kernel/linux.git/arch/powerpc/include/asm/rtas.h, branch v6.6.141

powerpc/rtas: use correct function name for resetting TCE tables

2024-03-06T14:48:43+00:00

[ Upstream commit fad87dbd48156ab940538f052f1820f4b6ed2819 ] The PAPR spec spells the function name as "ibm,reset-pe-dma-windows" but in practice firmware uses the singular form: "ibm,reset-pe-dma-window" in the device tree. Since we have the wrong spelling in the RTAS function table, reverse lookups (token -> name) fail and warn: unexpected failed lookup for token 86 WARNING: CPU: 1 PID: 545 at arch/powerpc/kernel/rtas.c:659 __do_enter_rtas_trace+0x2a4/0x2b4 CPU: 1 PID: 545 Comm: systemd-udevd Not tainted 6.8.0-rc4 #30 Hardware name: IBM,9105-22A POWER10 (raw) 0x800200 0xf000006 of:IBM,FW1060.00 (NL1060_028) hv:phyp pSeries NIP [c0000000000417f0] __do_enter_rtas_trace+0x2a4/0x2b4 LR [c0000000000417ec] __do_enter_rtas_trace+0x2a0/0x2b4 Call Trace: __do_enter_rtas_trace+0x2a0/0x2b4 (unreliable) rtas_call+0x1f8/0x3e0 enable_ddw.constprop.0+0x4d0/0xc84 dma_iommu_dma_supported+0xe8/0x24c dma_set_mask+0x5c/0xd8 mlx5_pci_init.constprop.0+0xf0/0x46c [mlx5_core] probe_one+0xfc/0x32c [mlx5_core] local_pci_probe+0x68/0x12c pci_call_probe+0x68/0x1ec pci_device_probe+0xbc/0x1a8 really_probe+0x104/0x570 __driver_probe_device+0xb8/0x224 driver_probe_device+0x54/0x130 __driver_attach+0x158/0x2b0 bus_for_each_dev+0xa8/0x120 driver_attach+0x34/0x48 bus_add_driver+0x174/0x304 driver_register+0x8c/0x1c4 __pci_register_driver+0x68/0x7c mlx5_init+0xb8/0x118 [mlx5_core] do_one_initcall+0x60/0x388 do_init_module+0x7c/0x2a4 init_module_from_file+0xb4/0x108 idempotent_init_module+0x184/0x34c sys_finit_module+0x90/0x114 And oopses are possible when lockdep is enabled or the RTAS tracepoints are active, since those paths dereference the result of the lookup. Use the correct spelling to match firmware's behavior, adjusting the related constants to match. Signed-off-by: Nathan Lynch Fixes: 8252b88294d2 ("powerpc/rtas: improve function information lookups") Reported-by: Gaurav Batra Signed-off-by: Michael Ellerman Link: https://msgid.link/20240222-rtas-fix-ibm-reset-pe-dma-window-v1-1-7aaf235ac63c@linux.ibm.com Signed-off-by: Sasha Levin

powerpc/rtas: export rtas_error_rc() for reuse.

2023-08-18T13:28:57+00:00

Also, #define descriptive names for common rtas return codes and use it instead of numeric values. Signed-off-by: Mahesh Salgaonkar Signed-off-by: Michael Ellerman Link: https://msgid.link/169235811556.193557.1023625262204809514.stgit@jupiter

powerpc/rtas: introduce rtas_function_token() API

2023-02-13T11:35:03+00:00

Users of rtas_token() supply a string argument that can't be validated at build time. A typo or misspelling has to be caught by inspection or by observing wrong behavior at runtime. Since the core RTAS code now has consolidated the names of all possible RTAS functions and mapped them to their tokens, token lookup can be implemented using symbolic constants to index a static array. So introduce rtas_function_token(), a replacement API which does that, along with a rtas_service_present()-equivalent helper, rtas_function_implemented(). Callers supply an opaque predefined function handle which is used internally to index the function table. Typos or other inappropriate arguments yield build errors, and the function handle is a type that can't be easily confused with RTAS tokens or other integer types. Signed-off-by: Nathan Lynch Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20230125-b4-powerpc-rtas-queue-v3-19-26929c8cce78@linux.ibm.com

