format specifies a PCI bus/slot/function address which
>   * may change if new hardware is inserted, if motherboard firmware changes,
>   * or due to changes caused in kernel parameters.
>   *
> - * The second format matches devices using IDs in the configuration
> + * The second format specifies a PCI bus/slot/function root address and
> + * a path of slot/function addresses to the specific device from the root.
> + * The path for a device can be determined through the use of 'lspci -t'.
> + * This format is more robust against renumbering issues than the first format.
> +
> + * The third format matches devices using IDs in the configuration
>   * space which may match multiple devices in the system. A value of 0
>   * for any field will match all devices.
>   *
> @@ -236,7 +325,15 @@ static int pci_dev_str_match(struct pci_dev *dev, const char *p,
>  		    (!subsystem_device ||
>  			    subsystem_device == dev->subsystem_device))
>  			goto found;
> +	} else if (strncmp(p, "path:", 5) == 0) {
> +		/* PCI Root Bus and a path of Slot,Function IDs */
> +		p += 5;
>  
> +		ret = pci_dev_str_match_path(dev, p, &p);
> +		if (ret < 0)
> +			return ret;
> +		else if (ret)
> +			goto found;
>  	} else {
>  		/* PCI Bus,Slot,Function ids are specified */
>  		ret = sscanf(p, "%x:%x:%x.%x%n", &seg, &bus, &slot,

Re: [PATCH v2 2/3] PCI: Allow specifying devices using a base bus and path of devfns

[Alex Williamson]

On Thu, 31 May 2018 17:50:09 -0600
Logan Gunthorpe <logang@deltatee.com> wrote:

