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msi: set 'En' bit of MSI Mapping Capability

PATCH In review peerchen 4 participants 12 messages Dec 18, 2007 – Jan 7, 2008

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#0 lore raw

PATCH 1/1 msi: set 'En' bit of MSI Mapping Capability

According to the HyperTransport spec, 'En' indicate if the MSI Mapping is active. Set the 'En' bit when setup pci and add the quirk for some nvidia devices.

The patch base on kernel 2.6.24-rc5

Signed-off-by Andy Currid <[email protected]>
Signed-off-by Peer Chen <[email protected]>

---

drivers/pci/probe.c +3 -0
diff -uprN -X linux-2.6.24-rc5-vanilla/Documentation/dontdiff linux-2.6.24-rc5-vanilla/drivers/pci/probe.c linux-2.6.24-rc5/drivers/pci/probe.c
@@ -721,6 +721,9 @@ static int pci_setup_device(struct pci_d
 
 	/* "Unknown power state" */
 	dev->current_state = PCI_UNKNOWN;
+	
+	/* Enable HT MSI mapping */
+	ht_enable_msi_mapping(dev);
 
 	/* Early fixups, before probing the BARs */
 	pci_fixup_device(pci_fixup_early, dev);
drivers/pci/quirks.c +39 -0
diff -uprN -X linux-2.6.24-rc5-vanilla/Documentation/dontdiff linux-2.6.24-rc5-vanilla/drivers/pci/quirks.c linux-2.6.24-rc5/drivers/pci/quirks.c
@@ -1705,6 +1705,45 @@ static void __devinit quirk_nvidia_ck804
 DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_NVIDIA, PCI_DEVICE_ID_NVIDIA_CK804_PCIE,
 			quirk_nvidia_ck804_msi_ht_cap);
 
+static void __devinit quirk_msi_ht_cap_disable(struct pci_dev *dev) {
+	struct pci_dev *host_bridge;
+	int pos, ttl = 48;
+
+	/* HT MSI mapping should be disabled on devices that are below
+	 * a non-Hypertransport host bridge. Locate the host bridge...
+ 	 */
+
+	if ((host_bridge = pci_get_bus_and_slot(0, PCI_DEVFN(0,0))) == NULL) {
+		printk(KERN_WARNING
+			 "PCI: quirk_msi_ht_cap_disable didn't locate host bridge\n");
+		return;
+	}
+
+	if ((pos = pci_find_ht_capability(host_bridge, HT_CAPTYPE_SLAVE)) != 0) {
+		/* Host bridge is to HT */
+		return;
+	}
+
+	/* Host bridge is not to HT, disable HT MSI mapping on this device */
+
+	pos = pci_find_ht_capability(dev, HT_CAPTYPE_MSI_MAPPING);
+	while (pos && ttl--) {
+		u8 flags;
+
+		if (pci_read_config_byte(dev, pos + HT_MSI_FLAGS, &flags) == 0) {
+			printk(KERN_INFO "PCI: Quirk disabling HT MSI mapping on %s\n",
+			       pci_name(dev));
+
+			pci_write_config_byte(dev, pos + HT_MSI_FLAGS,
+					      flags & ~HT_MSI_FLAGS_ENABLE);
+		}
+		pos = pci_find_next_ht_capability(dev, pos,
+						  HT_CAPTYPE_MSI_MAPPING);
+	}
+}
+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_NVIDIA, PCI_ANY_ID,
+							quirk_msi_ht_cap_disable);
+
 static void __devinit quirk_msi_intx_disable_bug(struct pci_dev *dev)
 {
 	dev->dev_flags |= PCI_DEV_FLAGS_MSI_INTX_DISABLE_BUG;
include/asm-generic/pci.h +4 -0
diff -uprN -X linux-2.6.24-rc5-vanilla/Documentation/dontdiff linux-2.6.24-rc5-vanilla/include/asm-generic/pci.h linux-2.6.24-rc5/include/asm-generic/pci.h
@@ -45,6 +45,10 @@ pcibios_select_root(struct pci_dev *pdev
 
 #define pcibios_scan_all_fns(a, b)	0
 
+#ifndef HAVE_ARCH_HT_ENABLE_MSI_MAPPING
+#define ht_enable_msi_mapping(a)	0
+#endif /* HAVE_ARCH_HT_ENABLE_MSI_MAPPING */
+
 #ifndef HAVE_ARCH_PCI_GET_LEGACY_IDE_IRQ
 static inline int pci_get_legacy_ide_irq(struct pci_dev *dev, int channel)
 {
include/asm-x86/pci.h +21 -1
diff -uprN -X linux-2.6.24-rc5-vanilla/Documentation/dontdiff linux-2.6.24-rc5-vanilla/include/asm-x86/pci.h linux-2.6.24-rc5/include/asm-x86/pci.h
@@ -75,6 +75,27 @@ static inline void pci_dma_burst_advice(
 }
 #endif
 
