[1/2] powerpc: Allow memory that has been hot-removed to be hot-added

Message ID 20180803060601.724-1-rashmica.g@gmail.com
State Accepted
Commit d3da701d3308ce1fa457f32c6c9e2102aedea030
Headers show
Series
  • [1/2] powerpc: Allow memory that has been hot-removed to be hot-added
Related show

Checks

Context Check Description
snowpatch_ozlabs/checkpatch success Test checkpatch on branch next
snowpatch_ozlabs/apply_patch success next/apply_patch Successfully applied

Commit Message

Rashmica Gupta Aug. 3, 2018, 6:06 a.m.
This patch allows the memory removed by memtrace to be readded to the
kernel. So now you don't have to reboot your system to add the memory
back to the kernel or to have a different amount of memory removed.

Signed-off-by: Rashmica Gupta <rashmica.g@gmail.com>
---
To remove 1GB from each node:
echo 1073741824  >  /sys/kernel/debug/powerpc/memtrace/enable

To add this memory back and remove 2GB:
echo 2147483648 >  /sys/kernel/debug/powerpc/memtrace/enable 

To just re-add memory:
echo 0  >  /sys/kernel/debug/powerpc/memtrace/enable 


 arch/powerpc/platforms/powernv/memtrace.c | 93 ++++++++++++++++++++++++++++---
 1 file changed, 86 insertions(+), 7 deletions(-)

Comments

Michael Neuling Aug. 7, 2018, 6:52 a.m. | #1
On Fri, 2018-08-03 at 16:06 +1000, Rashmica Gupta wrote:
> This patch allows the memory removed by memtrace to be readded to the
> kernel. So now you don't have to reboot your system to add the memory
> back to the kernel or to have a different amount of memory removed.
> 
> Signed-off-by: Rashmica Gupta <rashmica.g@gmail.com>

Tested-by: Michael Neuling <mikey@neuling.org>

> ---
> To remove 1GB from each node:
> echo 1073741824  >  /sys/kernel/debug/powerpc/memtrace/enable
> 
> To add this memory back and remove 2GB:
> echo 2147483648 >  /sys/kernel/debug/powerpc/memtrace/enable 
> 
> To just re-add memory:
> echo 0  >  /sys/kernel/debug/powerpc/memtrace/enable 

Nice... thanks!

