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linux/drivers/misc/cxl/sysfs.c
Ian Munsie ee41d11d53 cxl: Change contexts_lock to a mutex to fix sleep while atomic bug 
We had a known sleep while atomic bug if a CXL device was forcefully
unbound while it was in use. This could occur as a result of EEH, or
manually induced with something like this while the device was in use:

echo 0000:01:00.0 > /sys/bus/pci/drivers/cxl-pci/unbind

The issue was that in this code path we iterated over each context and
forcefully detached it with the contexts_lock spin lock held, however
the detach also needed to take the spu_mutex, and call schedule.

This patch changes the contexts_lock to a mutex so that we are not in
atomic context while doing the detach, thereby avoiding the sleep while
atomic.

Also delete the related TODO comment, which suggested an alternate
solution which turned out to not be workable.

Cc: stable@vger.kernel.org
Signed-off-by: Ian Munsie <imunsie@au1.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
2014-12-12 13:06:47 +11:00

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/*
* Copyright 2014 IBM Corp.
*
* This program 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.
*/
#include <linux/kernel.h>
#include <linux/device.h>
#include <linux/sysfs.h>
#include "cxl.h"
#define to_afu_chardev_m(d) dev_get_drvdata(d)
/********* Adapter attributes **********************************************/
static ssize_t caia_version_show(struct device *device,
struct device_attribute *attr,
char *buf)
{
struct cxl *adapter = to_cxl_adapter(device);
return scnprintf(buf, PAGE_SIZE, "%i.%i\n", adapter->caia_major,
adapter->caia_minor);
}
static ssize_t psl_revision_show(struct device *device,
struct device_attribute *attr,
char *buf)
{
struct cxl *adapter = to_cxl_adapter(device);
return scnprintf(buf, PAGE_SIZE, "%i\n", adapter->psl_rev);
}
static ssize_t base_image_show(struct device *device,
struct device_attribute *attr,
char *buf)
{
struct cxl *adapter = to_cxl_adapter(device);
return scnprintf(buf, PAGE_SIZE, "%i\n", adapter->base_image);
}
static ssize_t image_loaded_show(struct device *device,
struct device_attribute *attr,
char *buf)
{
struct cxl *adapter = to_cxl_adapter(device);
if (adapter->user_image_loaded)
return scnprintf(buf, PAGE_SIZE, "user\n");
return scnprintf(buf, PAGE_SIZE, "factory\n");
}
static struct device_attribute adapter_attrs[] = {
__ATTR_RO(caia_version),
__ATTR_RO(psl_revision),
__ATTR_RO(base_image),
__ATTR_RO(image_loaded),
};
/********* AFU master specific attributes **********************************/
static ssize_t mmio_size_show_master(struct device *device,
struct device_attribute *attr,
char *buf)
{
struct cxl_afu *afu = to_afu_chardev_m(device);
return scnprintf(buf, PAGE_SIZE, "%llu\n", afu->adapter->ps_size);
}
static ssize_t pp_mmio_off_show(struct device *device,
struct device_attribute *attr,
char *buf)
{
struct cxl_afu *afu = to_afu_chardev_m(device);
return scnprintf(buf, PAGE_SIZE, "%llu\n", afu->pp_offset);
}
static ssize_t pp_mmio_len_show(struct device *device,
struct device_attribute *attr,
char *buf)
{
struct cxl_afu *afu = to_afu_chardev_m(device);
