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1/*
2 * Copyright (C) 1995 Linus Torvalds
3 *
4 * Pentium III FXSR, SSE support
5 * Gareth Hughes <gareth@valinux.com>, May 2000
6 */
7
8/*
9 * This file handles the architecture-dependent parts of process handling..
10 */
11
12#include <linux/cpu.h>
13#include <linux/errno.h>
14#include <linux/sched.h>
15#include <linux/fs.h>
16#include <linux/kernel.h>
17#include <linux/mm.h>
18#include <linux/elfcore.h>
19#include <linux/smp.h>
20#include <linux/stddef.h>
21#include <linux/slab.h>
22#include <linux/vmalloc.h>
23#include <linux/user.h>
24#include <linux/interrupt.h>
25#include <linux/delay.h>
26#include <linux/reboot.h>
27#include <linux/mc146818rtc.h>
28#include <linux/module.h>
29#include <linux/kallsyms.h>
30#include <linux/ptrace.h>
31#include <linux/personality.h>
32#include <linux/percpu.h>
33#include <linux/prctl.h>
34#include <linux/ftrace.h>
35#include <linux/uaccess.h>
36#include <linux/io.h>
37#include <linux/kdebug.h>
38
39#include <asm/pgtable.h>
40#include <asm/ldt.h>
41#include <asm/processor.h>
42#include <asm/i387.h>
43#include <asm/fpu-internal.h>
44#include <asm/desc.h>
45#ifdef CONFIG_MATH_EMULATION
46#include <asm/math_emu.h>
47#endif
48
49#include <linux/err.h>
50
51#include <asm/tlbflush.h>
52#include <asm/cpu.h>
53#include <asm/idle.h>
54#include <asm/syscalls.h>
55#include <asm/debugreg.h>
56#include <asm/switch_to.h>
57
58asmlinkage void ret_from_fork(void) __asm__("ret_from_fork");
59asmlinkage void ret_from_kernel_thread(void) __asm__("ret_from_kernel_thread");
60
61/*
62 * Return saved PC of a blocked thread.
63 */
64unsigned long thread_saved_pc(struct task_struct *tsk)
65{
66 return ((unsigned long *)tsk->thread.sp)[3];
67}
68
69void __show_regs(struct pt_regs *regs, int all)
70{
71 unsigned long cr0 = 0L, cr2 = 0L, cr3 = 0L, cr4 = 0L;
72 unsigned long d0, d1, d2, d3, d6, d7;
73 unsigned long sp;
74 unsigned short ss, gs;
75
76 if (user_mode_vm(regs)) {
77 sp = regs->sp;
78 ss = regs->ss & 0xffff;
79 gs = get_user_gs(regs);
80 } else {
81 sp = kernel_stack_pointer(regs);
82 savesegment(ss, ss);
83 savesegment(gs, gs);
84 }
85
86 printk(KERN_DEFAULT "EIP: %04x:[<%08lx>] EFLAGS: %08lx CPU: %d\n",
87 (u16)regs->cs, regs->ip, regs->flags,
88 smp_processor_id());
89 print_symbol("EIP is at %s\n", regs->ip);
90
91 printk(KERN_DEFAULT "EAX: %08lx EBX: %08lx ECX: %08lx EDX: %08lx\n",
92 regs->ax, regs->bx, regs->cx, regs->dx);
93 printk(KERN_DEFAULT "ESI: %08lx EDI: %08lx EBP: %08lx ESP: %08lx\n",
94 regs->si, regs->di, regs->bp, sp);
95 printk(KERN_DEFAULT " DS: %04x ES: %04x FS: %04x GS: %04x SS: %04x\n",
96 (u16)regs->ds, (u16)regs->es, (u16)regs->fs, gs, ss);
97
98 if (!all)
99 return;
100
101 cr0 = read_cr0();
102 cr2 = read_cr2();
103 cr3 = read_cr3();
104 cr4 = read_cr4_safe();
105 printk(KERN_DEFAULT "CR0: %08lx CR2: %08lx CR3: %08lx CR4: %08lx\n",
106 cr0, cr2, cr3, cr4);
107
108 get_debugreg(d0, 0);
109 get_debugreg(d1, 1);
110 get_debugreg(d2, 2);
111 get_debugreg(d3, 3);
112 get_debugreg(d6, 6);
113 get_debugreg(d7, 7);
114
