linux/drivers/resctrl/mpam_internal.h

753 lines
23 KiB

2025-11-19 12:22:48 +00:00
arm_mpam: Add helpers for managing the locking around the mon_sel registers The MSC MON_SEL register needs to be accessed from hardirq for the overflow interrupt, and when taking an IPI to access these registers on platforms where MSC are not accessible from every CPU. This makes an irqsave spinlock the obvious lock to protect these registers. On systems with SCMI or PCC mailboxes it must be able to sleep, meaning a mutex must be used. The SCMI or PCC platforms can't support an overflow interrupt, and can't access the registers from hardirq context. Clearly these two can't exist for one MSC at the same time. Add helpers for the MON_SEL locking. For now, use a irqsave spinlock and only support 'real' MMIO platforms. In the future this lock will be split in two allowing SCMI/PCC platforms to take a mutex. Because there are contexts where the SCMI/PCC platforms can't make an access, mpam_mon_sel_lock() needs to be able to fail. Do this now, so that all the error handling on these paths is present. This allows the relevant paths to fail if they are needed on a platform where this isn't possible, instead of having to make explicit checks of the interface type. Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com> Reviewed-by: Gavin Shan <gshan@redhat.com> Reviewed-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com> Reviewed-by: Fenghua Yu <fenghuay@nvidia.com> Tested-by: Fenghua Yu <fenghuay@nvidia.com> Tested-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com> Tested-by: Peter Newman <peternewman@google.com> Tested-by: Carl Worth <carl@os.amperecomputing.com> Tested-by: Gavin Shan <gshan@redhat.com> Tested-by: Zeng Heng <zengheng4@huawei.com> Tested-by: Hanjun Guo <guohanjun@huawei.com> Signed-off-by: James Morse <james.morse@arm.com> Signed-off-by: Ben Horgan <ben.horgan@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
2025-11-19 12:22:45 +00:00
arm64: mpam: Context switch the MPAM registers MPAM allows traffic in the SoC to be labeled by the OS, these labels are used to apply policy in caches and bandwidth regulators, and to monitor traffic in the SoC. The label is made up of a PARTID and PMG value. The x86 equivalent calls these CLOSID and RMID, but they don't map precisely. MPAM has two CPU system registers that is used to hold the PARTID and PMG values that traffic generated at each exception level will use. These can be set per-task by the resctrl file system. (resctrl is the defacto interface for controlling this stuff). Add a helper to switch this. struct task_struct's separate CLOSID and RMID fields are insufficient to implement resctrl using MPAM, as resctrl can change the PARTID (CLOSID) and PMG (sort of like the RMID) separately. On x86, the rmid is an independent number, so a race that writes a mismatched closid and rmid into hardware is benign. On arm64, the pmg bits extend the partid. (i.e. partid-5 has a pmg-0 that is not the same as partid-6's pmg-0). In this case, mismatching the values will 'dirty' a pmg value that resctrl believes is clean, and is not tracking with its 'limbo' code. To avoid this, the partid and pmg are always read and written as a pair. This requires a new u64 field. In struct task_struct there are two u32, rmid and closid for the x86 case, but as we can't use them here do something else. Add this new field, mpam_partid_pmg, to struct thread_info to avoid adding more architecture specific code to struct task_struct. Always use READ_ONCE()/WRITE_ONCE() when accessing this field. Resctrl allows a per-cpu 'default' value to be set, this overrides the values when scheduling a task in the default control-group, which has PARTID 0. The way 'code data prioritisation' gets emulated means the register value for the default group needs to be a variable. The current system register value is kept in a per-cpu variable to avoid writing to the system register if the value isn't going to change. Writes to this register may reset the hardware state for regulating bandwidth. Finally, there is no reason to context switch these registers unless there is a driver changing the values in struct task_struct. Hide the whole thing behind a static key. This also allows the driver to disable MPAM in response to errors reported by