return scnprintf(buf, PAGE_SIZE, "%llu\n", afu->pp_size);
}
static struct device_attribute afu_master_attrs[] = {
__ATTR(mmio_size, S_IRUGO, mmio_size_show_master, NULL),
__ATTR_RO(pp_mmio_off),
__ATTR_RO(pp_mmio_len),
};
/********* AFU attributes **************************************************/
static ssize_t mmio_size_show(struct device *device,
struct device_attribute *attr,
char *buf)
{
struct cxl_afu *afu = to_cxl_afu(device);
if (afu->pp_size)
return scnprintf(buf, PAGE_SIZE, "%llu\n", afu->pp_size);
return scnprintf(buf, PAGE_SIZE, "%llu\n", afu->adapter->ps_size);
}
static ssize_t reset_store_afu(struct device *device,
struct device_attribute *attr,
const char *buf, size_t count)
{
struct cxl_afu *afu = to_cxl_afu(device);
int rc;
/* Not safe to reset if it is currently in use */
mutex_lock(&afu->contexts_lock);
if (!idr_is_empty(&afu->contexts_idr)) {
rc = -EBUSY;
goto err;
}
if ((rc = cxl_afu_reset(afu)))
goto err;
rc = count;
err:
mutex_unlock(&afu->contexts_lock);
return rc;
}
static ssize_t irqs_min_show(struct device *device,
struct device_attribute *attr,
char *buf)
{
struct cxl_afu *afu = to_cxl_afu(device);
return scnprintf(buf, PAGE_SIZE, "%i\n", afu->pp_irqs);
}
static ssize_t irqs_max_show(struct device *device,
struct device_attribute *attr,
char *buf)
{
struct cxl_afu *afu = to_cxl_afu(device);
return scnprintf(buf, PAGE_SIZE, "%i\n", afu->irqs_max);
}
static ssize_t irqs_max_store(struct device *device,
struct device_attribute *attr,
const char *buf, size_t count)
{
struct cxl_afu *afu = to_cxl_afu(device);
ssize_t ret;
int irqs_max;
ret = sscanf(buf, "%i", &irqs_max);
if (ret != 1)
return -EINVAL;
if (irqs_max < afu->pp_irqs)
return -EINVAL;
if (irqs_max > afu->adapter->user_irqs)
return -EINVAL;
afu->irqs_max = irqs_max;
return count;
}
static ssize_t modes_supported_show(struct device *device,
struct device_attribute *attr, char *buf)
{
struct cxl_afu *afu = to_cxl_afu(device);
char *p = buf, *end = buf + PAGE_SIZE;
if (afu->modes_supported & CXL_MODE_DEDICATED)
p += scnprintf(p, end - p, "dedicated_process\n");
if (afu->modes_supported & CXL_MODE_DIRECTED)
p += scnprintf(p, end - p, "afu_directed\n");
return (p - buf);
}
static ssize_t prefault_mode_show(struct device *device,
struct device_attribute *attr,
char *buf)
{
struct cxl_afu *afu = to_cxl_afu(device);
switch (afu->prefault_mode) {
case CXL_PREFAULT_WED:
return scnprintf(buf, PAGE_SIZE, "work_element_descriptor\n");
case CXL_PREFAULT_ALL:
return scnprintf(buf, PAGE_SIZE, "all\n");
default:
return scnprintf(buf, PAGE_SIZE, "none\n");
}
}
static ssize_t prefault_mode_store(struct device *device,
struct device_attribute *attr,
const char *buf, size_t count)
{
struct cxl_afu *afu = to_cxl_afu(device);
enum prefault_modes mode = -1;
if (!strncmp(buf, "work_element_descriptor", 23))
mode = CXL_PREFAULT_WED;
if (!strncmp(buf, "all", 3))
mode = CXL_PREFAULT_ALL;
if (!strncmp(buf, "none", 4))
mode = CXL_PREFAULT_NONE;
if (mode == -1)
return -EINVAL;
afu->prefault_mode = mode;
return count;
}
static ssize_t mode_show(struct device *device,
struct device_attribute *attr,
char *buf)
{
struct cxl_afu *afu = to_cxl_afu(device);
if (afu->current_mode == CXL_MODE_DEDICATED)