115 /* Only print out debug registers if they are in their non-default state. */
116 if ((d0 == 0) && (d1 == 0) && (d2 == 0) && (d3 == 0) &&
117 (d6 == DR6_RESERVED) && (d7 == 0x400))
118 return;
119
120 printk(KERN_DEFAULT "DR0: %08lx DR1: %08lx DR2: %08lx DR3: %08lx\n",
121 d0, d1, d2, d3);
122 printk(KERN_DEFAULT "DR6: %08lx DR7: %08lx\n",
123 d6, d7);
124}
125
126void release_thread(struct task_struct *dead_task)
127{
128 BUG_ON(dead_task->mm);
129 release_vm86_irqs(dead_task);
130}
131
132int copy_thread(unsigned long clone_flags, unsigned long sp,
133 unsigned long arg, struct task_struct *p)
134{
135 struct pt_regs *childregs = task_pt_regs(p);
136 struct task_struct *tsk;
137 int err;
138
139 p->thread.sp = (unsigned long) childregs;
140 p->thread.sp0 = (unsigned long) (childregs+1);
141
142 if (unlikely(p->flags & PF_KTHREAD)) {
143 /* kernel thread */
144 memset(childregs, 0, sizeof(struct pt_regs));
145 p->thread.ip = (unsigned long) ret_from_kernel_thread;
146 task_user_gs(p) = __KERNEL_STACK_CANARY;
147 childregs->ds = __USER_DS;
148 childregs->es = __USER_DS;
149 childregs->fs = __KERNEL_PERCPU;
150 childregs->bx = sp; /* function */
151 childregs->bp = arg;
152 childregs->orig_ax = -1;
153 childregs->cs = __KERNEL_CS | get_kernel_rpl();
154 childregs->flags = X86_EFLAGS_IF | X86_EFLAGS_FIXED;
155 p->thread.fpu_counter = 0;
156 p->thread.io_bitmap_ptr = NULL;
157 memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps));
158 return 0;
159 }
160 *childregs = *current_pt_regs();
161 childregs->ax = 0;
162 if (sp)
163 childregs->sp = sp;
164
165 p->thread.ip = (unsigned long) ret_from_fork;
166 task_user_gs(p) = get_user_gs(current_pt_regs());
167
168 p->thread.fpu_counter = 0;
169 p->thread.io_bitmap_ptr = NULL;
170 tsk = current;
171 err = -ENOMEM;
172
173 memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps));
174
175 if (unlikely(test_tsk_thread_flag(tsk, TIF_IO_BITMAP))) {
176 p->thread.io_bitmap_ptr = kmemdup(tsk->thread.io_bitmap_ptr,
177 IO_BITMAP_BYTES, GFP_KERNEL);
178 if (!p->thread.io_bitmap_ptr) {
179 p->thread.io_bitmap_max = 0;
180 return -ENOMEM;
181 }
182 set_tsk_thread_flag(p, TIF_IO_BITMAP);
183 }
184
185 err = 0;
186
187 /*
188 * Set a new TLS for the child thread?
189 */
190 if (clone_flags & CLONE_SETTLS)
191 err = do_set_thread_area(p, -1,
192 (struct user_desc __user *)childregs->si, 0);
193
194 if (err && p->thread.io_bitmap_ptr) {
195 kfree(p->thread.io_bitmap_ptr);
196 p->thread.io_bitmap_max = 0;
197 }
198 return err;
199}
200
201void
202start_thread(struct pt_regs *regs, unsigned long new_ip, unsigned long new_sp)
203{
204 set_user_gs(regs, 0);
205 regs->fs = 0;
206 regs->ds = __USER_DS;
207 regs->es = __USER_DS;
208 regs->ss = __USER_DS;
209 regs->cs = __USER_CS;
210 regs->ip = new_ip;
211 regs->sp = new_sp;
212 regs->flags = X86_EFLAGS_IF;
213 /*
214 * force it to the iret return path by making it look as if there was
215 * some work pending.
216 */
217 set_thread_flag(TIF_NOTIFY_RESUME);
218}
219EXPORT_SYMBOL_GPL(start_thread);
220
221
222/*
223 * switch_to(x,y) should switch tasks from x to y.
