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linux-next/drivers/xen/events/events_fifo.c
Julien Grall 22f12f0df8 xen/events: events_fifo: Don't use {get,put}_cpu() in xen_evtchn_fifo_init()
When booting Linux as Xen guest with CONFIG_DEBUG_ATOMIC, the following
splat appears:

[    0.002323] Mountpoint-cache hash table entries: 1024 (order: 1, 8192 bytes)
[    0.019717] ASID allocator initialised with 65536 entries
[    0.020019] xen:grant_table: Grant tables using version 1 layout
[    0.020051] Grant table initialized
[    0.020069] BUG: sleeping function called from invalid context at /data/src/linux/mm/page_alloc.c:4046
[    0.020100] in_atomic(): 1, irqs_disabled(): 0, pid: 1, name: swapper/0
[    0.020123] no locks held by swapper/0/1.
[    0.020143] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.13.0-rc5 #598
[    0.020166] Hardware name: FVP Base (DT)
[    0.020182] Call trace:
[    0.020199] [<ffff00000808a5c0>] dump_backtrace+0x0/0x270
[    0.020222] [<ffff00000808a95c>] show_stack+0x24/0x30
[    0.020244] [<ffff000008c1ef20>] dump_stack+0xb8/0xf0
[    0.020267] [<ffff0000081128c0>] ___might_sleep+0x1c8/0x1f8
[    0.020291] [<ffff000008112948>] __might_sleep+0x58/0x90
[    0.020313] [<ffff0000082171b8>] __alloc_pages_nodemask+0x1c0/0x12e8
[    0.020338] [<ffff00000827a110>] alloc_page_interleave+0x38/0x88
[    0.020363] [<ffff00000827a904>] alloc_pages_current+0xdc/0xf0
[    0.020387] [<ffff000008211f38>] __get_free_pages+0x28/0x50
[    0.020411] [<ffff0000086566a4>] evtchn_fifo_alloc_control_block+0x2c/0xa0
[    0.020437] [<ffff0000091747b0>] xen_evtchn_fifo_init+0x38/0xb4
[    0.020461] [<ffff0000091746c0>] xen_init_IRQ+0x44/0xc8
[    0.020484] [<ffff000009128adc>] xen_guest_init+0x250/0x300
[    0.020507] [<ffff000008083974>] do_one_initcall+0x44/0x130
[    0.020531] [<ffff000009120df8>] kernel_init_freeable+0x120/0x288
[    0.020556] [<ffff000008c31ca8>] kernel_init+0x18/0x110
[    0.020578] [<ffff000008083710>] ret_from_fork+0x10/0x40
[    0.020606] xen:events: Using FIFO-based ABI
[    0.020658] Xen: initializing cpu0
[    0.027727] Hierarchical SRCU implementation.
[    0.036235] EFI services will not be available.
[    0.043810] smp: Bringing up secondary CPUs ...

This is because get_cpu() in xen_evtchn_fifo_init() will disable
preemption, but __get_free_page() might sleep (GFP_ATOMIC is not set).

xen_evtchn_fifo_init() will always be called before SMP is initialized,
so {get,put}_cpu() could be replaced by a simple smp_processor_id().

This also avoid to modify evtchn_fifo_alloc_control_block that will be
called in other context.

Signed-off-by: Julien Grall <julien.grall@arm.com>
Reported-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Fixes: 1fe565517b ("xen/events: use the FIFO-based ABI if available")
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
2017-08-31 09:45:55 -04:00