> When specifying PCI devices on the kernel command line using a
> BDF, the bus numbers can change when adding or replacing a device,
> changing motherboard firmware, or applying kernel parameters like
> pci=assign-buses. When this happens, it is usually undesirable to
> apply whatever command line tweak to the wrong device.
> 
> Therefore, it is useful to be able to specify devices with a base
> bus number and the path of devfns needed to get to it. (Similar to
> the "device scope" structure in the Intel VT-d spec, Section 8.3.1.)
> 
> Thus, we add an option to specify devices in the following format:
> 
> path:[<domain>:]<bus>:<slot>.<func>/<slot>.<func>[/ ...]
> 
> The path can be any segment within the PCI hierarchy of any length and
> determined through the use of 'lspci -t'. When specified this way, it is
> less likely that a renumbered bus will result in a valid device specification
> and the tweak won't be applied to the wrong device.
> 
> Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
> Reviewed-by: Stephen Bates <sbates@raithlin.com>
> Acked-by: Christian König <christian.koenig@amd.com>
> ---
>  Documentation/admin-guide/kernel-parameters.txt |  12 ++-
>  drivers/pci/pci.c                               | 101 +++++++++++++++++++++++-
>  2 files changed, 107 insertions(+), 6 deletions(-)
> 
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index e58cc671ff92..bc51b316f485 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -2989,9 +2989,10 @@
>  
>  				Some options herein operate on a specific device
>  				or a set of devices (<pci_dev>). These are
> -				specified in one of two formats:
> +				specified in one of three formats:
>  
>  				[<domain>:]<bus>:<slot>.<func>
> +				path:[<domain>:]<bus>:<slot>.<func>/<slot>.<func>[/ ...]
>  				pci:<vendor>:<device>[:<subvendor>:<subdevice>]
>  
>  				Note: the first format specifies a PCI
> @@ -2999,9 +3000,12 @@
>  				if new hardware is inserted, if motherboard
>  				firmware changes, or due to changes caused
>  				by other kernel parameters. The second format
> -				selects devices using IDs from the
> -				configuration space which may match multiple
> -				devices in the system.
> +				specifies a path from a device through
> +				a path of multiple slot/function addresses
> +				(this is more robust against renumbering
> +				issues). The third format selects devices using
> +				IDs from the configuration space which may match
> +				multiple devices in the system.
>  
>  		earlydump	[X86] dump PCI config space before the kernel
>  			        changes anything
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 85fec5e2640b..39f11bd0ee03 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -184,22 +184,111 @@ EXPORT_SYMBOL_GPL(pci_ioremap_wc_bar);
>  #endif
>  
>  /**
> + * pci_dev_str_match_path - test if a path string matches a device
> + * @dev:    the PCI device to test
> + * @p:      string to match the device against
> + * @endptr: pointer to the string after the match
> + *
> + * Test if a string (typically from a kernel parameter) formated as a
> + * path of slot/function addresses matches a PCI device. The string must
> + * be of the form:
> + *
> + *   [<domain>:]<bus>:<slot>.<func>/<slot>.<func>[/ ...]
> + *
> + * A path for a device can be obtained using 'lspci -t'. Using a path
> + * is more robust against renumbering of devices than using only
> + * a single bus, slot and function address.
> + *
> + * Returns 1 if the string matches the device, 0 if it does not and
> + * a negative error code if it fails to parse the string.
> + */
> +static int pci_dev_str_match_path(struct pci_dev *dev, const char *path,
> +				  const char **endptr)
> +{
> +	int ret;
> +	int seg, bus, slot, func;
> +	char *wpath, *p;
> +	char end;
> +
> +	*endptr = strchrnul(path, ';');
> +
> +	wpath = kmemdup_nul(path, *endptr - path, GFP_KERNEL);
> +	if (!wpath)
> +		return -ENOMEM;
> +
> +	while (1) {
> +		p = strrchr(wpath, '/');
> +		if (!p)
> +			break;
> +		ret = sscanf(p, "/%x.%x%c", &slot, &func, &end);
> +		if (ret != 2) {
> +			ret = -EINVAL;
> +			goto free_and_exit;
> +		}
> +
> +		if (dev->devfn != PCI_DEVFN(slot, func)) {
> +			ret = 0;
> +			goto free_and_exit;
> +		}
> +
> +		/*
> +		 * Note: we don't need to get a reference to the upstream
> +		 * bridge because we hold a reference to the top level
> +		 * device which should hold a reference to the bridge,
> +		 * and so on.
> +		 */
> +		dev = pci_upstream_bridge(dev);
> +		if (!dev) {
> +			ret = 0;
> +			goto free_and_exit;
> +		}
> +
> +		*p = 0;
> +	}
> +
> +	ret = sscanf(wpath, "%x:%x:%x.%x%c", &seg, &bus, &slot,
> +		     &func, &end);
> +	if (ret != 4) {
> +		seg = 0;
> +		ret = sscanf(wpath, "%x:%x.%x%c", &bus, &slot, &func, &end);
> +		if (ret != 3) {
> +			ret = -EINVAL;
> +			goto free_and_exit;
> +		}
> +	}
> +
> +	ret = (seg == pci_domain_nr(dev->bus) &&
> +	       bus == dev->bus->number &&
> +	       dev->devfn == PCI_DEVFN(slot, func));
> +
> +free_and_exit:
> +	kfree(wpath);
> +	return ret;
> +}

Cool, I'm glad this worked.  I note though that there's really not much
difference between:

[domain:]bus:slot.fn

and

[domain:]bus:slot.fn[/slot.fn[/slot.fn[/...]]]

IOW, what's defined here as the "path:" specification doesn't require
that we start at a root bus device, it can really specify a path
starting anywhere, including the target device directly.  So can we
simply extend domain:bus:slot.fn to support paths without a separate
identifier?  Thanks,