hardware. Move the existing static key to belong to the arch code, as in the future the MPAM driver may become a loadable module. All this should depend on whether there is an MPAM driver, hide it behind CONFIG_ARM64_MPAM. Tested-by: Gavin Shan <gshan@redhat.com> Tested-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com> Tested-by: Peter Newman <peternewman@google.com> Tested-by: Zeng Heng <zengheng4@huawei.com> Tested-by: Punit Agrawal <punit.agrawal@oss.qualcomm.com> Tested-by: Jesse Chick <jessechick@os.amperecomputing.com> CC: Amit Singh Tomar <amitsinght@marvell.com> Reviewed-by: Zeng Heng <zengheng4@huawei.com> Reviewed-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com> Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com> Reviewed-by: Gavin Shan <gshan@redhat.com> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> Co-developed-by: Ben Horgan <ben.horgan@arm.com> Signed-off-by: Ben Horgan <ben.horgan@arm.com> Signed-off-by: James Morse <james.morse@arm.com>
2026-03-13 14:45:43 +00:00
arm_mpam: Register and enable IRQs Register and enable error IRQs. All the MPAM error interrupts indicate a software bug, e.g. out of range partid. If the error interrupt is ever signalled, attempt to disable MPAM. Only the irq handler accesses the MPAMF_ESR register, so no locking is needed. The work to disable MPAM after an error needs to happen at process context as it takes mutex. It also unregisters the interrupts, meaning it can't be done from the threaded part of a threaded interrupt. Instead, mpam_disable() gets scheduled. Enabling the IRQs in the MSC may involve cross calling to a CPU that can access the MSC. Once the IRQ is requested, the mpam_disable() path can be called asynchronously, which will walk structures sized by max_partid. Ensure this size is fixed before the interrupt is requested. CC: Rohit Mathew <rohit.mathew@arm.com> Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com> Reviewed-by: Gavin Shan <gshan@redhat.com> Reviewed-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com> Reviewed-by: Fenghua Yu <fenghuay@nvidia.com> Tested-by: Rohit Mathew <rohit.mathew@arm.com> Tested-by: Fenghua Yu <fenghuay@nvidia.com> Tested-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com> Tested-by: Peter Newman <peternewman@google.com> Tested-by: Carl Worth <carl@os.amperecomputing.com> Tested-by: Gavin Shan <gshan@redhat.com> Tested-by: Zeng Heng <zengheng4@huawei.com> Tested-by: Hanjun Guo <guohanjun@huawei.com> Signed-off-by: James Morse <james.morse@arm.com> Signed-off-by: Ben Horgan <ben.horgan@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
2025-11-19 12:22:51 +00:00
2025-11-19 12:22:48 +00:00
arm_mpam: Add cpuhp callbacks to probe MSC hardware Because an MSC can only by accessed from the CPUs in its cpu-affinity set we need to be running on one of those CPUs to probe the MSC hardware. Do this work in the cpuhp callback. Probing the hardware will only happen before MPAM is enabled, walk all the MSCs and probe those we can reach that haven't already been probed as each CPU's online call is made. This adds the low-level MSC register read accessors. Once all MSCs reported by the firmware have been probed from a CPU in their respective cpu-affinity set, the probe-time cpuhp callbacks are replaced. The replacement callbacks will ultimately need to handle save/restore of the runtime MSC state across power transitions, but for now there is nothing to do in them: so do nothing. The architecture's context switch code will be enabled by a static-key, this can be set by mpam_enable(), but must be done from process context, not a cpuhp callback because both take the cpuhp lock. Whenever a new MSC has been probed, the mpam_enable() work is scheduled to test if all the MSCs have been probed. If probing fails, mpam_disable() is scheduled to unregister the cpuhp callbacks and free memory. CC: Lecopzer Chen <lecopzerc@nvidia.com> Signed-off-by: James Morse <james.morse@arm.com> Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com> Reviewed-by: Ben Horgan <ben.horgan@arm.com> Reviewed-by: Fenghua Yu <fenghuay@nvidia.com> Reviewed-by: Gavin Shan <gshan@redhat.com> Reviewed-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com> Tested-by: Fenghua Yu <fenghuay@nvidia.com> Tested-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com> Tested-by: Peter Newman <peternewman@google.com> Tested-by: Carl Worth <carl@os.amperecomputing.com> Tested-by: Gavin Shan <gshan@redhat.com> Tested-by: Zeng Heng <zengheng4@huawei.com> Tested-by: Hanjun Guo <guohanjun@huawei.com> Signed-off-by: Ben Horgan <ben.horgan@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