452 lines
11 KiB
C

/*
* Xen event channels (FIFO-based ABI)
*
* Copyright (C) 2013 Citrix Systems R&D ltd.
*
* This source code is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 2 of the
* License, or (at your option) any later version.
*
* Or, when distributed separately from the Linux kernel or
* incorporated into other software packages, subject to the following
* license:
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this source file (the "Software"), to deal in the Software without
* restriction, including without limitation the rights to use, copy, modify,
* merge, publish, distribute, sublicense, and/or sell copies of the Software,
* and to permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
* IN THE SOFTWARE.
*/
#define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt
#include <linux/linkage.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/smp.h>
#include <linux/percpu.h>
#include <linux/cpu.h>
#include <asm/barrier.h>
#include <asm/sync_bitops.h>
#include <asm/xen/hypercall.h>
#include <asm/xen/hypervisor.h>
#include <xen/xen.h>
#include <xen/xen-ops.h>
#include <xen/events.h>
#include <xen/interface/xen.h>
#include <xen/interface/event_channel.h>
#include <xen/page.h>
#include "events_internal.h"
#define EVENT_WORDS_PER_PAGE (XEN_PAGE_SIZE / sizeof(event_word_t))
#define MAX_EVENT_ARRAY_PAGES (EVTCHN_FIFO_NR_CHANNELS / EVENT_WORDS_PER_PAGE)
struct evtchn_fifo_queue {
uint32_t head[EVTCHN_FIFO_MAX_QUEUES];
};
static DEFINE_PER_CPU(struct evtchn_fifo_control_block *, cpu_control_block);
static DEFINE_PER_CPU(struct evtchn_fifo_queue, cpu_queue);
static event_word_t *event_array[MAX_EVENT_ARRAY_PAGES] __read_mostly;
static unsigned event_array_pages __read_mostly;
/*
* sync_set_bit() and friends must be unsigned long aligned.
*/
#if BITS_PER_LONG > 32
#define BM(w) (unsigned long *)((unsigned long)w & ~0x7UL)
#define EVTCHN_FIFO_BIT(b, w) \
(((unsigned long)w & 0x4UL) ? (EVTCHN_FIFO_ ##b + 32) : EVTCHN_FIFO_ ##b)
#else
#define BM(w) ((unsigned long *)(w))
#define EVTCHN_FIFO_BIT(b, w) EVTCHN_FIFO_ ##b
#endif
static inline event_word_t *event_word_from_port(unsigned port)
{
unsigned i = port / EVENT_WORDS_PER_PAGE;
return event_array[i] + port % EVENT_WORDS_PER_PAGE;
}
static unsigned evtchn_fifo_max_channels(void)
{
return EVTCHN_FIFO_NR_CHANNELS;
}
static unsigned evtchn_fifo_nr_channels(void)
{
return event_array_pages * EVENT_WORDS_PER_PAGE;
}
static int init_control_block(int cpu,
struct evtchn_fifo_control_block *control_block)
{
struct evtchn_fifo_queue *q = &per_cpu(cpu_queue, cpu);
struct evtchn_init_control init_control;
unsigned int i;
/* Reset the control block and the local HEADs. */
clear_page(control_block);
for (i = 0; i < EVTCHN_FIFO_MAX_QUEUES; i++)
q->head[i] = 0;
init_control.control_gfn = virt_to_gfn(control_block);
init_control.offset = 0;
init_control.vcpu = xen_vcpu_nr(cpu);
return HYPERVISOR_event_channel_op(EVTCHNOP_init_control, &init_control);
}
static void free_unused_array_pages(void)
{
unsigned i;
for (i = event_array_pages; i < MAX_EVENT_ARRAY_PAGES; i++) {
if (!event_array[i])
break;
free_page((unsigned long)event_array[i]);
event_array[i] = NULL;
}
}
static void init_array_page(event_word_t *array_page)
{
unsigned i;
for (i = 0; i < EVENT_WORDS_PER_PAGE; i++)
array_page[i] = 1 << EVTCHN_FIFO_MASKED;
}
static int evtchn_fifo_setup(struct irq_info *info)