Alex

> +
> +/**
>   * pci_dev_str_match - test if a string matches a device
>   * @dev:    the PCI device to test
>   * @p:      string to match the device against
>   * @endptr: pointer to the string after the match
>   *
>   * Test if a string (typically from a kernel parameter) matches a
> - * specified. The string may be of one of two forms formats:
> + * specified. The string may be of one of three formats:
>   *
>   *   [<domain>:]<bus>:<slot>.<func>
> + *   path:[<domain>:]<bus>:<slot>.<func>/<slot>.<func>[/ ...]
>   *   pci:<vendor>:<device>[:<subvendor>:<subdevice>]
>   *
>   * The first format specifies a PCI bus/slot/function address which
>   * may change if new hardware is inserted, if motherboard firmware changes,
>   * or due to changes caused in kernel parameters.
>   *
> - * The second format matches devices using IDs in the configuration
> + * The second format specifies a PCI bus/slot/function root address and
> + * a path of slot/function addresses to the specific device from the root.
> + * The path for a device can be determined through the use of 'lspci -t'.
> + * This format is more robust against renumbering issues than the first format.
> +
> + * The third format matches devices using IDs in the configuration
>   * space which may match multiple devices in the system. A value of 0
>   * for any field will match all devices.
>   *
> @@ -236,7 +325,15 @@ static int pci_dev_str_match(struct pci_dev *dev, const char *p,
>  		    (!subsystem_device ||
>  			    subsystem_device == dev->subsystem_device))
>  			goto found;
> +	} else if (strncmp(p, "path:", 5) == 0) {
> +		/* PCI Root Bus and a path of Slot,Function IDs */
> +		p += 5;
>  
> +		ret = pci_dev_str_match_path(dev, p, &p);
> +		if (ret < 0)
> +			return ret;
> +		else if (ret)
> +			goto found;
>  	} else {
>  		/* PCI Bus,Slot,Function ids are specified */
>  		ret = sscanf(p, "%x:%x:%x.%x%n", &seg, &bus, &slot,

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Re: [PATCH v2 2/3] PCI: Allow specifying devices using a base bus and path of devfns

[Logan Gunthorpe]

On 01/06/18 08:30 AM, Alex Williamson wrote:
> Cool, I'm glad this worked.  I note though that there's really not much
> difference between:
> 
> [domain:]bus:slot.fn
> 
> and
> 
> [domain:]bus:slot.fn[/slot.fn[/slot.fn[/...]]]
> 
> IOW, what's defined here as the "path:" specification doesn't require
> that we start at a root bus device, it can really specify a path
> starting anywhere, including the target device directly.  So can we
> simply extend domain:bus:slot.fn to support paths without a separate
> identifier?  Thanks,

Yes, I think you are right. I was just hesitant to change existing
behavior. But if that's the consensus I'll change it for v3.

Thanks,

Logan

Re: [PATCH v2 2/3] PCI: Allow specifying devices using a base bus and path of devfns

[Logan Gunthorpe]

On 01/06/18 08:30 AM, Alex Williamson wrote:
> Cool, I'm glad this worked.  I note though that there's really not much
> difference between:
> 
> [domain:]bus:slot.fn
> 
> and
> 
> [domain:]bus:slot.fn[/slot.fn[/slot.fn[/...]]]
> 
> IOW, what's defined here as the "path:" specification doesn't require
> that we start at a root bus device, it can really specify a path
> starting anywhere, including the target device directly.  So can we
> simply extend domain:bus:slot.fn to support paths without a separate
> identifier?  Thanks,

Yes, I think you are right. I was just hesitant to change existing
behavior. But if that's the consensus I'll change it for v3.

Thanks,

Logan
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[PATCH v2 3/3] PCI: Introduce the disable_acs_redir parameter

[Logan Gunthorpe]

In order to support P2P traffic on a segment of the PCI hierarchy,
we must be able to disable the ACS redirect bits for select
PCI bridges. The bridges must be selected before the devices are
discovered by the kernel and the IOMMU groups created. Therefore,
a kernel command line parameter is created to specify devices
which must have their ACS bits disabled.

The new parameter takes a list of devices separated by a semicolon.
Each device specified will have it's ACS redirect bits disabled.
This is similar to the existing 'resource_alignment' parameter and just
like it we also create a sysfs bus attribute which can be used to
read the parameter. Writing the parameter is not supported
as it would require forcibly hot plugging the affected device as
well as all devices whose IOMMU groups might change.

The ACS Request P2P Request Redirect, P2P Completion Redirect and P2P
Egress Control bits are disabled which is sufficient to always allow
passing P2P traffic uninterrupted. The bits are set after the kernel
(optionally) enables the ACS bits itself. It is also done regardless of
whether the kernel sets the bits or not seeing some BIOS firmware is known
to set the bits on boot.

Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Reviewed-by: Stephen Bates <sbates@raithlin.com>
Acked-by: Christian König <christian.koenig@amd.com>
---
 Documentation/admin-guide/kernel-parameters.txt |   9 +++
 drivers/pci/pci.c                               | 103 +++++++++++++++++++++++-
 2 files changed, 110 insertions(+), 2 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index bc51b316f485..e4a761a2821b 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3179,6 +3179,15 @@
 				Adding the window is slightly risky (it may
 				conflict with unreported devices), so this
 				taints the kernel.
+		disable_acs_redir=<pci_dev>[; ...]
+				Specify one or more PCI devices (in the format
+				specified above) separated by semicolons.
+				Each device specified will have the PCI ACS
+				redirect capabilities forced off which will
+				allow P2P traffic between devices through
+				bridges without forcing it upstream. Note:
+				this removes isolation between devices and
+				will make the IOMMU groups less granular.
 
 	pcie_aspm=	[PCIE] Forcibly enable or disable PCIe Active State Power
 			Management.
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 39f11bd0ee03..7a5f3b97d0ff 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -2993,6 +2993,92 @@ void pci_request_acs(void)
 	pci_acs_enable = 1;
 }
 
+#define DISABLE_ACS_REDIR_PARAM_SIZE COMMAND_LINE_SIZE
+static char disable_acs_redir_param[DISABLE_ACS_REDIR_PARAM_SIZE] = {0};
+static DEFINE_SPINLOCK(disable_acs_redir_lock);
+
+static ssize_t pci_set_disable_acs_redir_param(const char *buf, size_t count)
+{
+	if (count > DISABLE_ACS_REDIR_PARAM_SIZE - 1)
+		count = DISABLE_ACS_REDIR_PARAM_SIZE - 1;
+	spin_lock(&disable_acs_redir_lock);
+	strncpy(disable_acs_redir_param, buf, count);
+	disable_acs_redir_param[count] = '\0';
+	spin_unlock(&disable_acs_redir_lock);
+	return count;
+}
+
+static ssize_t pci_disable_acs_redir_show(struct bus_type *bus, char *buf)
+{
+	size_t count;
+
+	spin_lock(&disable_acs_redir_lock);
+	count = snprintf(buf, PAGE_SIZE, "%s\n", disable_acs_redir_param);
+	spin_unlock(&disable_acs_redir_lock);
+	return count;
+}
+
+static BUS_ATTR(disable_acs_redir, 0444, pci_disable_acs_redir_show, NULL);
+
+static int __init pci_disable_acs_redir_sysfs_init(void)
+{
+	return bus_create_file(&pci_bus_type, &bus_attr_disable_acs_redir);
+}
+late_initcall(pci_disable_acs_redir_sysfs_init);
+
+/**
+ * pci_disable_acs_redir - disable ACS redirect capabilities
+ * @dev: the PCI device
+ *
+ * For only devices specified in the disable_acs_redir parameter.
+ */
+static void pci_disable_acs_redir(struct pci_dev *dev)
+{
+	int ret = 0;
+	const char *p;
+	int pos;
+	u16 ctrl;
+
+	spin_lock(&disable_acs_redir_lock);
+
+	p = disable_acs_redir_param;
+	while (*p) {
+		ret = pci_dev_str_match(dev, p, &p);
+		if (ret < 0) {
+			pr_info_once("PCI: Can't parse disable_acs_redir parameter: %s\n",
+				     disable_acs_redir_param);
+
+			break;
+		} else if (ret == 1) {
+			/* Found a match */
+			break;
+		}
+
+		if (*p != ';' && *p != ',') {
+			/* End of param or invalid format */
+			break;
+		}
+		p++;
+	}
+	spin_unlock(&disable_acs_redir_lock);
+
+	if (ret != 1)
+		return;
+
+	pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ACS);
+	if (!pos)
+		return;
+
+	pci_read_config_word(dev, pos + PCI_ACS_CTRL, &ctrl);
+
+	/* P2P Request & Completion Redirect */
+	ctrl &= ~(PCI_ACS_RR | PCI_ACS_CR | PCI_ACS_EC);
+
+	pci_write_config_word(dev, pos + PCI_ACS_CTRL, ctrl);
+
+	pci_info(dev, "disabled ACS redirect\n");
+}
+
 /**
  * pci_std_enable_acs - enable ACS on devices using standard ACS capabilites
  * @dev: the PCI device
@@ -3032,12 +3118,22 @@ static void pci_std_enable_acs(struct pci_dev *dev)
 void pci_enable_acs(struct pci_dev *dev)
 {
 	if (!pci_acs_enable)
-		return;
+		goto disable_acs_redir;
 
