[PATCH v2 1/2] cxlflash: Fix regression issue with re-ordering patch
Uma Krishnan
ukrishn at linux.vnet.ibm.com
Sat Mar 26 06:26:34 AEDT 2016
From: "Manoj N. Kumar" <manoj at linux.vnet.ibm.com>
While running 'sg_reset -H' back to back the following exception was seen:
[ 735.115695] Faulting instruction address: 0xd0000000098c0864
cpu 0x0: Vector: 300 (Data Access) at [c000000ffffafa80]
pc: d0000000098c0864: cxlflash_async_err_irq+0x84/0x5c0 [cxlflash]
lr: c00000000013aed0: handle_irq_event_percpu+0xa0/0x310
sp: c000000ffffafd00
msr: 9000000000009033
dar: 2010000
dsisr: 40000000
current = 0xc000000001510880
paca = 0xc00000000fb80000 softe: 0 irq_happened: 0x01
pid = 0, comm = swapper/0
Linux version 4.5.0-491-26f710d+
enter ? for help
[c000000ffffafe10] c00000000013aed0 handle_irq_event_percpu+0xa0/0x310
[c000000ffffafed0] c00000000013b1a8 handle_irq_event+0x68/0xc0
[c000000ffffaff00] c0000000001404ec handle_fasteoi_irq+0xec/0x2a0
[c000000ffffaff30] c00000000013a084 generic_handle_irq+0x54/0x80
[c000000ffffaff60] c000000000011130 __do_irq+0x80/0x1d0
[c000000ffffaff90] c000000000024d40 call_do_irq+0x14/0x24
[c000000001573a20] c000000000011318 do_IRQ+0x98/0x140
[c000000001573a70] c000000000002594 hardware_interrupt_common+0x114/0x180
This exception is being hit because the async_err interrupt path performs
an MMIO to read the interrupt status register. The MMIO region in this
case is not available.
Commit 6ded8b3cbd9a ("cxlflash: Unmap problem state area before detaching
master context") re-ordered the sequence in which term_mc() and stop_afu()
are called. This introduces a window for interrupts to come in with the
problem space area unmapped, that did not exist previously.
The fix is to separate the disabling of all AFU interrupts to a distinct
function, term_intr() so that it is the first thing that is done in the
tear down process.
To keep the initialization process symmetric, separate the AFU interrupt
setup also to a distinct function: init_intr().
Fixes: 6ded8b3cbd9a ("cxlflash: Unmap problem state area before detaching master context")
Signed-off-by: Manoj N. Kumar <manoj at linux.vnet.ibm.com>
Acked-by: Matthew R. Ochs <mrochs at linux.vnet.ibm.com>
Reviewed-by: Johannes Thumshirn <jthumshirn at suse.de>
Signed-off-by: Uma Krishnan <ukrishn at linux.vnet.ibm.com>
---
drivers/scsi/cxlflash/main.c | 130 ++++++++++++++++++++++++++++++-------------
drivers/scsi/cxlflash/main.h | 5 +-
2 files changed, 93 insertions(+), 42 deletions(-)
diff --git a/drivers/scsi/cxlflash/main.c b/drivers/scsi/cxlflash/main.c
index 35968bd..e6d56ac 100644
--- a/drivers/scsi/cxlflash/main.c
+++ b/drivers/scsi/cxlflash/main.c
@@ -683,28 +683,23 @@ static void stop_afu(struct cxlflash_cfg *cfg)
}
/**
- * term_mc() - terminates the master context
+ * term_intr() - disables all AFU interrupts
* @cfg: Internal structure associated with the host.
* @level: Depth of allocation, where to begin waterfall tear down.
*
* Safe to call with AFU/MC in partially allocated/initialized state.
*/
-static void term_mc(struct cxlflash_cfg *cfg, enum undo_level level)
+static void term_intr(struct cxlflash_cfg *cfg, enum undo_level level)
{
- int rc = 0;
struct afu *afu = cfg->afu;
struct device *dev = &cfg->dev->dev;
if (!afu || !cfg->mcctx) {
- dev_err(dev, "%s: returning from term_mc with NULL afu or MC\n",
- __func__);
+ dev_err(dev, "%s: returning with NULL afu or MC\n", __func__);
return;
}
switch (level) {
- case UNDO_START:
- rc = cxl_stop_context(cfg->mcctx);
- BUG_ON(rc);
case UNMAP_THREE:
cxl_unmap_afu_irq(cfg->mcctx, 3, afu);
case UNMAP_TWO:
@@ -713,9 +708,34 @@ static void term_mc(struct cxlflash_cfg *cfg, enum undo_level level)
cxl_unmap_afu_irq(cfg->mcctx, 1, afu);
case FREE_IRQ:
cxl_free_afu_irqs(cfg->mcctx);
- case RELEASE_CONTEXT:
- cfg->mcctx = NULL;
+ /* fall through */
+ case UNDO_NOOP:
+ /* No action required */
+ break;
+ }
+}
+
+/**
+ * term_mc() - terminates the master context
+ * @cfg: Internal structure associated with the host.
+ * @level: Depth of allocation, where to begin waterfall tear down.
+ *
+ * Safe to call with AFU/MC in partially allocated/initialized state.
+ */
+static void term_mc(struct cxlflash_cfg *cfg)
+{
+ int rc = 0;
+ struct afu *afu = cfg->afu;
+ struct device *dev = &cfg->dev->dev;
+
+ if (!afu || !cfg->mcctx) {
+ dev_err(dev, "%s: returning with NULL afu or MC\n", __func__);
+ return;
}
+
+ rc = cxl_stop_context(cfg->mcctx);
+ WARN_ON(rc);
+ cfg->mcctx = NULL;
}
/**
@@ -726,10 +746,20 @@ static void term_mc(struct cxlflash_cfg *cfg, enum undo_level level)
*/
static void term_afu(struct cxlflash_cfg *cfg)
{
+ /*
+ * Tear down is carefully orchestrated to ensure
+ * no interrupts can come in when the problem state
+ * area is unmapped.