powerpc/rtas: improve function information lookups

2023-02-13T11:35:02+00:00

The core RTAS support code and its clients perform two types of lookup for RTAS firmware function information. First, mapping a known function name to a token. The typical use case invokes rtas_token() to retrieve the token value to pass to rtas_call(). rtas_token() relies on of_get_property(), which performs a linear search of the /rtas node's property list under a lock with IRQs disabled. Second, and less common: given a token value, looking up some information about the function. The primary example is the sys_rtas filter path, which linearly scans a small table to match the token to a rtas_filter struct. Another use case to come is RTAS entry/exit tracepoints, which will require efficient lookup of function names from token values. Currently there is no general API for this. We need something much like the existing rtas_filters table, but more general and organized to facilitate efficient lookups. Introduce: * A new rtas_function type, aggregating function name, token, and filter. Other function characteristics could be added in the future. * An array of rtas_function, where each element corresponds to a known RTAS function. All information in the table is static save the token values, which are derived from the device tree at boot. The array is sorted by function name to allow binary search. * A named constant for each known RTAS function, used to index the function array. These also will be used in a client-facing API to be added later. * An xarray that maps valid tokens to rtas_function objects. Fold the existing rtas_filter table into the new rtas_function array, with the appropriate adjustments to block_rtas_call(). Remove now-redundant fields from struct rtas_filter. Preserve the function of the CONFIG_CPU_BIG_ENDIAN guard in the current filter table by introducing a per-function flag that is set for the function entries related to pseries LPAR migration. These have never had working users via sys_rtas on ppc64le; see commit de0f7349a0dd ("powerpc/rtas: prevent suspend-related sys_rtas use on LE"). Convert rtas_token() to use a lockless binary search on the function table. Fall back to the old behavior for lookups against names that are not known to be RTAS functions, but issue a warning. rtas_token() is for function names; it is not a general facility for accessing arbitrary properties of the /rtas node. All known misuses of rtas_token() have been converted to more appropriate of_ APIs in preceding changes. Signed-off-by: Nathan Lynch Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20230125-b4-powerpc-rtas-queue-v3-8-26929c8cce78@linux.ibm.com

powerpc/rtas: document rtas_call()

2022-12-07T11:20:33+00:00

rtas_call() has a complex calling convention, non-standard return values, and many users. Add kernel-doc for it and remove the less structured commentary from rtas.h. Signed-off-by: Nathan Lynch Reviewed-by: Andrew Donnellan Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20221118150751.469393-2-nathanl@linux.ibm.com

Revert "powerpc/rtas: Implement reentrant rtas call"

2022-09-14T12:43:13+00:00

At the time this was submitted by Leonardo, I confirmed -- or thought I had confirmed -- with PowerVM partition firmware development that the following RTAS functions: - ibm,get-xive - ibm,int-off - ibm,int-on - ibm,set-xive were safe to call on multiple CPUs simultaneously, not only with respect to themselves as indicated by PAPR, but with arbitrary other RTAS calls: https://lore.kernel.org/linuxppc-dev/875zcy2v8o.fsf@linux.ibm.com/ Recent discussion with firmware development makes it clear that this is not true, and that the code in commit b664db8e3f97 ("powerpc/rtas: Implement reentrant rtas call") is unsafe, likely explaining several strange bugs we've seen in internal testing involving DLPAR and LPM. These scenarios use ibm,configure-connector, whose internal state can be corrupted by the concurrent use of the "reentrant" functions, leading to symptoms like endless busy statuses from RTAS. Fixes: b664db8e3f97 ("powerpc/rtas: Implement reentrant rtas call") Cc: stable@vger.kernel.org # v5.8+ Signed-off-by: Nathan Lynch Reviewed-by: Laurent Dufour Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20220907220111.223267-1-nathanl@linux.ibm.com

powerpc/pseries: make pseries_devicetree_update() static

2022-02-12T11:47:44+00:00

pseries_devicetree_update() has only one call site, in the same file in which it is defined. Make it static. Signed-off-by: Nathan Lynch Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20220207221247.354454-1-nathanl@linux.ibm.com

