Commit adc9b2df authored by James Morse's avatar James Morse Committed by Will Deacon

arm64: kernel: Rework finisher callback out of __cpu_suspend_enter()

Hibernate could make use of the cpu_suspend() code to save/restore cpu
state, however it needs to be able to return '0' from the 'finisher'.

Rework cpu_suspend() so that the finisher is called from C code,
independently from the save/restore of cpu state. Space to save the context
in is allocated in the caller's stack frame, and passed into
__cpu_suspend_enter().

Hibernate's use of this API will look like a copy of the cpu_suspend()
function.
Signed-off-by: default avatarJames Morse <james.morse@arm.com>
Acked-by: default avatarLorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
parent 67f69197
......@@ -2,6 +2,7 @@
#define __ASM_SUSPEND_H
#define NR_CTX_REGS 11
#define NR_CALLEE_SAVED_REGS 12
/*
* struct cpu_suspend_ctx must be 16-byte aligned since it is allocated on
......@@ -21,6 +22,25 @@ struct sleep_save_sp {
phys_addr_t save_ptr_stash_phys;
};
/*
* Memory to save the cpu state is allocated on the stack by
* __cpu_suspend_enter()'s caller, and populated by __cpu_suspend_enter().
* This data must survive until cpu_resume() is called.
*
* This struct desribes the size and the layout of the saved cpu state.
* The layout of the callee_saved_regs is defined by the implementation
* of __cpu_suspend_enter(), and cpu_resume(). This struct must be passed
* in by the caller as __cpu_suspend_enter()'s stack-frame is gone once it
* returns, and the data would be subsequently corrupted by the call to the
* finisher.
*/
struct sleep_stack_data {
struct cpu_suspend_ctx system_regs;
unsigned long callee_saved_regs[NR_CALLEE_SAVED_REGS];
};
extern int cpu_suspend(unsigned long arg, int (*fn)(unsigned long));
extern void cpu_resume(void);
int __cpu_suspend_enter(struct sleep_stack_data *state);
void __cpu_suspend_exit(void);
#endif
......@@ -122,6 +122,8 @@ int main(void)
DEFINE(SLEEP_SAVE_SP_SZ, sizeof(struct sleep_save_sp));
DEFINE(SLEEP_SAVE_SP_PHYS, offsetof(struct sleep_save_sp, save_ptr_stash_phys));
DEFINE(SLEEP_SAVE_SP_VIRT, offsetof(struct sleep_save_sp, save_ptr_stash));
DEFINE(SLEEP_STACK_DATA_SYSTEM_REGS, offsetof(struct sleep_stack_data, system_regs));
DEFINE(SLEEP_STACK_DATA_CALLEE_REGS, offsetof(struct sleep_stack_data, callee_saved_regs));
#endif
DEFINE(ARM_SMCCC_RES_X0_OFFS, offsetof(struct arm_smccc_res, a0));
DEFINE(ARM_SMCCC_RES_X2_OFFS, offsetof(struct arm_smccc_res, a2));
......
......@@ -49,37 +49,30 @@
orr \dst, \dst, \mask // dst|=(aff3>>rs3)
.endm
/*
* Save CPU state for a suspend and execute the suspend finisher.
* On success it will return 0 through cpu_resume - ie through a CPU
* soft/hard reboot from the reset vector.
* On failure it returns the suspend finisher return value or force
* -EOPNOTSUPP if the finisher erroneously returns 0 (the suspend finisher
* is not allowed to return, if it does this must be considered failure).
* It saves callee registers, and allocates space on the kernel stack
* to save the CPU specific registers + some other data for resume.
* Save CPU state in the provided sleep_stack_data area, and publish its
* location for cpu_resume()'s use in sleep_save_stash.
*
* x0 = suspend finisher argument
* x1 = suspend finisher function pointer
* cpu_resume() will restore this saved state, and return. Because the
* link-register is saved and restored, it will appear to return from this
* function. So that the caller can tell the suspend/resume paths apart,
* __cpu_suspend_enter() will always return a non-zero value, whereas the
* path through cpu_resume() will return 0.
