firewire: Enable remote DMA above 4 GB

This makes all of a machine's memory accessible to remote debugging via FireWire, using the physical response unit (i.e. RDMA) of OHCI-1394 link layer controllers. This requires actual support by the controller. The only ones currently known to support it are Agere/LSI FW643. Most if not all other OHCI-1394 controllers do not implement the optional Physical Upper Bound register. With them, RDMA will continue to be limited to the lowermost 4 GB. firewire-ohci's startup message in the kernel log is augmented to tell whether the controller does expose more than 4 GB to RDMA. While OHCI-1394 allows for a maximum Physical Upper Bound of 0xffff'0000'0000 (near 256 TB), this implementation sets it to 0x8000'0000'0000 (128 TB) in order to avoid interference with applications that require interrupt-served asynchronous request reception at respectively low addresses. Note, this change does not switch remote DMA on. It only increases the range of remote access to all memory (instead of just 4 GB) whenever remote DMA was switched on by other means. The latter is achieved by setting firewire-ohci's remote_dma parameter, or if the physical DMA filter is opened through firewire-sbp2. Derived from patch "firewire: Enable physical DMA above 4GB" by Peter Hurley <peter@hurleysoftware.com> from March 27, 2013. Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>

firewire: Enable remote DMA above 4 GB
This makes all of a machine's memory accessible to remote debugging via FireWire, using the physical response unit (i.e. RDMA) of OHCI-1394 link layer controllers. This requires actual support by the controller. The only ones currently known to support it are Agere/LSI FW643. Most if not all other OHCI-1394 controllers do not implement the optional Physical Upper Bound register. With them, RDMA will continue to be limited to the lowermost 4 GB. firewire-ohci's startup message in the kernel log is augmented to tell whether the controller does expose more than 4 GB to RDMA. While OHCI-1394 allows for a maximum Physical Upper Bound of 0xffff'0000'0000 (near 256 TB), this implementation sets it to 0x8000'0000'0000 (128 TB) in order to avoid interference with applications that require interrupt-served asynchronous request reception at respectively low addresses. Note, this change does not switch remote DMA on. It only increases the range of remote access to all memory (instead of just 4 GB) whenever remote DMA was switched on by other means. The latter is achieved by setting firewire-ohci's remote_dma parameter, or if the physical DMA filter is opened through firewire-sbp2. Derived from patch "firewire: Enable physical DMA above 4GB" by Peter Hurley <peter@hurleysoftware.com> from March 27, 2013. Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
Stefan Richter · Eric Lee · Eric Lee · Eric Lee · Eric Lee · Eric Lee
1 parent 8bc588e0e5
Showing 4 changed files with 20 additions and 10 deletions Side-by-side Diff
Documentation/debugging-via-ohci1394.txt
drivers/firewire/core-transaction.c
drivers/firewire/core.h
drivers/firewire/ohci.c
@@ -22,10 +22,12 @@
 Retrieving a full system memory dump is also possible over the FireWire,
 using data transfer rates in the order of 10MB/s or more.
  
-Memory access is currently limited to the low 4G of physical address
-space which can be a problem on IA64 machines where memory is located
-mostly above that limit, but it is rarely a problem on more common
-hardware such as hardware based on x86, x86-64 and PowerPC.
+With most FireWire controllers, memory access is limited to the low 4 GB
+of physical address space.  This can be a problem on IA64 machines where
+memory is located mostly above that limit, but it is rarely a problem on
+more common hardware such as x86, x86-64 and PowerPC.  However, at least
+Agere/LSI FW643e and FW643e2 controllers are known to support access to
+physical addresses above 4 GB.
  
 Together with a early initialization of the OHCI-1394 controller for debugging,
 this facility proved most useful for examining long debugs logs in the printk
@@ -98,6 +100,9 @@
    systems, it most likely is. Only specialized shops have cards which are not
    compliant, they are based on TI PCILynx chips and require drivers for Win-
    dows operating systems.
+
+   The mentioned kernel log message contains ">4 GB phys DMA" in case of
+   OHCI-1394 controllers which support accesses above this limit.
  