224 *
225 * We fsave/fwait so that an exception goes off at the right time
226 * (as a call from the fsave or fwait in effect) rather than to
227 * the wrong process. Lazy FP saving no longer makes any sense
228 * with modern CPU's, and this simplifies a lot of things (SMP
229 * and UP become the same).
230 *
231 * NOTE! We used to use the x86 hardware context switching. The
232 * reason for not using it any more becomes apparent when you
233 * try to recover gracefully from saved state that is no longer
234 * valid (stale segment register values in particular). With the
235 * hardware task-switch, there is no way to fix up bad state in
236 * a reasonable manner.
237 *
238 * The fact that Intel documents the hardware task-switching to
239 * be slow is a fairly red herring - this code is not noticeably
240 * faster. However, there _is_ some room for improvement here,
241 * so the performance issues may eventually be a valid point.
242 * More important, however, is the fact that this allows us much
243 * more flexibility.
244 *
245 * The return value (in %ax) will be the "prev" task after
246 * the task-switch, and shows up in ret_from_fork in entry.S,
247 * for example.
248 */
249__visible __notrace_funcgraph struct task_struct *
250__switch_to(struct task_struct *prev_p, struct task_struct *next_p)
251{
252 struct thread_struct *prev = &prev_p->thread,
253 *next = &next_p->thread;
254 int cpu = smp_processor_id();
255 struct tss_struct *tss = &per_cpu(init_tss, cpu);
256 fpu_switch_t fpu;
257
258 /* never put a printk in __switch_to... printk() calls wake_up*() indirectly */
259
260 fpu = switch_fpu_prepare(prev_p, next_p, cpu);
261
262 /*
263 * Reload esp0.
264 */
265 load_sp0(tss, next);
266
267 /*
268 * Save away %gs. No need to save %fs, as it was saved on the
269 * stack on entry. No need to save %es and %ds, as those are
270 * always kernel segments while inside the kernel. Doing this
271 * before setting the new TLS descriptors avoids the situation
272 * where we temporarily have non-reloadable segments in %fs
273 * and %gs. This could be an issue if the NMI handler ever
274 * used %fs or %gs (it does not today), or if the kernel is
275 * running inside of a hypervisor layer.
276 */
277 lazy_save_gs(prev->gs);
278
279 /*
280 * Load the per-thread Thread-Local Storage descriptor.
281 */
282 load_TLS(next, cpu);
283
284 /*
285 * Restore IOPL if needed. In normal use, the flags restore
286 * in the switch assembly will handle this. But if the kernel
287 * is running virtualized at a non-zero CPL, the popf will
288 * not restore flags, so it must be done in a separate step.
289 */
290 if (get_kernel_rpl() && unlikely(prev->iopl != next->iopl))
291 set_iopl_mask(next->iopl);
292
293 /*
294 * If it were not for PREEMPT_ACTIVE we could guarantee that the
295 * preempt_count of all tasks was equal here and this would not be
296 * needed.
297 */
298 task_thread_info(prev_p)->saved_preempt_count = this_cpu_read(__preempt_count);
299 this_cpu_write(__preempt_count, task_thread_info(next_p)->saved_preempt_count);
300
301 /*
302 * Now maybe handle debug registers and/or IO bitmaps
303 */
304 if (unlikely(task_thread_info(prev_p)->flags & _TIF_WORK_CTXSW_PREV ||
305 task_thread_info(next_p)->flags & _TIF_WORK_CTXSW_NEXT))
306 __switch_to_xtra(prev_p, next_p, tss);
307
308 /*
309 * Leave lazy mode, flushing any hypercalls made here.
310 * This must be done before restoring TLS segments so
311 * the GDT and LDT are properly updated, and must be
312 * done before math_state_restore, so the TS bit is up
313 * to date.