+#ifdef CONFIG_PCI
+#define HAVE_ARCH_HT_ENABLE_MSI_MAPPING
+static inline void ht_enable_msi_mapping(struct pci_dev *dev)
+{
+	int pos, ttl = 48;
+
+	pos = pci_find_ht_capability(dev, HT_CAPTYPE_MSI_MAPPING);
+	while (pos && ttl--) {
+		u8 flags;
+
+		if (pci_read_config_byte(dev, pos + HT_MSI_FLAGS, &flags) == 0) {
+			printk(KERN_INFO "PCI: Enabling HT MSI Mapping on %s\n",
+						dev->dev.bus_id);
+
+			pci_write_config_byte(dev, pos + HT_MSI_FLAGS,
+					      flags | HT_MSI_FLAGS_ENABLE);
+		}
+		pos = pci_find_next_ht_capability(dev, pos, HT_CAPTYPE_MSI_MAPPING);
+	}
+}
+#endif
 
 #endif  /* __KERNEL__ */
-
#1 lore raw
Quoted 5 lines · peerchen

According to the HyperTransport spec, 'En' indicate if the MSI Mapping is active.
Set the 'En' bit when setup pci and add the quirk for some nvidia devices.

The patch base on kernel 2.6.24-rc5

Ok. This is starting to look good.

Quoted 58 lines
Signed-off-by Andy Currid <[email protected]>
Signed-off-by Peer Chen <[email protected]>

---
diff -uprN -X linux-2.6.24-rc5-vanilla/Documentation/dontdiff linux-2.6.24-rc5-vanilla/drivers/pci/probe.c linux-2.6.24-rc5/drivers/pci/probe.c
--- linux-2.6.24-rc5-vanilla/drivers/pci/probe.c 2007-12-18 14:35:46.000000000 -0500
+++ linux-2.6.24-rc5/drivers/pci/probe.c 2007-12-18 16:28:29.000000000 -0500

drivers/pci/probe.c +3 -0
@@ -721,6 +721,9 @@ static int pci_setup_device(struct pci_d
 
 	/* "Unknown power state" */
 	dev->current_state = PCI_UNKNOWN;
+	
+	/* Enable HT MSI mapping */
+	ht_enable_msi_mapping(dev);
 
 	/* Early fixups, before probing the BARs */
 	pci_fixup_device(pci_fixup_early, dev);

diff -uprN -X linux-2.6.24-rc5-vanilla/Documentation/dontdiff linux-2.6.24-rc5-vanilla/drivers/pci/quirks.c linux-2.6.24-rc5/drivers/pci/quirks.c
--- linux-2.6.24-rc5-vanilla/drivers/pci/quirks.c 2007-12-18 14:35:46.000000000 -0500
+++ linux-2.6.24-rc5/drivers/pci/quirks.c 2007-12-18 16:28:41.000000000 -0500

drivers/pci/quirks.c +28 -0
@@ -1705,6 +1705,45 @@ static void __devinit quirk_nvidia_ck804
 DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_NVIDIA, PCI_DEVICE_ID_NVIDIA_CK804_PCIE,
 			quirk_nvidia_ck804_msi_ht_cap);
 
+static void __devinit quirk_msi_ht_cap_disable(struct pci_dev *dev) {
+	struct pci_dev *host_bridge;
+	int pos, ttl = 48;
+
+	/* HT MSI mapping should be disabled on devices that are below
+	 * a non-Hypertransport host bridge. Locate the host bridge...
+ 	 */
+
+	if ((host_bridge = pci_get_bus_and_slot(0, PCI_DEVFN(0,0))) == NULL) {
+		printk(KERN_WARNING
+ "PCI: quirk_msi_ht_cap_disable didn't locate host bridge\n");
+		return;
+	}
+
+ if ((pos = pci_find_ht_capability(host_bridge, HT_CAPTYPE_SLAVE)) != 0) {
+		/* Host bridge is to HT */
+		return;
+	}
+
+	/* Host bridge is not to HT, disable HT MSI mapping on this device */
+
+	pos = pci_find_ht_capability(dev, HT_CAPTYPE_MSI_MAPPING);
+	while (pos && ttl--) {
+		u8 flags;
+
+ if (pci_read_config_byte(dev, pos + HT_MSI_FLAGS, &flags) == 0) {
+ printk(KERN_INFO "PCI: Quirk disabling HT MSI mapping on %s\n",
+			       pci_name(dev));

drivers/pci/quirks.c static void __devinit quirk_nvidia_ck804 · line 1745

Quoted 10 lines
drivers/pci/quirks.c +10 -0
+
+			pci_write_config_byte(dev, pos + HT_MSI_FLAGS,
+					      flags & ~HT_MSI_FLAGS_ENABLE);
+		}
+		pos = pci_find_next_ht_capability(dev, pos,
+						  HT_CAPTYPE_MSI_MAPPING);
+	}
+}
+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_NVIDIA, PCI_ANY_ID,
+ quirk_msi_ht_cap_disable);

Could you explain the need for this quirk?

