[PATCH v2 35/38] cxlflash: Introduce OCXL context state machine

Uma Krishnan
2018-02-26T22:24:42Z

In order to protect the OCXL hardware contexts from getting clobbered,
a simple state machine is added to indicate when a context is in open,
close or start state. The expected states are validated throughout the
code to prevent illegal operations on a context. A mutex is added to
protect writes to the context state field.

Signed-off-by: Uma Krishnan <ukrishn@linux.vnet.ibm.com>
Acked-by: Matthew R. Ochs <mrochs@linux.vnet.ibm.com>
---
drivers/scsi/cxlflash/ocxl_hw.c | 59 ++++++++++++++++++++++++++++++++++++++---
drivers/scsi/cxlflash/ocxl_hw.h | 8 ++++++
2 files changed, 64 insertions(+), 3 deletions(-)

diff --git a/drivers/scsi/cxlflash/ocxl_hw.c b/drivers/scsi/cxlflash/ocxl_hw.c
index 0e21f79..d707e4c 100644
--- a/drivers/scsi/cxlflash/ocxl_hw.c
+++ b/drivers/scsi/cxlflash/ocxl_hw.c
@@ -163,6 +163,16 @@ static struct file *ocxlflash_getfile(struct device *dev, const char *name,
static void __iomem *ocxlflash_psa_map(void *ctx_cookie)
{
struct ocxlflash_context *ctx = ctx_cookie;
+ struct device *dev = ctx->hw_afu->dev;
+
+ mutex_lock(&ctx->state_mutex);
+ if (ctx->state != STARTED) {
+ dev_err(dev, "%s: Context not started, state=%d\n", __func__,
+ ctx->state);
+ mutex_unlock(&ctx->state_mutex);
+ return NULL;
+ }
+ mutex_unlock(&ctx->state_mutex);

return ioremap(ctx->psn_phys, ctx->psn_size);
}
@@ -343,6 +353,14 @@ static int start_context(struct ocxlflash_context *ctx)
int rc = 0;
u32 pid;

+ mutex_lock(&ctx->state_mutex);
+ if (ctx->state != OPENED) {
+ dev_err(dev, "%s: Context state invalid, state=%d\n",
+ __func__, ctx->state);
+ rc = -EINVAL;
+ goto out;
+ }
+
if (master) {
ctx->psn_size = acfg->global_mmio_size;
ctx->psn_phys = afu->gmmio_phys;
@@ -366,7 +384,10 @@ static int start_context(struct ocxlflash_context *ctx)
__func__, rc);
goto out;
}
+
+ ctx->state = STARTED;
out:
+ mutex_unlock(&ctx->state_mutex);
return rc;
}

@@ -396,7 +417,15 @@ static int ocxlflash_stop_context(void *ctx_cookie)
struct ocxl_afu_config *acfg = &afu->acfg;
struct pci_dev *pdev = afu->pdev;
struct device *dev = afu->dev;
- int rc;
+ enum ocxlflash_ctx_state state;
+ int rc = 0;
+
+ mutex_lock(&ctx->state_mutex);
+ state = ctx->state;
+ ctx->state = CLOSED;
+ mutex_unlock(&ctx->state_mutex);
+ if (state != STARTED)
+ goto out;

rc = ocxl_config_terminate_pasid(pdev, acfg->dvsec_afu_control_pos,
ctx->pe);
@@ -474,7 +503,9 @@ static void *ocxlflash_dev_context_init(struct pci_dev *pdev, void *afu_cookie)

spin_lock_init(&ctx->slock);
init_waitqueue_head(&ctx->wq);
+ mutex_init(&ctx->state_mutex);

+ ctx->state = OPENED;
ctx->pe = rc;
ctx->master = false;
ctx->mapping = NULL;
@@ -499,11 +530,23 @@ static void *ocxlflash_dev_context_init(struct pci_dev *pdev, void *afu_cookie)
static int ocxlflash_release_context(void *ctx_cookie)
{
struct ocxlflash_context *ctx = ctx_cookie;
+ struct device *dev;
int rc = 0;

if (!ctx)
goto out;

+ dev = ctx->hw_afu->dev;
+ mutex_lock(&ctx->state_mutex);
+ if (ctx->state >= STARTED) {
+ dev_err(dev, "%s: Context in use, state=%d\n", __func__,
+ ctx->state);
+ mutex_unlock(&ctx->state_mutex);
+ rc = -EBUSY;
+ goto out;
+ }
+ mutex_unlock(&ctx->state_mutex);
+
idr_remove(&ctx->hw_afu->idr, ctx->pe);
ocxlflash_release_mapping(ctx);
kfree(ctx);
@@ -939,7 +982,7 @@ static unsigned int afu_poll(struct file *file, struct poll_table_struct *poll)
spin_lock_irqsave(&ctx->slock, lock_flags);
if (ctx_event_pending(ctx))
mask |= POLLIN | POLLRDNORM;
- else
+ else if (ctx->state == CLOSED)
mask |= POLLERR;
spin_unlock_irqrestore(&ctx->slock, lock_flags);

@@ -982,7 +1025,7 @@ static ssize_t afu_read(struct file *file, char __user *buf, size_t count,
for (;;) {
prepare_to_wait(&ctx->wq, &event_wait, TASK_INTERRUPTIBLE);

- if (ctx_event_pending(ctx))
+ if (ctx_event_pending(ctx) || (ctx->state == CLOSED))
break;

if (file->f_flags & O_NONBLOCK) {
@@ -1068,12 +1111,22 @@ static int ocxlflash_mmap_fault(struct vm_fault *vmf)
{
struct vm_area_struct *vma = vmf->vma;
struct ocxlflash_context *ctx = vma->vm_file->private_data;
+ struct device *dev = ctx->hw_afu->dev;
u64 mmio_area, offset;

offset = vmf->pgoff << PAGE_SHIFT;
if (offset >= ctx->psn_size)
return VM_FAULT_SIGBUS;

+ mutex_lock(&ctx->state_mutex);
+ if (ctx->state != STARTED) {
+ dev_err(dev, "%s: Context not started, state=%d\n",
+ __func__, ctx->state);
+ mutex_unlock(&ctx->state_mutex);
+ return VM_FAULT_SIGBUS;
+ }
+ mutex_unlock(&ctx->state_mutex);
+
mmio_area = ctx->psn_phys;
mmio_area += offset;

diff --git a/drivers/scsi/cxlflash/ocxl_hw.h b/drivers/scsi/cxlflash/ocxl_hw.h
index d0eac35..a4f3b90 100644
--- a/drivers/scsi/cxlflash/ocxl_hw.h
+++ b/drivers/scsi/cxlflash/ocxl_hw.h
@@ -45,6 +45,12 @@ struct ocxl_hw_afu {
int max_pasid; /* Maximum number of contexts */
};

+enum ocxlflash_ctx_state {
+ CLOSED,
+ OPENED,
+ STARTED
+};
+
struct ocxlflash_context {
struct ocxl_hw_afu *hw_afu; /* HW AFU back pointer */
struct address_space *mapping; /* Mapping for pseudo filesystem */
@@ -56,6 +62,8 @@ struct ocxlflash_context {

spinlock_t slock; /* Protects irq/fault/event updates */
wait_queue_head_t wq; /* Wait queue for poll and interrupts */
+ struct mutex state_mutex; /* Mutex to update context state */
+ enum ocxlflash_ctx_state state; /* Context state */

struct ocxlflash_irqs *irqs; /* Pointer to array of structures */
int num_irqs; /* Number of interrupts */
--
2.1.0