*
* x0 = struct sleep_stack_data area
*/
ENTRY(__cpu_suspend_enter)
stp x29, lr, [sp, #-96]!
stp x19, x20, [sp,#16]
stp x21, x22, [sp,#32]
stp x23, x24, [sp,#48]
stp x25, x26, [sp,#64]
stp x27, x28, [sp,#80]
/*
* Stash suspend finisher and its argument in x20 and x19
*/
mov x19, x0
mov x20, x1
stp x29, lr, [x0, #SLEEP_STACK_DATA_CALLEE_REGS]
stp x19, x20, [x0,#SLEEP_STACK_DATA_CALLEE_REGS+16]
stp x21, x22, [x0,#SLEEP_STACK_DATA_CALLEE_REGS+32]
stp x23, x24, [x0,#SLEEP_STACK_DATA_CALLEE_REGS+48]
stp x25, x26, [x0,#SLEEP_STACK_DATA_CALLEE_REGS+64]
stp x27, x28, [x0,#SLEEP_STACK_DATA_CALLEE_REGS+80]
/* save the sp in cpu_suspend_ctx */
mov x2, sp
sub sp, sp, #CPU_SUSPEND_SZ // allocate cpu_suspend_ctx
mov x0, sp
/*
* x0 now points to struct cpu_suspend_ctx allocated on the stack
*/
str x2, [x0, #CPU_CTX_SP]
str x2, [x0, #SLEEP_STACK_DATA_SYSTEM_REGS + CPU_CTX_SP]
/* find the mpidr_hash */
ldr x1, =sleep_save_sp
ldr x1, [x1, #SLEEP_SAVE_SP_VIRT]
mrs x7, mpidr_el1
......@@ -93,34 +86,11 @@ ENTRY(__cpu_suspend_enter)
ldp w5, w6, [x9, #(MPIDR_HASH_SHIFTS + 8)]
compute_mpidr_hash x8, x3, x4, x5, x6, x7, x10
add x1, x1, x8, lsl #3
stp x29, lr, [sp, #-16]!
bl __cpu_suspend_save
/*
* Grab suspend finisher in x20 and its argument in x19
*/
mov x0, x19
mov x1, x20
/*
* We are ready for power down, fire off the suspend finisher
* in x1, with argument in x0
*/
blr x1
/*
* Never gets here, unless suspend finisher fails.
* Successful cpu_suspend should return from cpu_resume, returning
* through this code path is considered an error
* If the return value is set to 0 force x0 = -EOPNOTSUPP
* to make sure a proper error condition is propagated
*/
cmp x0, #0
mov x3, #-EOPNOTSUPP
csel x0, x3, x0, eq
add sp, sp, #CPU_SUSPEND_SZ // rewind stack pointer
ldp x19, x20, [sp, #16]
ldp x21, x22, [sp, #32]
ldp x23, x24, [sp, #48]
ldp x25, x26, [sp, #64]
ldp x27, x28, [sp, #80]
ldp x29, lr, [sp], #96
ldp x29, lr, [sp], #16
mov x0, #1
ret
ENDPROC(__cpu_suspend_enter)
.ltorg
......@@ -150,12 +120,6 @@ cpu_resume_after_mmu:
bl kasan_unpoison_remaining_stack
#endif
mov x0, #0 // return zero on success
ldp x19, x20, [sp, #16]
ldp x21, x22, [sp, #32]
ldp x23, x24, [sp, #48]
ldp x25, x26, [sp, #64]
ldp x27, x28, [sp, #80]
ldp x29, lr, [sp], #96
ret
ENDPROC(cpu_resume_after_mmu)
......@@ -172,6 +136,8 @@ ENTRY(cpu_resume)
/* x7 contains hash index, let's use it to grab context pointer */
ldr_l x0, sleep_save_sp + SLEEP_SAVE_SP_PHYS
ldr x0, [x0, x7, lsl #3]
add x29, x0, #SLEEP_STACK_DATA_CALLEE_REGS
add x0, x0, #SLEEP_STACK_DATA_SYSTEM_REGS
/* load sp from context */
ldr x2, [x0, #CPU_CTX_SP]
/* load physical address of identity map page table in x1 */
......@@ -185,5 +151,12 @@ ENTRY(cpu_resume)
* pointer and x1 to contain physical address of 1:1 page tables
*/
bl cpu_do_resume // PC relative jump, MMU off
/* Can't access these by physical address once the MMU is on */
ldp x19, x20, [x29, #16]
ldp x21, x22, [x29, #32]
ldp x23, x24, [x29, #48]
ldp x25, x26, [x29, #64]
ldp x27, x28, [x29, #80]
ldp x29, lr, [x29]
b cpu_resume_mmu // Resume MMU, never returns
ENDPROC(cpu_resume)
......@@ -10,22 +10,22 @@
#include <asm/suspend.h>
#include <asm/tlbflush.h>
extern int __cpu_suspend_enter(unsigned long arg, int (*fn)(unsigned long));
/*
* This is called by __cpu_suspend_enter() to save the state, and do whatever
* flushing is required to ensure that when the CPU goes to sleep we have
* the necessary data available when the caches are not searched.