314 */
315 arch_end_context_switch(next_p);
316
317 this_cpu_write(kernel_stack,
318 (unsigned long)task_stack_page(next_p) +
319 THREAD_SIZE - KERNEL_STACK_OFFSET);
320
321 /*
322 * Restore %gs if needed (which is common)
323 */
324 if (prev->gs | next->gs)
325 lazy_load_gs(next->gs);
326
327 switch_fpu_finish(next_p, fpu);
328
329 this_cpu_write(current_task, next_p);
330
331 return prev_p;
332}
333
334#define top_esp (THREAD_SIZE - sizeof(unsigned long))
335#define top_ebp (THREAD_SIZE - 2*sizeof(unsigned long))
336
337unsigned long get_wchan(struct task_struct *p)
338{
339 unsigned long bp, sp, ip;
340 unsigned long stack_page;
341 int count = 0;
342 if (!p || p == current || p->state == TASK_RUNNING)
343 return 0;
344 stack_page = (unsigned long)task_stack_page(p);
345 sp = p->thread.sp;
346 if (!stack_page || sp < stack_page || sp > top_esp+stack_page)
347 return 0;
348 /* include/asm-i386/system.h:switch_to() pushes bp last. */
349 bp = *(unsigned long *) sp;
350 do {
351 if (bp < stack_page || bp > top_ebp+stack_page)
352 return 0;
353 ip = *(unsigned long *) (bp+4);
354 if (!in_sched_functions(ip))
355 return ip;
356 bp = *(unsigned long *) bp;
357 } while (count++ < 16);
358 return 0;
359}
360
1/*
2 * Copyright (C) 1995 Linus Torvalds
3 *
4 * Pentium III FXSR, SSE support
5 * Gareth Hughes <gareth@valinux.com>, May 2000
6 */
7
8/*
9 * This file handles the architecture-dependent parts of process handling..
10 */
11
12#include <linux/cpu.h>
13#include <linux/errno.h>
14#include <linux/sched.h>
15#include <linux/fs.h>
16#include <linux/kernel.h>
17#include <linux/mm.h>
18#include <linux/elfcore.h>
19#include <linux/smp.h>
20#include <linux/stddef.h>
21#include <linux/slab.h>
22#include <linux/vmalloc.h>
23#include <linux/user.h>
24#include <linux/interrupt.h>
25#include <linux/delay.h>
26#include <linux/reboot.h>
27#include <linux/mc146818rtc.h>
28#include <linux/export.h>
29#include <linux/kallsyms.h>
30#include <linux/ptrace.h>
31#include <linux/personality.h>
32#include <linux/percpu.h>
33#include <linux/prctl.h>
34#include <linux/ftrace.h>
35#include <linux/uaccess.h>
36#include <linux/io.h>
37#include <linux/kdebug.h>
38
39#include <asm/pgtable.h>
40#include <asm/ldt.h>
41#include <asm/processor.h>
42#include <asm/fpu/internal.h>
43#include <asm/desc.h>
44#ifdef CONFIG_MATH_EMULATION
45#include <asm/math_emu.h>
46#endif
47
48#include <linux/err.h>
49
50#include <asm/tlbflush.h>
51#include <asm/cpu.h>
52#include <asm/syscalls.h>
53#include <asm/debugreg.h>
54#include <asm/switch_to.h>
55#include <asm/vm86.h>
56#include <asm/intel_rdt.h>
57
58void __show_regs(struct pt_regs *regs, int all)
59{
60 unsigned long cr0 = 0L, cr2 = 0L, cr3 = 0L, cr4 = 0L;
61 unsigned long d0, d1, d2, d3, d6, d7;
62 unsigned long sp;
63 unsigned short ss, gs;
64
65 if (user_mode(regs)) {
66 sp = regs->sp;
67 ss = regs->ss & 0xffff;
68 gs = get_user_gs(regs);
69 } else {
70 sp = kernel_stack_pointer(regs);
71 savesegment(ss, ss);
72 savesegment(gs, gs);
73 }
74
75 printk(KERN_DEFAULT "EIP: %pS\n", (void *)regs->ip);
76 printk(KERN_DEFAULT "EFLAGS: %08lx CPU: %d\n", regs->flags,
77 smp_processor_id());
78
79 printk(KERN_DEFAULT "EAX: %08lx EBX: %08lx ECX: %08lx EDX: %08lx\n",
80 regs->ax, regs->bx, regs->cx, regs->dx);
