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6d3b47ddff
A CPU's current task can have its {closid, rmid} fields read locally
while they are being concurrently written to from another CPU.
This can happen anytime __resctrl_sched_in() races with either
__rdtgroup_move_task() or rdt_move_group_tasks().
Prevent load / store tearing for those accesses by giving them the
READ_ONCE() / WRITE_ONCE() treatment.
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/9921fda88ad81afb9885b517fbe864a2bc7c35a9.1608243147.git.reinette.chatre@intel.com
99 lines
2.7 KiB
C
99 lines
2.7 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _ASM_X86_RESCTRL_H
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#define _ASM_X86_RESCTRL_H
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#ifdef CONFIG_X86_CPU_RESCTRL
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#include <linux/sched.h>
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#include <linux/jump_label.h>
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#define IA32_PQR_ASSOC 0x0c8f
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/**
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* struct resctrl_pqr_state - State cache for the PQR MSR
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* @cur_rmid: The cached Resource Monitoring ID
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* @cur_closid: The cached Class Of Service ID
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* @default_rmid: The user assigned Resource Monitoring ID
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* @default_closid: The user assigned cached Class Of Service ID
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*
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* The upper 32 bits of IA32_PQR_ASSOC contain closid and the
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* lower 10 bits rmid. The update to IA32_PQR_ASSOC always
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* contains both parts, so we need to cache them. This also
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* stores the user configured per cpu CLOSID and RMID.
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*
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* The cache also helps to avoid pointless updates if the value does
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* not change.
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*/
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struct resctrl_pqr_state {
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u32 cur_rmid;
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u32 cur_closid;
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u32 default_rmid;
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u32 default_closid;
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};
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DECLARE_PER_CPU(struct resctrl_pqr_state, pqr_state);
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DECLARE_STATIC_KEY_FALSE(rdt_enable_key);
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DECLARE_STATIC_KEY_FALSE(rdt_alloc_enable_key);
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DECLARE_STATIC_KEY_FALSE(rdt_mon_enable_key);
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/*
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* __resctrl_sched_in() - Writes the task's CLOSid/RMID to IA32_PQR_MSR
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*
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* Following considerations are made so that this has minimal impact
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* on scheduler hot path:
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* - This will stay as no-op unless we are running on an Intel SKU
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* which supports resource control or monitoring and we enable by
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* mounting the resctrl file system.
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* - Caches the per cpu CLOSid/RMID values and does the MSR write only
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* when a task with a different CLOSid/RMID is scheduled in.
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* - We allocate RMIDs/CLOSids globally in order to keep this as
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* simple as possible.
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* Must be called with preemption disabled.
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*/
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static void __resctrl_sched_in(void)
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{
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struct resctrl_pqr_state *state = this_cpu_ptr(&pqr_state);
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u32 closid = state->default_closid;
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u32 rmid = state->default_rmid;
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u32 tmp;
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/*
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* If this task has a closid/rmid assigned, use it.
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* Else use the closid/rmid assigned to this cpu.
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*/
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if (static_branch_likely(&rdt_alloc_enable_key)) {
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tmp = READ_ONCE(current->closid);
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if (tmp)
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closid = tmp;
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}
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if (static_branch_likely(&rdt_mon_enable_key)) {
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tmp = READ_ONCE(current->rmid);
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if (tmp)
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rmid = tmp;
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}
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if (closid != state->cur_closid || rmid != state->cur_rmid) {
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state->cur_closid = closid;
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state->cur_rmid = rmid;
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wrmsr(IA32_PQR_ASSOC, rmid, closid);
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}
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}
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static inline void resctrl_sched_in(void)
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{
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if (static_branch_likely(&rdt_enable_key))
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__resctrl_sched_in();
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}
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void resctrl_cpu_detect(struct cpuinfo_x86 *c);
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#else
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static inline void resctrl_sched_in(void) {}
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static inline void resctrl_cpu_detect(struct cpuinfo_x86 *c) {}
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#endif /* CONFIG_X86_CPU_RESCTRL */
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#endif /* _ASM_X86_RESCTRL_H */
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