2025-11-19 12:22:43 +00:00
arm_mpam: Register and enable IRQs Register and enable error IRQs. All the MPAM error interrupts indicate a software bug, e.g. out of range partid. If the error interrupt is ever signalled, attempt to disable MPAM. Only the irq handler accesses the MPAMF_ESR register, so no locking is needed. The work to disable MPAM after an error needs to happen at process context as it takes mutex. It also unregisters the interrupts, meaning it can't be done from the threaded part of a threaded interrupt. Instead, mpam_disable() gets scheduled. Enabling the IRQs in the MSC may involve cross calling to a CPU that can access the MSC. Once the IRQ is requested, the mpam_disable() path can be called asynchronously, which will walk structures sized by max_partid. Ensure this size is fixed before the interrupt is requested. CC: Rohit Mathew <rohit.mathew@arm.com> Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com> Reviewed-by: Gavin Shan <gshan@redhat.com> Reviewed-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com> Reviewed-by: Fenghua Yu <fenghuay@nvidia.com> Tested-by: Rohit Mathew <rohit.mathew@arm.com> Tested-by: Fenghua Yu <fenghuay@nvidia.com> Tested-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com> Tested-by: Peter Newman <peternewman@google.com> Tested-by: Carl Worth <carl@os.amperecomputing.com> Tested-by: Gavin Shan <gshan@redhat.com> Tested-by: Zeng Heng <zengheng4@huawei.com> Tested-by: Hanjun Guo <guohanjun@huawei.com> Signed-off-by: James Morse <james.morse@arm.com> Signed-off-by: Ben Horgan <ben.horgan@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
2025-11-19 12:22:51 +00:00
arm_mpam: Add helpers for managing the locking around the mon_sel registers The MSC MON_SEL register needs to be accessed from hardirq for the overflow interrupt, and when taking an IPI to access these registers on platforms where MSC are not accessible from every CPU. This makes an irqsave spinlock the obvious lock to protect these registers. On systems with SCMI or PCC mailboxes it must be able to sleep, meaning a mutex must be used. The SCMI or PCC platforms can't support an overflow interrupt, and can't access the registers from hardirq context. Clearly these two can't exist for one MSC at the same time. Add helpers for the MON_SEL locking. For now, use a irqsave spinlock and only support 'real' MMIO platforms. In the future this lock will be split in two allowing SCMI/PCC platforms to take a mutex. Because there are contexts where the SCMI/PCC platforms can't make an access, mpam_mon_sel_lock() needs to be able to fail. Do this now, so that all the error handling on these paths is present. This allows the relevant paths to fail if they are needed on a platform where this isn't possible, instead of having to make explicit checks of the interface type. Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com> Reviewed-by: Gavin Shan <gshan@redhat.com> Reviewed-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com> Reviewed-by: Fenghua Yu <fenghuay@nvidia.com> Tested-by: Fenghua Yu <fenghuay@nvidia.com> Tested-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com> Tested-by: Peter Newman <peternewman@google.com> Tested-by: Carl Worth <carl@os.amperecomputing.com> Tested-by: Gavin Shan <gshan@redhat.com> Tested-by: Zeng Heng <zengheng4@huawei.com> Tested-by: Hanjun Guo <guohanjun@huawei.com> Signed-off-by: James Morse <james.morse@arm.com> Signed-off-by: Ben Horgan <ben.horgan@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
2025-11-19 12:22:45 +00:00