 2) Establish a working FireWire cable connection:
  
@@ -523,11 +523,11 @@
 static LIST_HEAD(address_handler_list);
  
 const struct fw_address_region fw_high_memory_region =
-	{ .start = 0x000100000000ULL, .end = 0xffffe0000000ULL,  };
+	{ .start = FW_MAX_PHYSICAL_RANGE, .end = 0xffffe0000000ULL, };
 EXPORT_SYMBOL(fw_high_memory_region);
  
 static const struct fw_address_region low_memory_region =
-	{ .start = 0x000000000000ULL, .end = 0x000100000000ULL,  };
+	{ .start = 0x000000000000ULL, .end = FW_MAX_PHYSICAL_RANGE, };
  
 #if 0
 const struct fw_address_region fw_private_region =
@@ -1217,7 +1217,7 @@
 }
  
 static struct fw_address_handler low_memory = {
-	.length			= 0x000100000000ULL,
+	.length			= FW_MAX_PHYSICAL_RANGE,
 	.address_callback	= handle_low_memory,
 };
  
@@ -237,6 +237,9 @@
  
 #define LOCAL_BUS 0xffc0
  
+/* arbitrarily chosen maximum range for physical DMA: 128 TB */
+#define FW_MAX_PHYSICAL_RANGE		(128ULL << 40)
+
 void fw_core_handle_request(struct fw_card *card, struct fw_packet *request);
 void fw_core_handle_response(struct fw_card *card, struct fw_packet *packet);
 int fw_get_response_length(struct fw_request *request);
@@ -2367,7 +2367,7 @@
 	reg_write(ohci, OHCI1394_FairnessControl, 0);
 	card->priority_budget_implemented = ohci->pri_req_max != 0;
  
-	reg_write(ohci, OHCI1394_PhyUpperBound, 0x00010000);
+	reg_write(ohci, OHCI1394_PhyUpperBound, FW_MAX_PHYSICAL_RANGE >> 16);
 	reg_write(ohci, OHCI1394_IntEventClear, ~0);
 	reg_write(ohci, OHCI1394_IntMaskClear, ~0);
  
  
@@ -3723,9 +3723,11 @@
 	version = reg_read(ohci, OHCI1394_Version) & 0x00ff00ff;
 	ohci_notice(ohci,
 		    "added OHCI v%x.%x device as card %d, "
-		    "%d IR + %d IT contexts, quirks 0x%x\n",
+		    "%d IR + %d IT contexts, quirks 0x%x%s\n",
 		    version >> 16, version & 0xff, ohci->card.index,
-		    ohci->n_ir, ohci->n_it, ohci->quirks);
+		    ohci->n_ir, ohci->n_it, ohci->quirks,
+		    reg_read(ohci, OHCI1394_PhyUpperBound) ?
+			", >4 GB phys DMA" : "");
  