return scnprintf(buf, PAGE_SIZE, "dedicated_process\n");
if (afu->current_mode == CXL_MODE_DIRECTED)
return scnprintf(buf, PAGE_SIZE, "afu_directed\n");
return scnprintf(buf, PAGE_SIZE, "none\n");
}
static ssize_t mode_store(struct device *device, struct device_attribute *attr,
const char *buf, size_t count)
{
struct cxl_afu *afu = to_cxl_afu(device);
int old_mode, mode = -1;
int rc = -EBUSY;
/* can't change this if we have a user */
mutex_lock(&afu->contexts_lock);
if (!idr_is_empty(&afu->contexts_idr))
goto err;
if (!strncmp(buf, "dedicated_process", 17))
mode = CXL_MODE_DEDICATED;
if (!strncmp(buf, "afu_directed", 12))
mode = CXL_MODE_DIRECTED;
if (!strncmp(buf, "none", 4))
mode = 0;
if (mode == -1) {
rc = -EINVAL;
goto err;
}
/*
* cxl_afu_deactivate_mode needs to be done outside the lock, prevent
* other contexts coming in before we are ready:
*/
old_mode = afu->current_mode;
afu->current_mode = 0;
afu->num_procs = 0;
mutex_unlock(&afu->contexts_lock);
if ((rc = _cxl_afu_deactivate_mode(afu, old_mode)))
return rc;
if ((rc = cxl_afu_activate_mode(afu, mode)))
return rc;
return count;
err:
mutex_unlock(&afu->contexts_lock);
return rc;
}
static ssize_t api_version_show(struct device *device,
struct device_attribute *attr,
char *buf)
{
return scnprintf(buf, PAGE_SIZE, "%i\n", CXL_API_VERSION);
}
static ssize_t api_version_compatible_show(struct device *device,
struct device_attribute *attr,
char *buf)
{
return scnprintf(buf, PAGE_SIZE, "%i\n", CXL_API_VERSION_COMPATIBLE);
}
static struct device_attribute afu_attrs[] = {
__ATTR_RO(mmio_size),
__ATTR_RO(irqs_min),
__ATTR_RW(irqs_max),
__ATTR_RO(modes_supported),
__ATTR_RW(mode),
__ATTR_RW(prefault_mode),
__ATTR_RO(api_version),
__ATTR_RO(api_version_compatible),
__ATTR(reset, S_IWUSR, NULL, reset_store_afu),
};
int cxl_sysfs_adapter_add(struct cxl *adapter)
{
int i, rc;
for (i = 0; i < ARRAY_SIZE(adapter_attrs); i++) {
if ((rc = device_create_file(&adapter->dev, &adapter_attrs[i])))
goto err;
}
return 0;
err:
for (i--; i >= 0; i--)
device_remove_file(&adapter->dev, &adapter_attrs[i]);
return rc;
}
void cxl_sysfs_adapter_remove(struct cxl *adapter)
{
int i;
for (i = 0; i < ARRAY_SIZE(adapter_attrs); i++)
device_remove_file(&adapter->dev, &adapter_attrs[i]);
}
int cxl_sysfs_afu_add(struct cxl_afu *afu)
{
int i, rc;
for (i = 0; i < ARRAY_SIZE(afu_attrs); i++) {
if ((rc = device_create_file(&afu->dev, &afu_attrs[i])))
goto err;
}
return 0;
err:
for (i--; i >= 0; i--)
device_remove_file(&afu->dev, &afu_attrs[i]);
return rc;
}
void cxl_sysfs_afu_remove(struct cxl_afu *afu)
{
int i;
for (i = 0; i < ARRAY_SIZE(afu_attrs); i++)
device_remove_file(&afu->dev, &afu_attrs[i]);
}
int cxl_sysfs_afu_m_add(struct cxl_afu *afu)
{
int i, rc;
for (i = 0; i < ARRAY_SIZE(afu_master_attrs); i++) {
if ((rc = device_create_file(afu->chardev_m, &afu_master_attrs[i])))
goto err;
}
return 0;
err:
for (i--; i >= 0; i--)
device_remove_file(afu->chardev_m, &afu_master_attrs[i]);
return rc;
}
void cxl_sysfs_afu_m_remove(struct cxl_afu *afu)
{
int i;
for (i = 0; i < ARRAY_SIZE(afu_master_attrs); i++)
device_remove_file(afu->chardev_m, &afu_master_attrs[i]);
}
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