arm_mpam: Add workaround for T241-MPAM-1 The MPAM bandwidth partitioning controls will not be correctly configured, and hardware will retain default configuration register values, meaning generally that bandwidth will remain unprovisioned. To address the issue, follow the below steps after updating the MBW_MIN and/or MBW_MAX registers. - Perform 64b reads from all 12 bridge MPAM shadow registers at offsets (0x360048 + slice*0x10000 + partid*8). These registers are read-only. - Continue iterating until all 12 shadow register values match in a loop. pr_warn_once if the values fail to match within the loop count 1000. - Perform 64b writes with the value 0x0 to the two spare registers at offsets 0x1b0000 and 0x1c0000. In the hardware, writes to the MPAMCFG_MBW_MAX MPAMCFG_MBW_MIN registers are transformed into broadcast writes to the 12 shadow registers. The final two writes to the spare registers cause a final rank of downstream micro-architectural MPAM registers to be updated from the shadow copies. The intervening loop to read the 12 shadow registers helps avoid a race condition where writes to the spare registers occur before all shadow registers have been updated. Tested-by: Gavin Shan <gshan@redhat.com> Tested-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com> Tested-by: Punit Agrawal <punit.agrawal@oss.qualcomm.com> Tested-by: Jesse Chick <jessechick@os.amperecomputing.com> Reviewed-by: Zeng Heng <zengheng4@huawei.com> Reviewed-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com> Reviewed-by: Gavin Shan <gshan@redhat.com> Signed-off-by: Shanker Donthineni <sdonthineni@nvidia.com> Signed-off-by: Ben Horgan <ben.horgan@arm.com> Signed-off-by: James Morse <james.morse@arm.com>
2026-03-13 14:46:13 +00:00
arm_mpam: Add helpers for managing the locking around the mon_sel registers The MSC MON_SEL register needs to be accessed from hardirq for the overflow interrupt, and when taking an IPI to access these registers on platforms where MSC are not accessible from every CPU. This makes an irqsave spinlock the obvious lock to protect these registers. On systems with SCMI or PCC mailboxes it must be able to sleep, meaning a mutex must be used. The SCMI or PCC platforms can't support an overflow interrupt, and can't access the registers from hardirq context. Clearly these two can't exist for one MSC at the same time. Add helpers for the MON_SEL locking. For now, use a irqsave spinlock and only support 'real' MMIO platforms. In the future this lock will be split in two allowing SCMI/PCC platforms to take a mutex. Because there are contexts where the SCMI/PCC platforms can't make an access, mpam_mon_sel_lock() needs to be able to fail. Do this now, so that all the error handling on these paths is present. This allows the relevant paths to fail if they are needed on a platform where this isn't possible, instead of having to make explicit checks of the interface type. Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com> Reviewed-by: Gavin Shan <gshan@redhat.com> Reviewed-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com> Reviewed-by: Fenghua Yu <fenghuay@nvidia.com> Tested-by: Fenghua Yu <fenghuay@nvidia.com> Tested-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com> Tested-by: Peter Newman <peternewman@google.com> Tested-by: Carl Worth <carl@os.amperecomputing.com> Tested-by: Gavin Shan <gshan@redhat.com> Tested-by: Zeng Heng <zengheng4@huawei.com> Tested-by: Hanjun Guo <guohanjun@huawei.com> Signed-off-by: James Morse <james.morse@arm.com> Signed-off-by: Ben Horgan <ben.horgan@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
2025-11-19 12:22:45 +00:00
arm_mpam: Add workaround for T241-MPAM-1 The MPAM bandwidth partitioning controls will not be correctly configured, and hardware will retain default configuration register values, meaning generally that bandwidth will remain unprovisioned. To address the issue, follow the below steps after updating the MBW_MIN and/or MBW_MAX registers. - Perform 64b reads from all 12 bridge MPAM shadow registers at offsets (0x360048 + slice*0x10000 + partid*8). These registers are read-only. - Continue iterating until all 12 shadow register values match in a loop. pr_warn_once if the values fail to match within the loop count 1000. - Perform 64b writes with the value 0x0 to the two spare registers at offsets 0x1b0000 and 0x1c0000. In the hardware, writes to the MPAMCFG_MBW_MAX MPAMCFG_MBW_MIN registers are transformed into broadcast writes to the 12 shadow registers. The final two writes to the spare registers cause a final rank of downstream micro-architectural MPAM registers to be updated from the shadow copies. The intervening loop to read the 12 shadow registers helps avoid a race condition where writes to the spare registers occur before all shadow registers have been updated. Tested-by: Gavin Shan <gshan@redhat.com> Tested-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com> Tested-by: Punit Agrawal <punit.agrawal@oss.qualcomm.com> Tested-by: Jesse Chick <jessechick@os.amperecomputing.com> Reviewed-by: Zeng Heng <zengheng4@huawei.com> Reviewed-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com> Reviewed-by: Gavin Shan <gshan@redhat.com> Signed-off-by: Shanker Donthineni <sdonthineni@nvidia.com> Signed-off-by: Ben Horgan <ben.horgan@arm.com> Signed-off-by: James Morse <james.morse@arm.com>
