[PATCH v2 1/3] dmaengine: dmatest: Prevent to run on misconfigured channel

[PATCH v2 1/3] dmaengine: dmatest: Prevent to run on misconfigured channel

[Andy Shevchenko]

From: Vladimir Murzin <vladimir.murzin@arm.com>

Andy reported that commit 6b41030fdc79 ("dmaengine: dmatest:
Restore default for channel") broke his scripts for the case
where "busy" channel is used for configuration with expectation
that run command would do nothing. Instead, behavior was
(unintentionally) changed to treat such case as under-configuration
and progress with defaults, i.e. run command would start a test
with default setting for channel (which would use all channels).

Restore original behavior with tracking status of channel setter
so we can distinguish between misconfigured and under-configured
cases in run command and act accordingly.

Fixes: 6b41030fdc79 ("dmaengine: dmatest: Restore default for channel")
Reported-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Tested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
Tested-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
v2: improve title and the commit message (Vinod), added tag (Peter)
 drivers/dma/dmatest.c | 26 +++++++++++++++++++++-----
 1 file changed, 21 insertions(+), 5 deletions(-)

diff --git a/drivers/dma/dmatest.c b/drivers/dma/dmatest.c
index b2790641370a..ac28d5eea913 100644
--- a/drivers/dma/dmatest.c
+++ b/drivers/dma/dmatest.c
@@ -129,6 +129,7 @@ struct dmatest_params {
  * @nr_channels:	number of channels under test
  * @lock:		access protection to the fields of this structure
  * @did_init:		module has been initialized completely
+ * @last_error:		test has faced configuration issues
  */
 static struct dmatest_info {
 	/* Test parameters */
@@ -137,6 +138,7 @@ static struct dmatest_info {
 	/* Internal state */
 	struct list_head	channels;
 	unsigned int		nr_channels;
+	int			last_error;
 	struct mutex		lock;
 	bool			did_init;
 } test_info = {
@@ -1202,10 +1204,22 @@ static int dmatest_run_set(const char *val, const struct kernel_param *kp)
 		return ret;
 	} else if (dmatest_run) {
 		if (!is_threaded_test_pending(info)) {
-			pr_info("No channels configured, continue with any\n");
-			if (!is_threaded_test_run(info))
-				stop_threaded_test(info);
-			add_threaded_test(info);
+			/*
+			 * We have nothing to run. This can be due to:
+			 */
+			ret = info->last_error;
+			if (ret) {
+				/* 1) Misconfiguration */
+				pr_err("Channel misconfigured, can't continue\n");
+				mutex_unlock(&info->lock);
+				return ret;
+			} else {
+				/* 2) We rely on defaults */
+				pr_info("No channels configured, continue with any\n");
+				if (!is_threaded_test_run(info))
+					stop_threaded_test(info);
+				add_threaded_test(info);
+			}
 		}
 		start_threaded_tests(info);
 	} else {
@@ -1222,7 +1236,7 @@ static int dmatest_chan_set(const char *val, const struct kernel_param *kp)
 	struct dmatest_info *info = &test_info;
 	struct dmatest_chan *dtc;
 	char chan_reset_val[20];
-	int ret = 0;
+	int ret;
 
 	mutex_lock(&info->lock);
 	ret = param_set_copystring(val, kp);
@@ -1277,12 +1291,14 @@ static int dmatest_chan_set(const char *val, const struct kernel_param *kp)
 		goto add_chan_err;
 	}
 
+	info->last_error = ret;
 	mutex_unlock(&info->lock);
 
 	return ret;
 
 add_chan_err:
 	param_set_copystring(chan_reset_val, kp);
+	info->last_error = ret;
 	mutex_unlock(&info->lock);
 
 	return ret;
-- 
2.28.0

[PATCH v2 2/3] dmaengine: dmatest: Check list for emptiness before access its last entry

[Andy Shevchenko]

After writing a garbage to the channel we get an Oops in dmatest_chan_set()
due to access to last entry in the empty list.