{
unsigned port = info->evtchn;
unsigned new_array_pages;
int ret;
new_array_pages = port / EVENT_WORDS_PER_PAGE + 1;
if (new_array_pages > MAX_EVENT_ARRAY_PAGES)
return -EINVAL;
while (event_array_pages < new_array_pages) {
void *array_page;
struct evtchn_expand_array expand_array;
/* Might already have a page if we've resumed. */
array_page = event_array[event_array_pages];
if (!array_page) {
array_page = (void *)__get_free_page(GFP_KERNEL);
if (array_page == NULL) {
ret = -ENOMEM;
goto error;
}
event_array[event_array_pages] = array_page;
}
/* Mask all events in this page before adding it. */
init_array_page(array_page);
expand_array.array_gfn = virt_to_gfn(array_page);
ret = HYPERVISOR_event_channel_op(EVTCHNOP_expand_array, &expand_array);
if (ret < 0)
goto error;
event_array_pages++;
}
return 0;
error:
if (event_array_pages == 0)
panic("xen: unable to expand event array with initial page (%d)\n", ret);
else
pr_err("unable to expand event array (%d)\n", ret);
free_unused_array_pages();
return ret;
}
static void evtchn_fifo_bind_to_cpu(struct irq_info *info, unsigned cpu)
{
/* no-op */
}
static void evtchn_fifo_clear_pending(unsigned port)
{
event_word_t *word = event_word_from_port(port);
sync_clear_bit(EVTCHN_FIFO_BIT(PENDING, word), BM(word));
}
static void evtchn_fifo_set_pending(unsigned port)
{
event_word_t *word = event_word_from_port(port);
sync_set_bit(EVTCHN_FIFO_BIT(PENDING, word), BM(word));
}
static bool evtchn_fifo_is_pending(unsigned port)
{
event_word_t *word = event_word_from_port(port);
return sync_test_bit(EVTCHN_FIFO_BIT(PENDING, word), BM(word));
}
static bool evtchn_fifo_test_and_set_mask(unsigned port)
{
event_word_t *word = event_word_from_port(port);
return sync_test_and_set_bit(EVTCHN_FIFO_BIT(MASKED, word), BM(word));
}
static void evtchn_fifo_mask(unsigned port)
{
event_word_t *word = event_word_from_port(port);
sync_set_bit(EVTCHN_FIFO_BIT(MASKED, word), BM(word));
}
static bool evtchn_fifo_is_masked(unsigned port)
{
event_word_t *word = event_word_from_port(port);
return sync_test_bit(EVTCHN_FIFO_BIT(MASKED, word), BM(word));
}
/*
* Clear MASKED, spinning if BUSY is set.
*/
static void clear_masked(volatile event_word_t *word)
{
event_word_t new, old, w;
w = *word;
do {
old = w & ~(1 << EVTCHN_FIFO_BUSY);
new = old & ~(1 << EVTCHN_FIFO_MASKED);
w = sync_cmpxchg(word, old, new);
} while (w != old);
}
static void evtchn_fifo_unmask(unsigned port)
{
event_word_t *word = event_word_from_port(port);
BUG_ON(!irqs_disabled());
clear_masked(word);
if (evtchn_fifo_is_pending(port)) {
struct evtchn_unmask unmask = { .port = port };
(void)HYPERVISOR_event_channel_op(EVTCHNOP_unmask, &unmask);
}
}
static uint32_t clear_linked(volatile event_word_t *word)
{
event_word_t new, old, w;
w = *word;
do {
old = w;
new = (w & ~((1 << EVTCHN_FIFO_LINKED)
| EVTCHN_FIFO_LINK_MASK));
} while ((w = sync_cmpxchg(word, old, new)) != old);
return w & EVTCHN_FIFO_LINK_MASK;
}
static void handle_irq_for_port(unsigned port)
{
int irq;
irq = get_evtchn_to_irq(port);
if (irq != -1)
generic_handle_irq(irq);
}
static void consume_one_event(unsigned cpu,
struct evtchn_fifo_control_block *control_block,
unsigned priority, unsigned long *ready,
bool drop)
{
struct evtchn_fifo_queue *q = &per_cpu(cpu_queue, cpu);
uint32_t head;
unsigned port;
event_word_t *word;
head = q->head[priority];