*
* ptr: CPU context virtual address
* ptr: sleep_stack_data containing cpu state virtual address.
* save_ptr: address of the location where the context physical address
* must be saved
*/
void notrace __cpu_suspend_save(struct cpu_suspend_ctx *ptr,
void notrace __cpu_suspend_save(struct sleep_stack_data *ptr,
phys_addr_t *save_ptr)
{
*save_ptr = virt_to_phys(ptr);
cpu_do_suspend(ptr);
cpu_do_suspend(&ptr->system_regs);
/*
* Only flush the context that must be retrieved with the MMU
* off. VA primitives ensure the flush is applied to all
......@@ -51,6 +51,30 @@ void __init cpu_suspend_set_dbg_restorer(void (*hw_bp_restore)(void *))
hw_breakpoint_restore = hw_bp_restore;
}
void notrace __cpu_suspend_exit(void)
{
/*
* We are resuming from reset with the idmap active in TTBR0_EL1.
* We must uninstall the idmap and restore the expected MMU
* state before we can possibly return to userspace.
*/
cpu_uninstall_idmap();
/*
* Restore per-cpu offset before any kernel
* subsystem relying on it has a chance to run.
*/
set_my_cpu_offset(per_cpu_offset(smp_processor_id()));
/*
* Restore HW breakpoint registers to sane values
* before debug exceptions are possibly reenabled
* through local_dbg_restore.
*/
if (hw_breakpoint_restore)
hw_breakpoint_restore(NULL);
}
/*
* cpu_suspend
*
......@@ -60,8 +84,9 @@ void __init cpu_suspend_set_dbg_restorer(void (*hw_bp_restore)(void *))
*/
int cpu_suspend(unsigned long arg, int (*fn)(unsigned long))
{
int ret;
int ret = 0;
unsigned long flags;
struct sleep_stack_data state;
/*
* From this point debug exceptions are disabled to prevent
......@@ -77,34 +102,21 @@ int cpu_suspend(unsigned long arg, int (*fn)(unsigned long))
*/
pause_graph_tracing();
/*
* mm context saved on the stack, it will be restored when
* the cpu comes out of reset through the identity mapped
* page tables, so that the thread address space is properly
* set-up on function return.
*/
ret = __cpu_suspend_enter(arg, fn);
if (ret == 0) {
/*
* We are resuming from reset with the idmap active in TTBR0_EL1.
* We must uninstall the idmap and restore the expected MMU
* state before we can possibly return to userspace.
*/
cpu_uninstall_idmap();
/*
* Restore per-cpu offset before any kernel
* subsystem relying on it has a chance to run.
*/
set_my_cpu_offset(per_cpu_offset(smp_processor_id()));
if (__cpu_suspend_enter(&state)) {
/* Call the suspend finisher */
ret = fn(arg);
/*
* Restore HW breakpoint registers to sane values
* before debug exceptions are possibly reenabled
* through local_dbg_restore.
* Never gets here, unless the suspend finisher fails.
* Successful cpu_suspend() should return from cpu_resume(),
* returning through this code path is considered an error
* If the return value is set to 0 force ret = -EOPNOTSUPP
* to make sure a proper error condition is propagated
*/
if (hw_breakpoint_restore)
hw_breakpoint_restore(NULL);
if (!ret)
ret = -EOPNOTSUPP;
} else {
__cpu_suspend_exit();
}
unpause_graph_tracing();
......
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