81 printk(KERN_DEFAULT "ESI: %08lx EDI: %08lx EBP: %08lx ESP: %08lx\n",
82 regs->si, regs->di, regs->bp, sp);
83 printk(KERN_DEFAULT " DS: %04x ES: %04x FS: %04x GS: %04x SS: %04x\n",
84 (u16)regs->ds, (u16)regs->es, (u16)regs->fs, gs, ss);
85
86 if (!all)
87 return;
88
89 cr0 = read_cr0();
90 cr2 = read_cr2();
91 cr3 = read_cr3();
92 cr4 = __read_cr4();
93 printk(KERN_DEFAULT "CR0: %08lx CR2: %08lx CR3: %08lx CR4: %08lx\n",
94 cr0, cr2, cr3, cr4);
95
96 get_debugreg(d0, 0);
97 get_debugreg(d1, 1);
98 get_debugreg(d2, 2);
99 get_debugreg(d3, 3);
100 get_debugreg(d6, 6);
101 get_debugreg(d7, 7);
102
103 /* Only print out debug registers if they are in their non-default state. */
104 if ((d0 == 0) && (d1 == 0) && (d2 == 0) && (d3 == 0) &&
105 (d6 == DR6_RESERVED) && (d7 == 0x400))
106 return;
107
108 printk(KERN_DEFAULT "DR0: %08lx DR1: %08lx DR2: %08lx DR3: %08lx\n",
109 d0, d1, d2, d3);
110 printk(KERN_DEFAULT "DR6: %08lx DR7: %08lx\n",
111 d6, d7);
112}
113
114void release_thread(struct task_struct *dead_task)
115{
116 BUG_ON(dead_task->mm);
117 release_vm86_irqs(dead_task);
118}
119
120int copy_thread_tls(unsigned long clone_flags, unsigned long sp,
121 unsigned long arg, struct task_struct *p, unsigned long tls)
122{
123 struct pt_regs *childregs = task_pt_regs(p);
124 struct fork_frame *fork_frame = container_of(childregs, struct fork_frame, regs);
125 struct inactive_task_frame *frame = &fork_frame->frame;
126 struct task_struct *tsk;
127 int err;
128
129 frame->bp = 0;
130 frame->ret_addr = (unsigned long) ret_from_fork;
131 p->thread.sp = (unsigned long) fork_frame;
132 p->thread.sp0 = (unsigned long) (childregs+1);
133 memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps));
134
135 if (unlikely(p->flags & PF_KTHREAD)) {
136 /* kernel thread */
137 memset(childregs, 0, sizeof(struct pt_regs));
138 frame->bx = sp; /* function */
139 frame->di = arg;
140 p->thread.io_bitmap_ptr = NULL;
141 return 0;
142 }
143 frame->bx = 0;
144 *childregs = *current_pt_regs();
145 childregs->ax = 0;
146 if (sp)
147 childregs->sp = sp;
148
149 task_user_gs(p) = get_user_gs(current_pt_regs());
150
151 p->thread.io_bitmap_ptr = NULL;
152 tsk = current;
153 err = -ENOMEM;
154
155 if (unlikely(test_tsk_thread_flag(tsk, TIF_IO_BITMAP))) {
156 p->thread.io_bitmap_ptr = kmemdup(tsk->thread.io_bitmap_ptr,
157 IO_BITMAP_BYTES, GFP_KERNEL);
158 if (!p->thread.io_bitmap_ptr) {
159 p->thread.io_bitmap_max = 0;
160 return -ENOMEM;
161 }
162 set_tsk_thread_flag(p, TIF_IO_BITMAP);
163 }
164
165 err = 0;
166
167 /*
168 * Set a new TLS for the child thread?
169 */
170 if (clone_flags & CLONE_SETTLS)
171 err = do_set_thread_area(p, -1,
172 (struct user_desc __user *)tls, 0);
173
174 if (err && p->thread.io_bitmap_ptr) {
175 kfree(p->thread.io_bitmap_ptr);
176 p->thread.io_bitmap_max = 0;
177 }
178 return err;
179}
180
181void
182start_thread(struct pt_regs *regs, unsigned long new_ip, unsigned long new_sp)
183{
184 set_user_gs(regs, 0);
185 regs->fs = 0;
186 regs->ds = __USER_DS;
187 regs->es = __USER_DS;
188 regs->ss = __USER_DS;
189 regs->cs = __USER_CS;
190 regs->ip = new_ip;
191 regs->sp = new_sp;
192 regs->flags = X86_EFLAGS_IF;
193 force_iret();
194}
195EXPORT_SYMBOL_GPL(start_thread);
196
197
198/*
199 * switch_to(x,y) should switch tasks from x to y.