 	return 0;
...	...	@@ -22,10 +22,12 @@
22	22	Retrieving a full system memory dump is also possible over the FireWire,
23	23	using data transfer rates in the order of 10MB/s or more.
24	24
25		-Memory access is currently limited to the low 4G of physical address
26		-space which can be a problem on IA64 machines where memory is located
27		-mostly above that limit, but it is rarely a problem on more common
28		-hardware such as hardware based on x86, x86-64 and PowerPC.
	25	+With most FireWire controllers, memory access is limited to the low 4 GB
	26	+of physical address space. This can be a problem on IA64 machines where
	27	+memory is located mostly above that limit, but it is rarely a problem on
	28	+more common hardware such as x86, x86-64 and PowerPC. However, at least
	29	+Agere/LSI FW643e and FW643e2 controllers are known to support access to
	30	+physical addresses above 4 GB.
29	31
30	32	Together with a early initialization of the OHCI-1394 controller for debugging,
31	33	this facility proved most useful for examining long debugs logs in the printk
...	...	@@ -98,6 +100,9 @@
98	100	systems, it most likely is. Only specialized shops have cards which are not
99	101	compliant, they are based on TI PCILynx chips and require drivers for Win-
100	102	dows operating systems.
	103	+
	104	+ The mentioned kernel log message contains ">4 GB phys DMA" in case of
	105	+ OHCI-1394 controllers which support accesses above this limit.
101	106
102	107	2) Establish a working FireWire cable connection:
103	108
...	...	@@ -523,11 +523,11 @@
523	523	static LIST_HEAD(address_handler_list);
524	524
525	525	const struct fw_address_region fw_high_memory_region =
526		- { .start = 0x000100000000ULL, .end = 0xffffe0000000ULL, };
	526	+ { .start = FW_MAX_PHYSICAL_RANGE, .end = 0xffffe0000000ULL, };
527	527	EXPORT_SYMBOL(fw_high_memory_region);
528	528
529	529	static const struct fw_address_region low_memory_region =
530		- { .start = 0x000000000000ULL, .end = 0x000100000000ULL, };
	530	+ { .start = 0x000000000000ULL, .end = FW_MAX_PHYSICAL_RANGE, };
531	531
532	532	#if 0
533	533	const struct fw_address_region fw_private_region =
...	...	@@ -1217,7 +1217,7 @@
1217	1217	}
1218	1218
1219	1219	static struct fw_address_handler low_memory = {
1220		- .length = 0x000100000000ULL,
	1220	+ .length = FW_MAX_PHYSICAL_RANGE,
1221	1221	.address_callback = handle_low_memory,
1222	1222	};
1223	1223
...	...	@@ -237,6 +237,9 @@
237	237
238	238	#define LOCAL_BUS 0xffc0
239	239
	240	+/* arbitrarily chosen maximum range for physical DMA: 128 TB */
	241	+#define FW_MAX_PHYSICAL_RANGE (128ULL << 40)
	242	+
240	243	void fw_core_handle_request(struct fw_card card, struct fw_packet request);
241	244	void fw_core_handle_response(struct fw_card card, struct fw_packet packet);
242	245	int fw_get_response_length(struct fw_request *request);
...	...	@@ -2367,7 +2367,7 @@
2367	2367	reg_write(ohci, OHCI1394_FairnessControl, 0);
2368	2368	card->priority_budget_implemented = ohci->pri_req_max != 0;
2369	2369
2370		- reg_write(ohci, OHCI1394_PhyUpperBound, 0x00010000);
	2370	+ reg_write(ohci, OHCI1394_PhyUpperBound, FW_MAX_PHYSICAL_RANGE >> 16);
2371	2371	reg_write(ohci, OHCI1394_IntEventClear, ~0);
2372	2372	reg_write(ohci, OHCI1394_IntMaskClear, ~0);
2373	2373
2374	2374
...	...	@@ -3723,9 +3723,11 @@
3723	3723	version = reg_read(ohci, OHCI1394_Version) & 0x00ff00ff;
3724	3724	ohci_notice(ohci,
3725	3725	"added OHCI v%x.%x device as card %d, "
3726		- "%d IR + %d IT contexts, quirks 0x%x\n",
	3726	+ "%d IR + %d IT contexts, quirks 0x%x%s\n",
3727	3727	version >> 16, version & 0xff, ohci->card.index,
3728		- ohci->n_ir, ohci->n_it, ohci->quirks);
	3728	+ ohci->n_ir, ohci->n_it, ohci->quirks,
	3729	+ reg_read(ohci, OHCI1394_PhyUpperBound) ?
	3730	+ ", >4 GB phys DMA" : "");
3729	3731
3730	3732	return 0;
3731	3733