2026-03-13 14:46:13 +00:00
arm_mpam: Add workaround for T241-MPAM-4 In the T241 implementation of memory-bandwidth partitioning, in the absence of contention for bandwidth, the minimum bandwidth setting can affect the amount of achieved bandwidth. Specifically, the achieved bandwidth in the absence of contention can settle to any value between the values of MPAMCFG_MBW_MIN and MPAMCFG_MBW_MAX. Also, if MPAMCFG_MBW_MIN is set zero (below 0.78125%), once a core enters a throttled state, it will never leave that state. The first issue is not a concern if the MPAM software allows to program MPAMCFG_MBW_MIN through the sysfs interface. This patch ensures program MBW_MIN=1 (0.78125%) whenever MPAMCFG_MBW_MIN=0 is programmed. In the scenario where the resctrl doesn't support the MBW_MIN interface via sysfs, to achieve bandwidth closer to MBW_MAX in the absence of contention, software should configure a relatively narrow gap between MBW_MIN and MBW_MAX. The recommendation is to use a 5% gap to mitigate the problem. Clear the feature MBW_MIN feature from the class to ensure we don't accidentally change behaviour when resctrl adds support for a MBW_MIN interface. Tested-by: Gavin Shan <gshan@redhat.com> Tested-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com> Tested-by: Jesse Chick <jessechick@os.amperecomputing.com> Reviewed-by: Zeng Heng <zengheng4@huawei.com> Reviewed-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com> Reviewed-by: Fenghua Yu <fenghuay@nvidia.com> Reviewed-by: Gavin Shan <gshan@redhat.com> Signed-off-by: Shanker Donthineni <sdonthineni@nvidia.com> Signed-off-by: Ben Horgan <ben.horgan@arm.com> Signed-off-by: James Morse <james.morse@arm.com>
2026-03-13 14:46:14 +00:00
arm_mpam: Add workaround for T241-MPAM-1 The MPAM bandwidth partitioning controls will not be correctly configured, and hardware will retain default configuration register values, meaning generally that bandwidth will remain unprovisioned. To address the issue, follow the below steps after updating the MBW_MIN and/or MBW_MAX registers. - Perform 64b reads from all 12 bridge MPAM shadow registers at offsets (0x360048 + slice*0x10000 + partid*8). These registers are read-only. - Continue iterating until all 12 shadow register values match in a loop. pr_warn_once if the values fail to match within the loop count 1000. - Perform 64b writes with the value 0x0 to the two spare registers at offsets 0x1b0000 and 0x1c0000. In the hardware, writes to the MPAMCFG_MBW_MAX MPAMCFG_MBW_MIN registers are transformed into broadcast writes to the 12 shadow registers. The final two writes to the spare registers cause a final rank of downstream micro-architectural MPAM registers to be updated from the shadow copies. The intervening loop to read the 12 shadow registers helps avoid a race condition where writes to the spare registers occur before all shadow registers have been updated. Tested-by: Gavin Shan <gshan@redhat.com> Tested-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com> Tested-by: Punit Agrawal <punit.agrawal@oss.qualcomm.com> Tested-by: Jesse Chick <jessechick@os.amperecomputing.com> Reviewed-by: Zeng Heng <zengheng4@huawei.com> Reviewed-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com> Reviewed-by: Gavin Shan <gshan@redhat.com> Signed-off-by: Shanker Donthineni <sdonthineni@nvidia.com> Signed-off-by: Ben Horgan <ben.horgan@arm.com> Signed-off-by: James Morse <james.morse@arm.com>
2026-03-13 14:46:13 +00:00
2025-11-19 12:22:48 +00:00