powerpc/rtas: rtas_busy_delay() improvements

2021-11-25T00:25:33+00:00

Generally RTAS cannot block, and in PAPR it is required to return control to the OS within a few tens of microseconds. In order to support operations which may take longer to complete, many RTAS primitives can return intermediate -2 ("busy") or 990x ("extended delay") values, which indicate that the OS should reattempt the same call with the same arguments at some point in the future. Current versions of PAPR are less than clear about this, but the intended meanings of these values in more detail are: RTAS_BUSY (-2): RTAS has suspended a potentially long-running operation in order to meet its latency obligation and give the OS the opportunity to perform other work. RTAS can resume making progress as soon as the OS reattempts the call. RTAS_EXTENDED_DELAY_{MIN...MAX} (9900-9905): RTAS must wait for an external event to occur or for internal contention to resolve before it can complete the requested operation. The value encodes a non-binding hint as to roughly how long the OS should wait before calling again, but the OS is allowed to reattempt the call sooner or even immediately. Linux of course must take its own CPU scheduling obligations into account when handling these statuses; e.g. a task which receives an RTAS_BUSY status should check whether to reschedule before it attempts the RTAS call again to avoid starving other tasks. rtas_busy_delay() is a helper function that "consumes" a busy or extended delay status. Common usage: int rc; do { rc = rtas_call(rtas_token("some-function"), ...); } while (rtas_busy_delay(rc)); /* convert rc to Linux error value, etc */ If rc is a busy or extended delay status, the caller can rely on rtas_busy_delay() to perform an appropriate sleep or reschedule and return nonzero. Other statuses are handled normally by the caller. The current implementation of rtas_busy_delay() both oversleeps and overuses the CPU: * It performs msleep() for all 990x and even when no delay is suggested (-2), but this is understood to actually sleep for two jiffies minimum in practice (20ms with HZ=100). 9900 (1ms) and 9901 (10ms) appear to be the most common extended delay statuses, and the oversleeping measurably lengthens DLPAR operations, which perform many RTAS calls. * It does not sleep on 990x unless need_resched() is true, causing code like the loop above to needlessly retry, wasting CPU time. Alter the logic to align better with the intended meanings: * When passed RTAS_BUSY, perform cond_resched() and return without sleeping. The caller should reattempt immediately * Always sleep when passed an extended delay status, using usleep_range() for precise shorter sleeps. Limit the sleep time to one second even though there are higher architected values. Change rtas_busy_delay()'s return type to bool to better reflect its usage, and add kernel-doc. rtas_busy_delay_time() is unchanged, even though it "incorrectly" returns 1 for RTAS_BUSY. There are users of that API with open-coded delay loops in sensitive contexts that will have to be taken on an individual basis. Brief results for addition and removal of 5GB memory on a small P9 PowerVM partition follow. Load was generated with stress-ng --cpu N. For add, elapsed time is greatly reduced without significant change in the number of RTAS calls or time spent on CPU. For remove, elapsed time is modestly reduced, with significant reductions in RTAS calls and time spent on CPU. With no competing workload (- before, + after): Performance counter stats for 'bash -c echo "memory add count 20" > /sys/kernel/dlpar' (10 runs): - 1,935 probe:rtas_call # 0.003 M/sec ( +- 0.22% ) - 609.99 msec task-clock # 0.183 CPUs utilized ( +- 0.19% ) + 1,956 probe:rtas_call # 0.003 M/sec ( +- 0.17% ) + 618.56 msec task-clock # 0.278 CPUs utilized ( +- 0.11% ) - 3.3322 +- 0.0670 seconds time elapsed ( +- 2.01% ) + 2.2222 +- 0.0416 seconds time elapsed ( +- 1.87% ) Performance counter stats for 'bash -c echo "memory remove count 20" > /sys/kernel/dlpar' (10 runs): - 6,224 probe:rtas_call # 0.008 M/sec ( +- 2.57% ) - 750.36 msec task-clock # 0.190 CPUs utilized ( +- 2.01% ) + 843 probe:rtas_call # 0.003 M/sec ( +- 0.12% ) + 250.66 msec task-clock # 0.068 CPUs utilized ( +- 0.17% ) - 3.9394 +- 0.0890 seconds time elapsed ( +- 2.26% ) + 3.678 +- 0.113 seconds time elapsed ( +- 3.07% ) With all CPUs 100% busy (- before, + after): Performance counter stats for 'bash -c echo "memory add count 20" > /sys/kernel/dlpar' (10 runs): - 2,979 probe:rtas_call # 0.003 M/sec ( +- 0.12% ) - 1,096.62 msec task-clock # 0.105 CPUs utilized ( +- 0.10% ) + 2,981 probe:rtas_call # 0.003 M/sec ( +- 0.22% ) + 1,095.26 msec task-clock # 0.154 CPUs utilized ( +- 0.21% ) - 10.476 +- 0.104 seconds time elapsed ( +- 1.00% ) + 7.1124 +- 0.0865 seconds time elapsed ( +- 1.22% ) Performance counter stats for 'bash -c echo "memory remove count 20" > /sys/kernel/dlpar' (10 runs): - 2,702 probe:rtas_call # 0.004 M/sec ( +- 4.00% ) - 722.71 msec task-clock # 0.067 CPUs utilized ( +- 2.41% ) + 1,246 probe:rtas_call # 0.003 M/sec ( +- 0.25% ) + 487.73 msec task-clock # 0.049 CPUs utilized ( +- 0.20% ) - 10.829 +- 0.163 seconds time elapsed ( +- 1.51% ) + 9.9887 +- 0.0866 seconds time elapsed ( +- 0.87% ) Signed-off-by: Nathan Lynch Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20211117060259.957178-2-nathanl@linux.ibm.com

powerpc/rtas: rename RTAS_RMOBUF_MAX to RTAS_USER_REGION_SIZE

2021-04-14T13:04:16+00:00

RTAS_RMOBUF_MAX doesn't actually describe a "maximum" value in any sense. It represents the size of an area of memory set aside for user space to use as work areas for certain RTAS calls. Rename it to RTAS_USER_REGION_SIZE. Signed-off-by: Nathan Lynch Reviewed-by: Andrew Donnellan Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20210408140630.205502-6-nathanl@linux.ibm.com

powerpc: remove unneeded semicolons

2021-02-08T13:10:50+00:00

Remove superfluous semicolons after function definitions. Signed-off-by: Chengyang Fan Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20210125095338.1719405-1-cy.fan@huawei.com