My expectation would be that if we turned an MSI interrupt into a hypertransport interrupt then if we hit a non-hyptransport bridge upstream it would just turn the hypertransport interrupts into whatever makes sense for the upstream bridge. I can see it being excess work and adding some latency but I don't see it being a correctness problem.

Or are my expectations off and the NVIDIA chipsets do not handle hypertransport interrupts the way I would expect. Dropping them instead of converting when going to a non-hypertransport host bridge.

Quoted 37 lines
drivers/pci/quirks.c +0 -0
 static void __devinit quirk_msi_intx_disable_bug(struct pci_dev *dev)
 {
 	dev->dev_flags |= PCI_DEV_FLAGS_MSI_INTX_DISABLE_BUG;

diff -uprN -X linux-2.6.24-rc5-vanilla/Documentation/dontdiff linux-2.6.24-rc5-vanilla/include/asm-generic/pci.h linux-2.6.24-rc5/include/asm-generic/pci.h
--- linux-2.6.24-rc5-vanilla/include/asm-generic/pci.h 2007-12-18 14:35:52.000000000 -0500
+++ linux-2.6.24-rc5/include/asm-generic/pci.h 2007-12-18 16:29:12.000000000 -0500

include/asm-generic/pci.h +4 -0
@@ -45,6 +45,10 @@ pcibios_select_root(struct pci_dev *pdev
 
 #define pcibios_scan_all_fns(a, b)	0
 
+#ifndef HAVE_ARCH_HT_ENABLE_MSI_MAPPING
+#define ht_enable_msi_mapping(a)	0
+#endif /* HAVE_ARCH_HT_ENABLE_MSI_MAPPING */
+
 #ifndef HAVE_ARCH_PCI_GET_LEGACY_IDE_IRQ
 static inline int pci_get_legacy_ide_irq(struct pci_dev *dev, int channel)
 {

diff -uprN -X linux-2.6.24-rc5-vanilla/Documentation/dontdiff linux-2.6.24-rc5-vanilla/include/asm-x86/pci.h linux-2.6.24-rc5/include/asm-x86/pci.h
--- linux-2.6.24-rc5-vanilla/include/asm-x86/pci.h 2007-12-18 14:35:51.000000000 -0500
+++ linux-2.6.24-rc5/include/asm-x86/pci.h 2007-12-18 16:28:58.000000000 -0500

include/asm-x86/pci.h +6 -0
@@ -75,6 +75,27 @@ static inline void pci_dma_burst_advice(
 }
 #endif
 
+#ifdef CONFIG_PCI
+#define HAVE_ARCH_HT_ENABLE_MSI_MAPPING
+static inline void ht_enable_msi_mapping(struct pci_dev *dev)
+{
+	int pos, ttl = 48;
+

include/asm-x86/pci.h static inline void pci_dma_burst_advice( · line 93

Quoted 10 lines
include/asm-x86/pci.h +10 -0
+	pos = pci_find_ht_capability(dev, HT_CAPTYPE_MSI_MAPPING);
+	while (pos && ttl--) {
+		u8 flags;
+
+ if (pci_read_config_byte(dev, pos + HT_MSI_FLAGS, &flags) == 0) {
+ printk(KERN_INFO "PCI: Enabling HT MSI Mapping on %s\n",
+						dev->dev.bus_id);
+
+			pci_write_config_byte(dev, pos + HT_MSI_FLAGS,
+					      flags | HT_MSI_FLAGS_ENABLE);

Here I see two things that we should do better.
1) If the BIOS has already properly enabled the capability we don't need to do anything or print any message. i.e.

   if (!(flags & HT_MSI_FLAGS_ENABLE)) {
	printk(...)
        pci_write_config_byte()

}

2) The hypertransport specification allows for an optional register that specifies the address of the msi mapping window. If that register is present we should program it to the architectural defined address on x86 before enabling the device.

Quoted 8 lines
include/asm-x86/pci.h +5 -1
+		}
+ pos = pci_find_next_ht_capability(dev, pos, HT_CAPTYPE_MSI_MAPPING);
+	}
+}
+#endif
 
 #endif  /* __KERNEL__ */
-
#2 lore raw

The quirk is for our Intel platform, we don't want HT MSI mapping enabled in any of our devices.

BRs
Peer Chen

-----Original Message-----
From: Eric W. Biederman [mailto:[email protected]]
Sent: Wednesday, December 19, 2007 5:59 AM
To: peerchen
Cc: linux-kernel; akpm; Andy Currid; Peer Chen
Subject: Re: [PATCH] msi: set 'En' bit of MSI Mapping Capability

Quoted 1 line · peerchen

According to the HyperTransport spec, 'En' indicate if the MSI Mapping

is

Quoted 2 lines

active.
Set the 'En' bit when setup pci and add the quirk for some nvidia

devices.

Quoted 2 lines

The patch base on kernel 2.6.24-rc5

Ok. This is starting to look good.