200 *
201 * We fsave/fwait so that an exception goes off at the right time
202 * (as a call from the fsave or fwait in effect) rather than to
203 * the wrong process. Lazy FP saving no longer makes any sense
204 * with modern CPU's, and this simplifies a lot of things (SMP
205 * and UP become the same).
206 *
207 * NOTE! We used to use the x86 hardware context switching. The
208 * reason for not using it any more becomes apparent when you
209 * try to recover gracefully from saved state that is no longer
210 * valid (stale segment register values in particular). With the
211 * hardware task-switch, there is no way to fix up bad state in
212 * a reasonable manner.
213 *
214 * The fact that Intel documents the hardware task-switching to
215 * be slow is a fairly red herring - this code is not noticeably
216 * faster. However, there _is_ some room for improvement here,
217 * so the performance issues may eventually be a valid point.
218 * More important, however, is the fact that this allows us much
219 * more flexibility.
220 *
221 * The return value (in %ax) will be the "prev" task after
222 * the task-switch, and shows up in ret_from_fork in entry.S,
223 * for example.
224 */
225__visible __notrace_funcgraph struct task_struct *
226__switch_to(struct task_struct *prev_p, struct task_struct *next_p)
227{
228 struct thread_struct *prev = &prev_p->thread,
229 *next = &next_p->thread;
230 struct fpu *prev_fpu = &prev->fpu;
231 struct fpu *next_fpu = &next->fpu;
232 int cpu = smp_processor_id();
233 struct tss_struct *tss = &per_cpu(cpu_tss, cpu);
234
235 /* never put a printk in __switch_to... printk() calls wake_up*() indirectly */
236
237 switch_fpu_prepare(prev_fpu, cpu);
238
239 /*
240 * Save away %gs. No need to save %fs, as it was saved on the
241 * stack on entry. No need to save %es and %ds, as those are
242 * always kernel segments while inside the kernel. Doing this
243 * before setting the new TLS descriptors avoids the situation
244 * where we temporarily have non-reloadable segments in %fs
245 * and %gs. This could be an issue if the NMI handler ever
246 * used %fs or %gs (it does not today), or if the kernel is
247 * running inside of a hypervisor layer.
248 */
249 lazy_save_gs(prev->gs);
250
251 /*
252 * Load the per-thread Thread-Local Storage descriptor.
253 */
254 load_TLS(next, cpu);
255
256 /*
257 * Restore IOPL if needed. In normal use, the flags restore
258 * in the switch assembly will handle this. But if the kernel
259 * is running virtualized at a non-zero CPL, the popf will
260 * not restore flags, so it must be done in a separate step.
261 */
262 if (get_kernel_rpl() && unlikely(prev->iopl != next->iopl))
263 set_iopl_mask(next->iopl);
264
265 /*
266 * Now maybe handle debug registers and/or IO bitmaps
267 */
268 if (unlikely(task_thread_info(prev_p)->flags & _TIF_WORK_CTXSW_PREV ||
269 task_thread_info(next_p)->flags & _TIF_WORK_CTXSW_NEXT))
270 __switch_to_xtra(prev_p, next_p, tss);
271
272 /*
273 * Leave lazy mode, flushing any hypercalls made here.
274 * This must be done before restoring TLS segments so
275 * the GDT and LDT are properly updated, and must be
276 * done before fpu__restore(), so the TS bit is up
277 * to date.
278 */
279 arch_end_context_switch(next_p);
280
281 /*
282 * Reload esp0 and cpu_current_top_of_stack. This changes
283 * current_thread_info().
284 */
285 load_sp0(tss, next);
286 this_cpu_write(cpu_current_top_of_stack,
287 (unsigned long)task_stack_page(next_p) +
288 THREAD_SIZE);
289
290 /*
291 * Restore %gs if needed (which is common)
292 */
293 if (prev->gs | next->gs)
294 lazy_load_gs(next->gs);
295
296 switch_fpu_finish(next_fpu, cpu);
297
298 this_cpu_write(current_task, next_p);
299
300 /* Load the Intel cache allocation PQR MSR. */
301 intel_rdt_sched_in();
302
303 return prev_p;
304}