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x86: mp: Support APs waiting for instructions

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At present the APs (non-boot CPUs) are inited once and then parked ready
for the OS to use them. However in some cases we want to send new requests
through, such as to change MTRRs and keep them consistent across CPUs.

Change the last state of the flight plan to go into a wait loop, accepting
instructions from the main CPU.

Drop cpu_map since it is not used.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Wolfgang Wallner <wolfgang.wallner@br-automation.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
This commit is contained in:
Simon Glass
2020-07-17 08:48:16 -06:00
committed by Bin Meng
parent 8bccbc5ac0
commit c33aa3527d
4 changed files with 134 additions and 8 deletions
Download Patch File Download Diff File Expand all files Collapse all files

7
arch/x86/Kconfig
View File

@@ -603,6 +603,13 @@ config SMP
only one CPU will be enabled regardless of the number of CPUs
available.
config SMP_AP_WORK
bool
depends on SMP
help
Allow APs to do other work after initialisation instead of going
to sleep.
config MAX_CPUS
int "Maximum number of CPUs permitted"
depends on SMP

1
arch/x86/cpu/apollolake/Kconfig
View File

@@ -15,6 +15,7 @@ config INTEL_APOLLOLAKE
select TPL_PCH_SUPPORT
select PCH_SUPPORT
select P2SB
select SMP_AP_WORK
imply ENABLE_MRC_CACHE
imply AHCI_PCI
imply SCSI

123
arch/x86/cpu/mp_init.c
View File

@@ -15,6 +15,7 @@
#include <asm/atomic.h>
#include <asm/cpu.h>
#include <asm/interrupt.h>
#include <asm/io.h>
#include <asm/lapic.h>
#include <asm/microcode.h>
#include <asm/mp.h>
@@ -43,13 +44,38 @@ struct mp_flight_plan {
struct mp_flight_record *records;
};
/**
* struct mp_callback - Callback information for APs
*
* @func: Function to run
* @arg: Argument to pass to the function
* @logical_cpu_number: Either a CPU number (i.e. dev->req_seq) or a special
* value like MP_SELECT_BSP. It tells the AP whether it should process this
* callback
*/
struct mp_callback {
/**
* func() - Function to call on the AP
*
* @arg: Argument to pass
*/
void (*func)(void *arg);
void *arg;
int logical_cpu_number;
};
static struct mp_flight_plan mp_info;
struct cpu_map {
struct udevice *dev;
int apic_id;
int err_code;
};
/*
* ap_callbacks - Callback mailbox array
*
* Array of callback, one entry for each available CPU, indexed by the CPU
* number, which is dev->req_seq. The entry for the main CPU is never used.
* When this is NULL, there is no pending work for the CPU to run. When
* non-NULL it points to the mp_callback structure. This is shared between all
* CPUs, so should only be written by the main CPU.
*/
static struct mp_callback **ap_callbacks;
static inline void barrier_wait(atomic_t *b)
{
@@ -147,11 +173,12 @@ static void ap_init(unsigned int cpu_index)
debug("AP: slot %d apic_id %x, dev %s\n", cpu_index, apic_id,
dev ? dev->name : "(apic_id not found)");
/* Walk the flight plan */
/*
* Walk the flight plan, which only returns if CONFIG_SMP_AP_WORK is not
* enabled
*/
ap_do_flight_plan(dev);
/* Park the AP */
debug("parking\n");
done:
stop_this_cpu();
}
@@ -456,6 +483,81 @@ static int get_bsp(struct udevice **devp, int *cpu_countp)
return dev->req_seq >= 0 ? dev->req_seq : 0;
}
/**
* read_callback() - Read the pointer in a callback slot
*
* This is called by APs to read their callback slot to see if there is a
* pointer to new instructions
*
* @slot: Pointer to the AP's callback slot
* @return value of that pointer
*/
static struct mp_callback *read_callback(struct mp_callback **slot)
{
dmb();
return *slot;
}
/**
* store_callback() - Store a pointer to the callback slot
*
* This is called by APs to write NULL into the callback slot when they have
* finished the work requested by the BSP.
*
* @slot: Pointer to the AP's callback slot
* @val: Value to write (e.g. NULL)
*/
static void store_callback(struct mp_callback **slot, struct mp_callback *val)
{
*slot = val;
dmb();
}
/**
* ap_wait_for_instruction() - Wait for and process requests from the main CPU
*
* This is called by APs (here, everything other than the main boot CPU) to
* await instructions. They arrive in the form of a function call and argument,
* which is then called. This uses a simple mailbox with atomic read/set
*
* @cpu: CPU that is waiting
* @unused: Optional argument provided by struct mp_flight_record, not used here
* @return Does not return
*/
static int ap_wait_for_instruction(struct udevice *cpu, void *unused)
{
struct mp_callback lcb;
struct mp_callback **per_cpu_slot;
if (!IS_ENABLED(CONFIG_SMP_AP_WORK))
return 0;
per_cpu_slot = &ap_callbacks[cpu->req_seq];
while (1) {
struct mp_callback *cb = read_callback(per_cpu_slot);
if (!cb) {
asm ("pause");
continue;
}
/* Copy to local variable before using the value */
memcpy(&lcb, cb, sizeof(lcb));
mfence();
if (lcb.logical_cpu_number == MP_SELECT_ALL ||
lcb.logical_cpu_number == MP_SELECT_APS ||
cpu->req_seq == lcb.logical_cpu_number)
lcb.func(lcb.arg);
/* Indicate we are finished */
store_callback(per_cpu_slot, NULL);
}
return 0;
}
static int mp_init_cpu(struct udevice *cpu, void *unused)
{
struct cpu_platdata *plat = dev_get_parent_platdata(cpu);
@@ -468,6 +570,7 @@ static int mp_init_cpu(struct udevice *cpu, void *unused)
static struct mp_flight_record mp_steps[] = {
MP_FR_BLOCK_APS(mp_init_cpu, NULL, mp_init_cpu, NULL),
MP_FR_BLOCK_APS(ap_wait_for_instruction, NULL, NULL, NULL),
};
int mp_init(void)
@@ -505,6 +608,10 @@ int mp_init(void)
if (ret)
log_warning("Warning: Device tree does not describe all CPUs. Extra ones will not be started correctly\n");
ap_callbacks = calloc(num_cpus, sizeof(struct mp_callback *));
if (!ap_callbacks)
return -ENOMEM;
/* Copy needed parameters so that APs have a reference to the plan */
mp_info.num_records = ARRAY_SIZE(mp_steps);
mp_info.records = mp_steps;

11
arch/x86/include/asm/mp.h
View File

@@ -11,6 +11,17 @@
#include <asm/atomic.h>
#include <asm/cache.h>
enum {
/* Indicates that the function should run on all CPUs */
MP_SELECT_ALL = -1,
/* Run on boot CPUs */
MP_SELECT_BSP = -2,
/* Run on non-boot CPUs */
MP_SELECT_APS = -3,
};
typedef int (*mp_callback_t)(struct udevice *cpu, void *arg);
/*