Quoted 8 lines
Signed-off-by Andy Currid <[email protected]>
Signed-off-by Peer Chen <[email protected]>

---
diff -uprN -X linux-2.6.24-rc5-vanilla/Documentation/dontdiff linux-2.6.24-rc5-vanilla/drivers/pci/probe.c linux-2.6.24-rc5/drivers/pci/probe.c
--- linux-2.6.24-rc5-vanilla/drivers/pci/probe.c 2007-12-18

14:35:46.000000000

Quoted 2 lines

-0500
+++ linux-2.6.24-rc5/drivers/pci/probe.c 2007-12-18 16:28:29.000000000

-0500

Quoted 10 lines
drivers/pci/probe.c +3 -0
@@ -721,6 +721,9 @@ static int pci_setup_device(struct pci_d
 
 	/* "Unknown power state" */
 	dev->current_state = PCI_UNKNOWN;
+	
+	/* Enable HT MSI mapping */
+	ht_enable_msi_mapping(dev);
 
 	/* Early fixups, before probing the BARs */
 	pci_fixup_device(pci_fixup_early, dev);
Quoted 4 lines

diff -uprN -X linux-2.6.24-rc5-vanilla/Documentation/dontdiff linux-2.6.24-rc5-vanilla/drivers/pci/quirks.c linux-2.6.24-rc5/drivers/pci/quirks.c
--- linux-2.6.24-rc5-vanilla/drivers/pci/quirks.c 2007-12-18

14:35:46.000000000

Quoted 2 lines

-0500
+++ linux-2.6.24-rc5/drivers/pci/quirks.c 2007-12-18

16:28:41.000000000 -0500

Review static void __devinit quirk_nvidia_ck804 · line 1705

Quoted 2 lines
(quoted diff) +0 -0
@@ -1705,6 +1705,45 @@ static void __devinit quirk_nvidia_ck804
 DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_NVIDIA,

PCI_DEVICE_ID_NVIDIA_CK804_PCIE,

drivers/pci/quirks.c static void __devinit quirk_nvidia_ck804

Quoted 11 lines
drivers/pci/quirks.c +9 -0
 			quirk_nvidia_ck804_msi_ht_cap);
 
+static void __devinit quirk_msi_ht_cap_disable(struct pci_dev *dev) {
+	struct pci_dev *host_bridge;
+	int pos, ttl = 48;
+
+	/* HT MSI mapping should be disabled on devices that are below
+	 * a non-Hypertransport host bridge. Locate the host bridge...
+ 	 */
+
+	if ((host_bridge = pci_get_bus_and_slot(0, PCI_DEVFN(0,0))) ==

NULL) {

drivers/pci/quirks.c static void __devinit quirk_nvidia_ck804

Quoted 6 lines
drivers/pci/quirks.c +6 -0
+		printk(KERN_WARNING
+ "PCI: quirk_msi_ht_cap_disable didn't locate host bridge\n");
+		return;
+	}
+
+ if ((pos = pci_find_ht_capability(host_bridge, HT_CAPTYPE_SLAVE)) !=

0) {

drivers/pci/quirks.c static void __devinit quirk_nvidia_ck804

Quoted 5 lines
drivers/pci/quirks.c +5 -0
+		/* Host bridge is to HT */
+		return;
+	}
+
+	/* Host bridge is not to HT, disable HT MSI mapping on this

device */

drivers/pci/quirks.c static void __devinit quirk_nvidia_ck804

Quoted 11 lines
drivers/pci/quirks.c +11 -0
+
+	pos = pci_find_ht_capability(dev, HT_CAPTYPE_MSI_MAPPING);
+	while (pos && ttl--) {
+		u8 flags;
+
+ if (pci_read_config_byte(dev, pos + HT_MSI_FLAGS, &flags) == 0) {
+ printk(KERN_INFO "PCI: Quirk disabling HT MSI mapping on %s\n",
+			       pci_name(dev));
+
+			pci_write_config_byte(dev, pos + HT_MSI_FLAGS,
+					      flags &

~HT_MSI_FLAGS_ENABLE);

drivers/pci/quirks.c static void __devinit quirk_nvidia_ck804 · line 1746

Quoted 3 lines
drivers/pci/quirks.c +3 -0
+		}
+		pos = pci_find_next_ht_capability(dev, pos,
+

HT_CAPTYPE_MSI_MAPPING);

drivers/pci/quirks.c static void __devinit quirk_nvidia_ck804 · line 1745

Quoted 4 lines
drivers/pci/quirks.c +4 -0
+	}
+}
+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_NVIDIA, PCI_ANY_ID,
+ quirk_msi_ht_cap_disable);

Could you explain the need for this quirk?

My expectation would be that if we turned an MSI interrupt into a hypertransport interrupt then if we hit a non-hyptransport bridge upstream it would just turn the hypertransport interrupts into whatever makes sense for the upstream bridge. I can see it being excess work and adding some latency but I don't see it being a correctness problem.