/*
* Reached the tail last time? Read the new HEAD from the
* control block.
*/
if (head == 0) {
virt_rmb(); /* Ensure word is up-to-date before reading head. */
head = control_block->head[priority];
}
port = head;
word = event_word_from_port(port);
head = clear_linked(word);
/*
* If the link is non-zero, there are more events in the
* queue, otherwise the queue is empty.
*
* If the queue is empty, clear this priority from our local
* copy of the ready word.
*/
if (head == 0)
clear_bit(priority, ready);
if (evtchn_fifo_is_pending(port) && !evtchn_fifo_is_masked(port)) {
if (unlikely(drop))
pr_warn("Dropping pending event for port %u\n", port);
else
handle_irq_for_port(port);
}
q->head[priority] = head;
}
static void __evtchn_fifo_handle_events(unsigned cpu, bool drop)
{
struct evtchn_fifo_control_block *control_block;
unsigned long ready;
unsigned q;
control_block = per_cpu(cpu_control_block, cpu);
ready = xchg(&control_block->ready, 0);
while (ready) {
q = find_first_bit(&ready, EVTCHN_FIFO_MAX_QUEUES);
consume_one_event(cpu, control_block, q, &ready, drop);
ready |= xchg(&control_block->ready, 0);
}
}
static void evtchn_fifo_handle_events(unsigned cpu)
{
__evtchn_fifo_handle_events(cpu, false);
}
static void evtchn_fifo_resume(void)
{
unsigned cpu;
for_each_possible_cpu(cpu) {
void *control_block = per_cpu(cpu_control_block, cpu);
int ret;
if (!control_block)
continue;
/*
* If this CPU is offline, take the opportunity to
* free the control block while it is not being
* used.
*/
if (!cpu_online(cpu)) {
free_page((unsigned long)control_block);
per_cpu(cpu_control_block, cpu) = NULL;
continue;
}
ret = init_control_block(cpu, control_block);
BUG_ON(ret < 0);
}
/*
* The event array starts out as empty again and is extended
* as normal when events are bound. The existing pages will
* be reused.
*/
event_array_pages = 0;
}
static const struct evtchn_ops evtchn_ops_fifo = {
.max_channels = evtchn_fifo_max_channels,
.nr_channels = evtchn_fifo_nr_channels,
.setup = evtchn_fifo_setup,
.bind_to_cpu = evtchn_fifo_bind_to_cpu,
.clear_pending = evtchn_fifo_clear_pending,
.set_pending = evtchn_fifo_set_pending,
.is_pending = evtchn_fifo_is_pending,
.test_and_set_mask = evtchn_fifo_test_and_set_mask,
.mask = evtchn_fifo_mask,
.unmask = evtchn_fifo_unmask,
.handle_events = evtchn_fifo_handle_events,
.resume = evtchn_fifo_resume,
};
static int evtchn_fifo_alloc_control_block(unsigned cpu)
{
void *control_block = NULL;
int ret = -ENOMEM;
control_block = (void *)__get_free_page(GFP_KERNEL);
if (control_block == NULL)
goto error;
ret = init_control_block(cpu, control_block);
if (ret < 0)
goto error;
per_cpu(cpu_control_block, cpu) = control_block;
return 0;
error:
free_page((unsigned long)control_block);
return ret;
}
static int xen_evtchn_cpu_prepare(unsigned int cpu)
{
if (!per_cpu(cpu_control_block, cpu))
return evtchn_fifo_alloc_control_block(cpu);
return 0;
}
static int xen_evtchn_cpu_dead(unsigned int cpu)
{
__evtchn_fifo_handle_events(cpu, true);
return 0;
}
int __init xen_evtchn_fifo_init(void)
{
int cpu = smp_processor_id();
int ret;
ret = evtchn_fifo_alloc_control_block(cpu);
if (ret < 0)
return ret;
pr_info("Using FIFO-based ABI\n");
evtchn_ops = &evtchn_ops_fifo;
cpuhp_setup_state_nocalls(CPUHP_XEN_EVTCHN_PREPARE,
"xen/evtchn:prepare",
xen_evtchn_cpu_prepare, xen_evtchn_cpu_dead);
return ret;
}