[  212.670672] BUG: unable to handle page fault for address: fffffff000000020
[  212.677562] #PF: supervisor read access in kernel mode
[  212.682702] #PF: error_code(0x0000) - not-present page
...
[  212.710074] RIP: 0010:dmatest_chan_set+0x149/0x2d0 [dmatest]
[  212.715739] Code: e8 cc f9 ff ff 48 8b 1d 0d 55 00 00 48 83 7b 10 00 0f 84 63 01 00 00 48 c7 c7 d0 65 4d c0 e8 ee 4a f5 e1 48 89 c6 48 8b 43 10 <48> 8b 40 20 48 8b 78 58 48 85 ff 0f 84 f5 00 00 00 e8 b1 41 f5 e1

Fix this by checking list for emptiness before accessing its last entry.

Fixes: d53513d5dc28 ("dmaengine: dmatest: Add support for multi channel testing")
Cc: Vladimir Murzin <vladimir.murzin@arm.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Tested-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
---
v2: added tag (Peter)
 drivers/dma/dmatest.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/dma/dmatest.c b/drivers/dma/dmatest.c
index ac28d5eea913..f04f32bdf8f7 100644
--- a/drivers/dma/dmatest.c
+++ b/drivers/dma/dmatest.c
@@ -1267,15 +1267,14 @@ static int dmatest_chan_set(const char *val, const struct kernel_param *kp)
 	add_threaded_test(info);
 
 	/* Check if channel was added successfully */
-	dtc = list_last_entry(&info->channels, struct dmatest_chan, node);
-
-	if (dtc->chan) {
+	if (!list_empty(&info->channels)) {
 		/*
 		 * if new channel was not successfully added, revert the
 		 * "test_channel" string to the name of the last successfully
 		 * added channel. exception for when users issues empty string
 		 * to channel parameter.
 		 */
+		dtc = list_last_entry(&info->channels, struct dmatest_chan, node);
 		if ((strcmp(dma_chan_name(dtc->chan), strim(test_channel)) != 0)
 		    && (strcmp("", strim(test_channel)) != 0)) {
 			ret = -EINVAL;
-- 
2.28.0

[PATCH v2 3/3] dmaengine: dmatest: Return boolean result directly in filter()

[Andy Shevchenko]

There is no need to have a conditional for boolean expression when
function returns bool. Drop unnecessary code and return boolean
result directly.

While at it, drop unneeded casting from void *.

Cc: Vladimir Murzin <vladimir.murzin@arm.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Tested-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
---
v2: added tag (Peter)
 drivers/dma/dmatest.c | 8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/drivers/dma/dmatest.c b/drivers/dma/dmatest.c
index f04f32bdf8f7..2575c8128d95 100644
--- a/drivers/dma/dmatest.c
+++ b/drivers/dma/dmatest.c
@@ -1070,13 +1070,7 @@ static int dmatest_add_channel(struct dmatest_info *info,
 
 static bool filter(struct dma_chan *chan, void *param)
 {
-	struct dmatest_params *params = param;
-
-	if (!dmatest_match_channel(params, chan) ||
-	    !dmatest_match_device(params, chan->device))
-		return false;
-	else
-		return true;
+	return dmatest_match_channel(param, chan) && dmatest_match_device(param, chan->device);
 }
 
 static void request_channels(struct dmatest_info *info,
-- 
2.28.0

Re: [PATCH v2 1/3] dmaengine: dmatest: Prevent to run on misconfigured channel

[Vinod Koul]

On 22-09-20, 14:58, Andy Shevchenko wrote:
> From: Vladimir Murzin <vladimir.murzin@arm.com>
> 
> Andy reported that commit 6b41030fdc79 ("dmaengine: dmatest:
> Restore default for channel") broke his scripts for the case
> where "busy" channel is used for configuration with expectation
> that run command would do nothing. Instead, behavior was
> (unintentionally) changed to treat such case as under-configuration
> and progress with defaults, i.e. run command would start a test
> with default setting for channel (which would use all channels).
> 
> Restore original behavior with tracking status of channel setter
> so we can distinguish between misconfigured and under-configured
> cases in run command and act accordingly.

Applied all, thanks

-- 
~Vinod