Or are my expectations off and the NVIDIA chipsets do not handle hypertransport interrupts the way I would expect. Dropping them instead of converting when going to a non-hypertransport host bridge.

Quoted 9 lines
drivers/pci/quirks.c +0 -0
 static void __devinit quirk_msi_intx_disable_bug(struct pci_dev *dev)
 {
 	dev->dev_flags |= PCI_DEV_FLAGS_MSI_INTX_DISABLE_BUG;

diff -uprN -X linux-2.6.24-rc5-vanilla/Documentation/dontdiff linux-2.6.24-rc5-vanilla/include/asm-generic/pci.h linux-2.6.24-rc5/include/asm-generic/pci.h
--- linux-2.6.24-rc5-vanilla/include/asm-generic/pci.h 2007-12-18 14:35:52.000000000 -0500
+++ linux-2.6.24-rc5/include/asm-generic/pci.h 2007-12-18

16:29:12.000000000

include/asm-generic/pci.h pcibios_select_root(struct pci_dev *pdev · line 53

Quoted 11 lines

-0500

include/asm-generic/pci.h +4 -0
@@ -45,6 +45,10 @@ pcibios_select_root(struct pci_dev *pdev
 
 #define pcibios_scan_all_fns(a, b)	0
 
+#ifndef HAVE_ARCH_HT_ENABLE_MSI_MAPPING
+#define ht_enable_msi_mapping(a)	0
+#endif /* HAVE_ARCH_HT_ENABLE_MSI_MAPPING */
+
 #ifndef HAVE_ARCH_PCI_GET_LEGACY_IDE_IRQ
 static inline int pci_get_legacy_ide_irq(struct pci_dev *dev, int

channel)

Quoted 5 lines
(quoted diff) +0 -0
 {

diff -uprN -X linux-2.6.24-rc5-vanilla/Documentation/dontdiff linux-2.6.24-rc5-vanilla/include/asm-x86/pci.h linux-2.6.24-rc5/include/asm-x86/pci.h
--- linux-2.6.24-rc5-vanilla/include/asm-x86/pci.h 2007-12-18

14:35:51.000000000

Quoted 2 lines

-0500
+++ linux-2.6.24-rc5/include/asm-x86/pci.h 2007-12-18

16:28:58.000000000 -0500

Quoted 10 lines
include/asm-x86/pci.h +6 -0
@@ -75,6 +75,27 @@ static inline void pci_dma_burst_advice(
 }
 #endif
 
+#ifdef CONFIG_PCI
+#define HAVE_ARCH_HT_ENABLE_MSI_MAPPING
+static inline void ht_enable_msi_mapping(struct pci_dev *dev)
+{
+	int pos, ttl = 48;
+

include/asm-x86/pci.h static inline void pci_dma_burst_advice( · line 93

Quoted 10 lines
include/asm-x86/pci.h +10 -0
+	pos = pci_find_ht_capability(dev, HT_CAPTYPE_MSI_MAPPING);
+	while (pos && ttl--) {
+		u8 flags;
+
+ if (pci_read_config_byte(dev, pos + HT_MSI_FLAGS, &flags) == 0) {
+ printk(KERN_INFO "PCI: Enabling HT MSI Mapping on %s\n",
+						dev->dev.bus_id);
+
+			pci_write_config_byte(dev, pos + HT_MSI_FLAGS,
+					      flags |

HT_MSI_FLAGS_ENABLE);

Here I see two things that we should do better.
1) If the BIOS has already properly enabled the capability we don't need to do anything or print any message. i.e.

   if (!(flags & HT_MSI_FLAGS_ENABLE)) {
	printk(...)
        pci_write_config_byte()

}

2) The hypertransport specification allows for an optional register that specifies the address of the msi mapping window. If that register is present we should program it to the architectural defined address on x86 before enabling the device.

include/asm-x86/pci.h static inline void pci_dma_burst_advice( · line 80

Quoted 8 lines
include/asm-x86/pci.h +5 -1
+		}
+ pos = pci_find_next_ht_capability(dev, pos, HT_CAPTYPE_MSI_MAPPING);
+	}
+}
+#endif
 
 #endif  /* __KERNEL__ */
-

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#3 lore raw
Quoted 2 lines · Peer Chen

The quirk is for our Intel platform, we don't want HT MSI mapping enabled in any of our devices.

Why is this a problem? I seem to recall a real hypertransport bus downstream of the Intel cpu.

If there is a real hypertransport bus in the middle then what happens if someone puts a tunnel that uses hypertransport between the two chips?

I feel very dense right now. I don't understand why enabling the mapping on an Intel based system is a problem. I am afraid there is some important gap in my understanding in which case we may need to rethink enabling the hypertransport capability by default.

If disabling the hypertransport bus is simply an optimization, or it is to deal with an issue that appears exclusive to Nvidia chips I have no problem with your quirk.

Eric

#4 lore raw

I feel it's dangerous to set the En bit on Intel platform, If the HT MSI En is set, the MSI should be expected to transform to HT INT message format. It may cause interrupt lost or hardware internal state machine failed depend on the hardware design.