+ *
+ * 1) Disable all AFU interrupts
+ * 2) Unmap the problem state area
+ * 3) Stop the master context
+ */
+ term_intr(cfg, UNMAP_THREE);
if (cfg->afu)
stop_afu(cfg);
- term_mc(cfg, UNDO_START);
+ term_mc(cfg);
pr_debug("%s: returning\n", __func__);
}
@@ -1597,41 +1627,24 @@ static int start_afu(struct cxlflash_cfg *cfg)
}
/**
- * init_mc() - create and register as the master context
+ * init_intr() - setup interrupt handlers for the master context
* @cfg: Internal structure associated with the host.
*
* Return: 0 on success, -errno on failure
*/
-static int init_mc(struct cxlflash_cfg *cfg)
+static enum undo_level init_intr(struct cxlflash_cfg *cfg,
+ struct cxl_context *ctx)
{
- struct cxl_context *ctx;
- struct device *dev = &cfg->dev->dev;
struct afu *afu = cfg->afu;
+ struct device *dev = &cfg->dev->dev;
int rc = 0;
- enum undo_level level;
-
- ctx = cxl_get_context(cfg->dev);
- if (unlikely(!ctx))
- return -ENOMEM;
- cfg->mcctx = ctx;
-
- /* Set it up as a master with the CXL */
- cxl_set_master(ctx);
-
- /* During initialization reset the AFU to start from a clean slate */
- rc = cxl_afu_reset(cfg->mcctx);
- if (unlikely(rc)) {
- dev_err(dev, "%s: initial AFU reset failed rc=%d\n",
- __func__, rc);
- level = RELEASE_CONTEXT;
- goto out;
- }
+ enum undo_level level = UNDO_NOOP;
rc = cxl_allocate_afu_irqs(ctx, 3);
if (unlikely(rc)) {
dev_err(dev, "%s: call to allocate_afu_irqs failed rc=%d!\n",
__func__, rc);
- level = RELEASE_CONTEXT;
+ level = UNDO_NOOP;
goto out;
}
@@ -1661,8 +1674,47 @@ static int init_mc(struct cxlflash_cfg *cfg)
level = UNMAP_TWO;
goto out;
}
+out:
+ return level;
+}
- rc = 0;
+/**
+ * init_mc() - create and register as the master context
+ * @cfg: Internal structure associated with the host.
+ *
+ * Return: 0 on success, -errno on failure
+ */
+static int init_mc(struct cxlflash_cfg *cfg)
+{
+ struct cxl_context *ctx;
+ struct device *dev = &cfg->dev->dev;
+ int rc = 0;
+ enum undo_level level;
+
+ ctx = cxl_get_context(cfg->dev);
+ if (unlikely(!ctx)) {
+ rc = -ENOMEM;
+ goto ret;
+ }
+ cfg->mcctx = ctx;
+
+ /* Set it up as a master with the CXL */
+ cxl_set_master(ctx);
+
+ /* During initialization reset the AFU to start from a clean slate */
+ rc = cxl_afu_reset(cfg->mcctx);
+ if (unlikely(rc)) {
+ dev_err(dev, "%s: initial AFU reset failed rc=%d\n",
+ __func__, rc);
+ goto ret;
+ }
+
+ level = init_intr(cfg, ctx);
+ if (unlikely(level)) {
+ dev_err(dev, "%s: setting up interrupts failed rc=%d\n",
+ __func__, rc);
+ goto out;
+ }
/* This performs the equivalent of the CXL_IOCTL_START_WORK.
* The CXL_IOCTL_GET_PROCESS_ELEMENT is implicit in the process
@@ -1678,7 +1730,7 @@ ret:
pr_debug("%s: returning rc=%d\n", __func__, rc);
return rc;
out:
- term_mc(cfg, level);
+ term_intr(cfg, level);
goto ret;
}
@@ -1751,7 +1803,8 @@ out:
err2:
kref_put(&afu->mapcount, afu_unmap);
err1:
- term_mc(cfg, UNDO_START);
+ term_intr(cfg, UNMAP_THREE);
+ term_mc(cfg);
goto out;
}
@@ -2488,8 +2541,7 @@ static pci_ers_result_t cxlflash_pci_error_detected(struct pci_dev *pdev,
if (unlikely(rc))
dev_err(dev, "%s: Failed to mark user contexts!(%d)\n",
__func__, rc);
- stop_afu(cfg);
- term_mc(cfg, UNDO_START);
+ term_afu(cfg);
return PCI_ERS_RESULT_NEED_RESET;
case pci_channel_io_perm_failure:
cfg->state = STATE_FAILTERM;
diff --git a/drivers/scsi/cxlflash/main.h b/drivers/scsi/cxlflash/main.h
index 0faed42..eb9d8f7 100644
--- a/drivers/scsi/cxlflash/main.h
+++ b/drivers/scsi/cxlflash/main.h
@@ -79,12 +79,11 @@
#define WWPN_BUF_LEN (WWPN_LEN + 1)
enum undo_level {
- RELEASE_CONTEXT = 0,
+ UNDO_NOOP = 0,
FREE_IRQ,
UNMAP_ONE,
UNMAP_TWO,
- UNMAP_THREE,
- UNDO_START
+ UNMAP_THREE
};
struct dev_dependent_vals {
--
2.1.0
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