 	if (!pci_dev_specific_enable_acs(dev))
-		return;
+		goto disable_acs_redir;
 
 	pci_std_enable_acs(dev);
+
+disable_acs_redir:
+	/*
+	 * Note: pci_disable_acs_redir() must be called even if
+	 * ACS is not enabled by the kernel because the firmware
+	 * may have unexpectedly set the flags. So if we are told
+	 * to disable it, we should always disable it after setting
+	 * the kernel's default preferences.
+	 */
+	pci_disable_acs_redir(dev);
 }
 
 static bool pci_acs_flags_enabled(struct pci_dev *pdev, u16 acs_flags)
@@ -5990,6 +6086,9 @@ static int __init pci_setup(char *str)
 				pcie_bus_config = PCIE_BUS_PEER2PEER;
 			} else if (!strncmp(str, "pcie_scan_all", 13)) {
 				pci_add_flags(PCI_SCAN_ALL_PCIE_DEVS);
+			} else if (!strncmp(str, "disable_acs_redir=", 18)) {
+				pci_set_disable_acs_redir_param(str + 18,
+					strlen(str + 18));
 			} else {
 				printk(KERN_ERR "PCI: Unknown option `%s'\n",
 						str);
-- 
2.11.0

[PATCH v2 3/3] PCI: Introduce the disable_acs_redir parameter

[Logan Gunthorpe]

In order to support P2P traffic on a segment of the PCI hierarchy,
we must be able to disable the ACS redirect bits for select
PCI bridges. The bridges must be selected before the devices are
discovered by the kernel and the IOMMU groups created. Therefore,
a kernel command line parameter is created to specify devices
which must have their ACS bits disabled.

The new parameter takes a list of devices separated by a semicolon.
Each device specified will have it's ACS redirect bits disabled.
This is similar to the existing 'resource_alignment' parameter and just
like it we also create a sysfs bus attribute which can be used to
read the parameter. Writing the parameter is not supported
as it would require forcibly hot plugging the affected device as
well as all devices whose IOMMU groups might change.

The ACS Request P2P Request Redirect, P2P Completion Redirect and P2P
Egress Control bits are disabled which is sufficient to always allow
passing P2P traffic uninterrupted. The bits are set after the kernel
(optionally) enables the ACS bits itself. It is also done regardless of
whether the kernel sets the bits or not seeing some BIOS firmware is known
to set the bits on boot.

Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Reviewed-by: Stephen Bates <sbates@raithlin.com>
Acked-by: Christian König <christian.koenig@amd.com>
---
 Documentation/admin-guide/kernel-parameters.txt |   9 +++
 drivers/pci/pci.c                               | 103 +++++++++++++++++++++++-
 2 files changed, 110 insertions(+), 2 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index bc51b316f485..e4a761a2821b 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3179,6 +3179,15 @@
 				Adding the window is slightly risky (it may
 				conflict with unreported devices), so this
 				taints the kernel.
+		disable_acs_redir=<pci_dev>[; ...]
+				Specify one or more PCI devices (in the format
+				specified above) separated by semicolons.
+				Each device specified will have the PCI ACS
+				redirect capabilities forced off which will
+				allow P2P traffic between devices through
+				bridges without forcing it upstream. Note:
+				this removes isolation between devices and
+				will make the IOMMU groups less granular.
 
 	pcie_aspm=	[PCIE] Forcibly enable or disable PCIe Active State Power
 			Management.
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 39f11bd0ee03..7a5f3b97d0ff 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -2993,6 +2993,92 @@ void pci_request_acs(void)
 	pci_acs_enable = 1;
 }
 