BRs
Peer Chen

-----Original Message-----
From: Eric W. Biederman [mailto:[email protected]]
Sent: Friday, December 21, 2007 6:48 AM
To: Peer Chen
Cc: peerchen; linux-kernel; akpm; Andy Currid
Subject: Re: [PATCH] msi: set 'En' bit of MSI Mapping Capability

Quoted 2 lines · Peer Chen

The quirk is for our Intel platform, we don't want HT MSI mapping enabled in any of our devices.

Why is this a problem? I seem to recall a real hypertransport bus downstream of the Intel cpu.

If there is a real hypertransport bus in the middle then what happens if someone puts a tunnel that uses hypertransport between the two chips?

I feel very dense right now. I don't understand why enabling the mapping on an Intel based system is a problem. I am afraid there is some important gap in my understanding in which case we may need to rethink enabling the hypertransport capability by default.

If disabling the hypertransport bus is simply an optimization, or it is to deal with an issue that appears exclusive to Nvidia chips I have no problem with your quirk.

Eric
-----------------------------------------------------------------------------------
This email message is for the sole use of the intended recipient(s) and may contain confidential information. Any unauthorized review, use, disclosure or distribution is prohibited. If you are not the intended recipient, please contact the sender by reply email and destroy all copies of the original message.
-----------------------------------------------------------------------------------

#5 lore raw
Quoted 4 lines · Peer Chen

I feel it's dangerous to set the En bit on Intel platform, If the HT MSI En is set, the MSI should be expected to transform to HT INT message format. It may cause interrupt lost or hardware internal state machine failed depend on the hardware design.

Reasonable. As long as what the quirk is to avoid errata and chipset specific issues I don't have a problem with it.

I figure the quirk should be a separate patch though.

My concern is that the general rule that always enabling HT MSI mapping capabilities is reasonable. Even if there are some specific exceptions where we don't want to do that.

I want code that requires the smallest list of chipset exceptions that we can make.

Eric

#6 lore raw

I think it's more reasonable to only apply this rule onto AMD platform.

BRs
Peer Chen

-----Original Message-----
From: Eric W. Biederman [mailto:[email protected]]
Sent: Monday, December 24, 2007 7:49 PM
To: Peer Chen
Cc: peerchen; linux-kernel; akpm; Andy Currid
Subject: Re: [PATCH] msi: set 'En' bit of MSI Mapping Capability

Quoted 1 line · Peer Chen

I feel it's dangerous to set the En bit on Intel platform, If the HT

MSI

Quoted 3 lines

En is set, the MSI should be expected to transform to HT INT message format. It may cause interrupt lost or hardware internal state machine failed depend on the hardware design.

Reasonable. As long as what the quirk is to avoid errata and chipset specific issues I don't have a problem with it.

I figure the quirk should be a separate patch though.

My concern is that the general rule that always enabling HT MSI mapping capabilities is reasonable. Even if there are some specific exceptions where we don't want to do that.

I want code that requires the smallest list of chipset exceptions that we can make.

Eric
-----------------------------------------------------------------------------------
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#7 lore raw
In reply to Eric W. Biederman

Eric,
Any decision for this patch, if not, currently we prefer to add all our code to quirks.c.

BRs
Peer Chen

-----Original Message-----
From: Peer Chen
Sent: Wednesday, January 02, 2008 5:58 PM
To: 'Eric W. Biederman'
Cc: peerchen; linux-kernel; akpm; Andy Currid
Subject: RE: [PATCH] msi: set 'En' bit of MSI Mapping Capability

I think it's more reasonable to only apply this rule onto AMD platform.

BRs
Peer Chen

-----Original Message-----
From: Eric W. Biederman [mailto:[email protected]]
Sent: Monday, December 24, 2007 7:49 PM
To: Peer Chen
Cc: peerchen; linux-kernel; akpm; Andy Currid
Subject: Re: [PATCH] msi: set 'En' bit of MSI Mapping Capability

Quoted 1 line · Peer Chen

I feel it's dangerous to set the En bit on Intel platform, If the HT

MSI

Quoted 3 lines

En is set, the MSI should be expected to transform to HT INT message format. It may cause interrupt lost or hardware internal state machine failed depend on the hardware design.

Reasonable. As long as what the quirk is to avoid errata and chipset specific issues I don't have a problem with it.

I figure the quirk should be a separate patch though.

My concern is that the general rule that always enabling HT MSI mapping capabilities is reasonable. Even if there are some specific exceptions where we don't want to do that.

I want code that requires the smallest list of chipset exceptions that we can make.

Eric
-----------------------------------------------------------------------------------
This email message is for the sole use of the intended recipient(s) and may contain confidential information. Any unauthorized review, use, disclosure or distribution is prohibited. If you are not the intended recipient, please contact the sender by reply email and destroy all copies of the original message.
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#8 lore raw
Quoted 3 lines · Peer Chen

Eric,
Any decision for this patch, if not, currently we prefer to add all our code to quirks.c.