arm_mpam: resctrl: Add CDP emulation Intel RDT's CDP feature allows the cache to use a different control value depending on whether the accesses was for instruction fetch or a data access. MPAM's equivalent feature is the other way up: the CPU assigns a different partid label to traffic depending on whether it was instruction fetch or a data access, which causes the cache to use a different control value based solely on the partid. MPAM can emulate CDP, with the side effect that the alternative partid is seen by all MSC, it can't be enabled per-MSC. Add the resctrl hooks to turn this on or off. Add the helpers that match a closid against a task, which need to be aware that the value written to hardware is not the same as the one resctrl is using. Update the 'arm64_mpam_global_default' variable the arch code uses during context switch to know when the per-cpu value should be used instead. Also, update these per-cpu values and sync the resulting mpam partid/pmg configuration to hardware. resctrl can enable CDP for L2 caches, L3 caches or both. When it is enabled by one and not the other MPAM globally enabled CDP but hides the effect on the other cache resource. This hiding is possible as CPOR is the only supported cache control and that uses a resource bitmap; two partids with the same bitmap act as one. Awkwardly, the MB controls don't implement CDP and CDP can't be hidden as the memory bandwidth control is a maximum per partid which can't be modelled with more partids. If the total maximum is used for both the data and instruction partids then then the maximum may be exceeded and if it is split in two then the one using more bandwidth will hit a lower limit. Hence, hide the MB controls completely if CDP is enabled for any resource. Tested-by: Gavin Shan <gshan@redhat.com> Tested-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com> Tested-by: Peter Newman <peternewman@google.com> Tested-by: Zeng Heng <zengheng4@huawei.com> Tested-by: Punit Agrawal <punit.agrawal@oss.qualcomm.com> Tested-by: Jesse Chick <jessechick@os.amperecomputing.com> Cc: Dave Martin <Dave.Martin@arm.com> Cc: Amit Singh Tomar <amitsinght@marvell.com> Reviewed-by: Zeng Heng <zengheng4@huawei.com> Reviewed-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com> Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com> Reviewed-by: Gavin Shan <gshan@redhat.com> Co-developed-by: Ben Horgan <ben.horgan@arm.com> Signed-off-by: Ben Horgan <ben.horgan@arm.com> Signed-off-by: James Morse <james.morse@arm.com>
2026-03-13 14:45:57 +00:00
arm_mpam: Add cpuhp callbacks to probe MSC hardware Because an MSC can only by accessed from the CPUs in its cpu-affinity set we need to be running on one of those CPUs to probe the MSC hardware. Do this work in the cpuhp callback. Probing the hardware will only happen before MPAM is enabled, walk all the MSCs and probe those we can reach that haven't already been probed as each CPU's online call is made. This adds the low-level MSC register read accessors. Once all MSCs reported by the firmware have been probed from a CPU in their respective cpu-affinity set, the probe-time cpuhp callbacks are replaced. The replacement callbacks will ultimately need to handle save/restore of the runtime MSC state across power transitions, but for now there is nothing to do in them: so do nothing. The architecture's context switch code will be enabled by a static-key, this can be set by mpam_enable(), but must be done from process context, not a cpuhp callback because both take the cpuhp lock. Whenever a new MSC has been probed, the mpam_enable() work is scheduled to test if all the MSCs have been probed. If probing fails, mpam_disable() is scheduled to unregister the cpuhp callbacks and free memory. CC: Lecopzer Chen <lecopzerc@nvidia.com> Signed-off-by: James Morse <james.morse@arm.com> Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com> Reviewed-by: Ben Horgan <ben.horgan@arm.com> Reviewed-by: Fenghua Yu <fenghuay@nvidia.com> Reviewed-by: Gavin Shan <gshan@redhat.com> Reviewed-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com> Tested-by: Fenghua Yu <fenghuay@nvidia.com> Tested-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com> Tested-by: Peter Newman <peternewman@google.com> Tested-by: Carl Worth <carl@os.amperecomputing.com> Tested-by: Gavin Shan <gshan@redhat.com> Tested-by: Zeng Heng <zengheng4@huawei.com> Tested-by: Hanjun Guo <guohanjun@huawei.com> Signed-off-by: Ben Horgan <ben.horgan@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
2025-11-19 12:22:43 +00:00