+#define DISABLE_ACS_REDIR_PARAM_SIZE COMMAND_LINE_SIZE
+static char disable_acs_redir_param[DISABLE_ACS_REDIR_PARAM_SIZE] = {0};
+static DEFINE_SPINLOCK(disable_acs_redir_lock);
+
+static ssize_t pci_set_disable_acs_redir_param(const char *buf, size_t count)
+{
+	if (count > DISABLE_ACS_REDIR_PARAM_SIZE - 1)
+		count = DISABLE_ACS_REDIR_PARAM_SIZE - 1;
+	spin_lock(&disable_acs_redir_lock);
+	strncpy(disable_acs_redir_param, buf, count);
+	disable_acs_redir_param[count] = '\0';
+	spin_unlock(&disable_acs_redir_lock);
+	return count;
+}
+
+static ssize_t pci_disable_acs_redir_show(struct bus_type *bus, char *buf)
+{
+	size_t count;
+
+	spin_lock(&disable_acs_redir_lock);
+	count = snprintf(buf, PAGE_SIZE, "%s\n", disable_acs_redir_param);
+	spin_unlock(&disable_acs_redir_lock);
+	return count;
+}
+
+static BUS_ATTR(disable_acs_redir, 0444, pci_disable_acs_redir_show, NULL);
+
+static int __init pci_disable_acs_redir_sysfs_init(void)
+{
+	return bus_create_file(&pci_bus_type, &bus_attr_disable_acs_redir);
+}
+late_initcall(pci_disable_acs_redir_sysfs_init);
+
+/**
+ * pci_disable_acs_redir - disable ACS redirect capabilities
+ * @dev: the PCI device
+ *
+ * For only devices specified in the disable_acs_redir parameter.
+ */
+static void pci_disable_acs_redir(struct pci_dev *dev)
+{
+	int ret = 0;
+	const char *p;
+	int pos;
+	u16 ctrl;
+
+	spin_lock(&disable_acs_redir_lock);
+
+	p = disable_acs_redir_param;
+	while (*p) {
+		ret = pci_dev_str_match(dev, p, &p);
+		if (ret < 0) {
+			pr_info_once("PCI: Can't parse disable_acs_redir parameter: %s\n",
+				     disable_acs_redir_param);
+
+			break;
+		} else if (ret == 1) {
+			/* Found a match */
+			break;
+		}
+
+		if (*p != ';' && *p != ',') {
+			/* End of param or invalid format */
+			break;
+		}
+		p++;
+	}
+	spin_unlock(&disable_acs_redir_lock);
+
+	if (ret != 1)
+		return;
+
+	pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ACS);
+	if (!pos)
+		return;
+
+	pci_read_config_word(dev, pos + PCI_ACS_CTRL, &ctrl);
+
+	/* P2P Request & Completion Redirect */
+	ctrl &= ~(PCI_ACS_RR | PCI_ACS_CR | PCI_ACS_EC);
+
+	pci_write_config_word(dev, pos + PCI_ACS_CTRL, ctrl);
+
+	pci_info(dev, "disabled ACS redirect\n");
+}
+
 /**
  * pci_std_enable_acs - enable ACS on devices using standard ACS capabilites
  * @dev: the PCI device
@@ -3032,12 +3118,22 @@ static void pci_std_enable_acs(struct pci_dev *dev)
 void pci_enable_acs(struct pci_dev *dev)
 {
 	if (!pci_acs_enable)
-		return;
+		goto disable_acs_redir;
 
 	if (!pci_dev_specific_enable_acs(dev))
-		return;
+		goto disable_acs_redir;
 
 	pci_std_enable_acs(dev);
+
+disable_acs_redir:
+	/*
+	 * Note: pci_disable_acs_redir() must be called even if
+	 * ACS is not enabled by the kernel because the firmware
+	 * may have unexpectedly set the flags. So if we are told
+	 * to disable it, we should always disable it after setting
+	 * the kernel's default preferences.
+	 */
+	pci_disable_acs_redir(dev);
 }
 
 static bool pci_acs_flags_enabled(struct pci_dev *pdev, u16 acs_flags)
@@ -5990,6 +6086,9 @@ static int __init pci_setup(char *str)
 				pcie_bus_config = PCIE_BUS_PEER2PEER;
 			} else if (!strncmp(str, "pcie_scan_all", 13)) {
 				pci_add_flags(PCI_SCAN_ALL_PCIE_DEVS);
+			} else if (!strncmp(str, "disable_acs_redir=", 18)) {
+				pci_set_disable_acs_redir_param(str + 18,
+					strlen(str + 18));
 			} else {
 				printk(KERN_ERR "PCI: Unknown option `%s'\n",
 						str);
-- 
2.11.0

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