Sorry. I think adding the code to quirks.c is fine.

For bisection and code inspection purposes I would prefer the code to come as a patchset of two patches. With the generic change first.

I wanted to understand where you were coming from to make certain I had not looked over something generic. The closest to generic I can make of your concern is that we are doing useless work if we know there is an upstream msi to irq mapper that we can just tunnel to over hypertransport. At the generic level we can't know that there is an upstream mapping capability as nothing reports it, so we even if it is a good idea we can't do anything.

So a quirk looks fine to do what you are doing.

Just please next round handle the address part of the msi mapping capability if it is present, in the x86 part of the generic code. Just in case someone implements that.

Eric

#9 lore raw
In reply to peerchen
Quoted 26 lines · On Tue, 18 Dec 2007 23:00:52 +0800 "peerchen" <[email protected]> wrote:

According to the HyperTransport spec, 'En' indicate if the MSI Mapping is active. Set the 'En' bit when setup pci and add the quirk for some nvidia devices.

The patch base on kernel 2.6.24-rc5

Signed-off-by Andy Currid <[email protected]>
Signed-off-by Peer Chen <[email protected]>

---
diff -uprN -X linux-2.6.24-rc5-vanilla/Documentation/dontdiff linux-2.6.24-rc5-vanilla/drivers/pci/probe.c linux-2.6.24-rc5/drivers/pci/probe.c

drivers/pci/probe.c +3 -0
@@ -721,6 +721,9 @@ static int pci_setup_device(struct pci_d
 
 	/* "Unknown power state" */
 	dev->current_state = PCI_UNKNOWN;
+	
+	/* Enable HT MSI mapping */
+	ht_enable_msi_mapping(dev);
 
 	/* Early fixups, before probing the BARs */
 	pci_fixup_device(pci_fixup_early, dev);

diff -uprN -X linux-2.6.24-rc5-vanilla/Documentation/dontdiff linux-2.6.24-rc5-vanilla/drivers/pci/quirks.c linux-2.6.24-rc5/drivers/pci/quirks.c

drivers/pci/quirks.c static void __devinit quirk_nvidia_ck804 · line 1708

Quoted 4 lines
drivers/pci/quirks.c +1 -0
@@ -1705,6 +1705,45 @@ static void __devinit quirk_nvidia_ck804
 DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_NVIDIA, PCI_DEVICE_ID_NVIDIA_CK804_PCIE,
 			quirk_nvidia_ck804_msi_ht_cap);
 
+static void __devinit quirk_msi_ht_cap_disable(struct pci_dev *dev) {

Please feed all diffs through scripts/checkpatch.pl and review the results.

Quoted 27 lines
drivers/pci/quirks.c +27 -0
+	struct pci_dev *host_bridge;
+	int pos, ttl = 48;
+
+	/* HT MSI mapping should be disabled on devices that are below
+	 * a non-Hypertransport host bridge. Locate the host bridge...
+ 	 */
+
+	if ((host_bridge = pci_get_bus_and_slot(0, PCI_DEVFN(0,0))) == NULL) {
+		printk(KERN_WARNING
+			 "PCI: quirk_msi_ht_cap_disable didn't locate host bridge\n");
+		return;
+	}
+
+	if ((pos = pci_find_ht_capability(host_bridge, HT_CAPTYPE_SLAVE)) != 0) {
+		/* Host bridge is to HT */
+		return;
+	}
+
+	/* Host bridge is not to HT, disable HT MSI mapping on this device */
+
+	pos = pci_find_ht_capability(dev, HT_CAPTYPE_MSI_MAPPING);
+	while (pos && ttl--) {
+		u8 flags;
+
+		if (pci_read_config_byte(dev, pos + HT_MSI_FLAGS, &flags) == 0) {
+			printk(KERN_INFO "PCI: Quirk disabling HT MSI mapping on %s\n",
+			       pci_name(dev));

drivers/pci/quirks.c static void __devinit quirk_nvidia_ck804 · line 1745

Quoted 10 lines
drivers/pci/quirks.c +10 -0
+
+			pci_write_config_byte(dev, pos + HT_MSI_FLAGS,
+					      flags & ~HT_MSI_FLAGS_ENABLE);
+		}
+		pos = pci_find_next_ht_capability(dev, pos,
+						  HT_CAPTYPE_MSI_MAPPING);
+	}
+}
+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_NVIDIA, PCI_ANY_ID,
+							quirk_msi_ht_cap_disable);

This limit of 48 iterations (ttl) is mysterious. Perhaps it is described in the spec? Either way, I believe it should be documented in code comments because there is no way on earth that the code reader can tell why it is there.

include/asm-generic/pci.h pcibios_select_root(struct pci_dev *pdev · line 50

Quoted 13 lines
drivers/pci/quirks.c +0 -0
 static void __devinit quirk_msi_intx_disable_bug(struct pci_dev *dev)
 {
 	dev->dev_flags |= PCI_DEV_FLAGS_MSI_INTX_DISABLE_BUG;

diff -uprN -X linux-2.6.24-rc5-vanilla/Documentation/dontdiff linux-2.6.24-rc5-vanilla/include/asm-generic/pci.h linux-2.6.24-rc5/include/asm-generic/pci.h

include/asm-generic/pci.h +3 -0
@@ -45,6 +45,10 @@ pcibios_select_root(struct pci_dev *pdev
 
 #define pcibios_scan_all_fns(a, b)	0
 
+#ifndef HAVE_ARCH_HT_ENABLE_MSI_MAPPING
+#define ht_enable_msi_mapping(a)	0
+#endif /* HAVE_ARCH_HT_ENABLE_MSI_MAPPING */

Please try to avoid the HAVE_ARCH_foo trick. It's fairly ugly. You can do the Linus trick of:

#ifndef ht_enable_msi_mapping
#define ht_enable_msi_mapping(x) do { } while (0)
#endif

and then, in include/asm-x86/pci.h, do

static inline void ht_enable_msi_mapping(struct pci_dev *dev)

{
	...
}

#define ht_enable_msi_mapping(d) ht_enable_msi_mapping(d)

which has the merit of reducing the number of global symbols, but it's still pretty unpleasant.

It would be better to just add a stub implementation of ht_enable_msi_mapping() for all the other architectures - avoid fancy cpp tricks.

Also, your proposed non-x86 implementation of ht_enable_msi_mapping() is (effectively) an integer-returning thing whereas your x86 implementation is a void-returning thing. Consequently non-x86 architectures will get a statement-with-no-effect warning when this patch is applied.

Quoted 21 lines
include/asm-generic/pci.h +0 -0
 #ifndef HAVE_ARCH_PCI_GET_LEGACY_IDE_IRQ
 static inline int pci_get_legacy_ide_irq(struct pci_dev *dev, int channel)
 {

diff -uprN -X linux-2.6.24-rc5-vanilla/Documentation/dontdiff linux-2.6.24-rc5-vanilla/include/asm-x86/pci.h linux-2.6.24-rc5/include/asm-x86/pci.h

include/asm-x86/pci.h +11 -0
@@ -75,6 +75,27 @@ static inline void pci_dma_burst_advice(
 }
 #endif
 
+#ifdef CONFIG_PCI
+#define HAVE_ARCH_HT_ENABLE_MSI_MAPPING
+static inline void ht_enable_msi_mapping(struct pci_dev *dev)
+{
+	int pos, ttl = 48;
+
+	pos = pci_find_ht_capability(dev, HT_CAPTYPE_MSI_MAPPING);
+	while (pos && ttl--) {
+		u8 flags;
+
+		if (pci_read_config_byte(dev, pos + HT_MSI_FLAGS, &flags) == 0) {

include/asm-x86/pci.h static inline void pci_dma_burst_advice( · line 98

Quoted 10 lines
include/asm-x86/pci.h +10 -0
+			printk(KERN_INFO "PCI: Enabling HT MSI Mapping on %s\n",
+						dev->dev.bus_id);
+
+			pci_write_config_byte(dev, pos + HT_MSI_FLAGS,
+					      flags | HT_MSI_FLAGS_ENABLE);
+		}
+		pos = pci_find_next_ht_capability(dev, pos, HT_CAPTYPE_MSI_MAPPING);
+	}
+}
+#endif

And even though this has only a single callsite, there really is no point in inlining it. It's not a fastpath and putting a large and complex function like this in a header file risks increasing that header file's include dependencies.

iow, let's put it in arch/x86/pci/ somewhere?

#10 lore raw
Quoted 3 lines · On Wed, 19 Dec 2007 16:41:25 -0800 Andrew Morton <[email protected]>…

It would be better to just add a stub implementation of ht_enable_msi_mapping() for all the other architectures - avoid fancy cpp tricks.

And by this I really do mean going into each include/asm-*/pci.h and adding

struct pci_dev; (if needed)
...

static inline void ht_enable_msi_mapping(struct pci_dev *dev) {
}

no macros, no ifdef tricks, no include tricks. Just straight, clean, fully typechecked C.

#11 lore raw
Quoted 14 lines · Andrew Morton
Quoted 3 lines · On Wed, 19 Dec 2007 16:41:25 -0800 Andrew Morton <[email protected]>…

It would be better to just add a stub implementation of ht_enable_msi_mapping() for all the other architectures - avoid fancy cpp tricks.

And by this I really do mean going into each include/asm-*/pci.h and adding

struct pci_dev; (if needed)
...

Quoted 7 lines

static inline void ht_enable_msi_mapping(struct pci_dev *dev) {
}

no macros, no ifdef tricks, no include tricks. Just straight, clean, fully typechecked C.

Andrew thanks for the code style review. I goofed about recommending the ARCH_HAVE_XXXX thing.

I'm going to concentrate on the content for the moment. I think we are very close to a general solution to a very common problem with MSI interrupts.

Eric