Mikey

> 
> 
>  arch/powerpc/platforms/powernv/memtrace.c | 93 ++++++++++++++++++++++++++++
> ---
>  1 file changed, 86 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/powerpc/platforms/powernv/memtrace.c
> b/arch/powerpc/platforms/powernv/memtrace.c
> index b99283df8584..51fe0862dcab 100644
> --- a/arch/powerpc/platforms/powernv/memtrace.c
> +++ b/arch/powerpc/platforms/powernv/memtrace.c
> @@ -206,8 +206,11 @@ static int memtrace_init_debugfs(void)
>  
>  		snprintf(ent->name, 16, "%08x", ent->nid);
>  		dir = debugfs_create_dir(ent->name, memtrace_debugfs_dir);
> -		if (!dir)
> +		if (!dir) {
> +			pr_err("Failed to create debugfs directory for node
> %d\n",
> +				ent->nid);
>  			return -1;
> +		}
>  
>  		ent->dir = dir;
>  		debugfs_create_file("trace", 0400, dir, ent, &memtrace_fops);
> @@ -218,18 +221,94 @@ static int memtrace_init_debugfs(void)
>  	return ret;
>  }
>  
> +static int online_mem_block(struct memory_block *mem, void *arg)
> +{
> +	return device_online(&mem->dev);
> +}
> +
> +/*
> + * Iterate through the chunks of memory we have removed from the kernel
> + * and attempt to add them back to the kernel.
> + */
> +static int memtrace_online(void)
> +{
> +	int i, ret = 0;
> +	struct memtrace_entry *ent;
> +
> +	for (i = memtrace_array_nr - 1; i >= 0; i--) {
> +		ent = &memtrace_array[i];
> +
> +		/* We have onlined this chunk previously */
> +		if (ent->nid == -1)
> +			continue;
> +
> +		/* Remove from io mappings */
> +		if (ent->mem) {
> +			iounmap(ent->mem);
> +			ent->mem = 0;
> +		}
> +
> +		if (add_memory(ent->nid, ent->start, ent->size)) {
> +			pr_err("Failed to add trace memory to node %d\n",
> +					 ent->nid);
> +			ret += 1;
> +			continue;
> +		}
> +
> +		/*
> +		 * If kernel isn't compiled with the auto online option
> +		 * we need to online the memory ourselves.
> +		 */
> +		if (!memhp_auto_online) {
> +			walk_memory_range(PFN_DOWN(ent->start),
> +				PFN_UP(ent->start + ent->size - 1),
> +				NULL, online_mem_block);
> +		}
> +
> +		/*
> +		 * Memory was added successfully so clean up references to it
> +		 * so on reentry we can tell that this chunk was added.
> +		 */
> +		debugfs_remove_recursive(ent->dir);
> +		pr_info("Added trace memory back to node %d\n", ent->nid);
> +		ent->size = ent->start = ent->nid = -1;
> +	}
> +	if (ret)
> +		return ret;
> +
> +	/* If all chunks of memory were added successfully, reset globals */
> +	kfree(memtrace_array);
> +	memtrace_array = NULL;
> +	memtrace_size = 0;
> +	memtrace_array_nr = 0;
> +	return 0;
> +
> +}
> +
>  static int memtrace_enable_set(void *data, u64 val)
>  {
> -	if (memtrace_size)
> +	uint64_t bytes;
> +
> +	/*
> +	 * Don't attempt to do anything if size isn't aligned to a memory
> +	 * block or equal to zero.
> +	 */
> +	bytes = memory_block_size_bytes();
> +	if (val & (bytes - 1)) {
> +		pr_err("Value must be aligned with 0x%llx\n", bytes);
>  		return -EINVAL;
> +	}
>  
> -	if (!val)
> -		return -EINVAL;
> +	/* Re-add/online previously removed/offlined memory */
> +	if (memtrace_size) {
> +		if (memtrace_online())
> +			return -EAGAIN;
> +	}
>  
> -	/* Make sure size is aligned to a memory block */
> -	if (val & (memory_block_size_bytes() - 1))
> -		return -EINVAL;
> +	if (!val)
> +		return 0;
>  
> +	/* Offline and remove memory */
>  	if (memtrace_init_regions_runtime(val))
>  		return -EINVAL;
>
Michael Ellerman Aug. 13, 2018, 11:23 a.m. | #2
On Fri, 2018-08-03 at 06:06:00 UTC, Rashmica Gupta wrote:
> This patch allows the memory removed by memtrace to be readded to the
> kernel. So now you don't have to reboot your system to add the memory
> back to the kernel or to have a different amount of memory removed.
> 
> Signed-off-by: Rashmica Gupta <rashmica.g@gmail.com>
> Tested-by: Michael Neuling <mikey@neuling.org>

Series applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/d3da701d3308ce1fa457f32c6c9e21

cheers

Patch

diff --git a/arch/powerpc/platforms/powernv/memtrace.c b/arch/powerpc/platforms/powernv/memtrace.c
index b99283df8584..51fe0862dcab 100644
--- a/arch/powerpc/platforms/powernv/memtrace.c
+++ b/arch/powerpc/platforms/powernv/memtrace.c
@@ -206,8 +206,11 @@  static int memtrace_init_debugfs(void)
 
 		snprintf(ent->name, 16, "%08x", ent->nid);
 		dir = debugfs_create_dir(ent->name, memtrace_debugfs_dir);
-		if (!dir)
+		if (!dir) {
+			pr_err("Failed to create debugfs directory for node %d\n",
+				ent->nid);
 			return -1;
+		}
 
 		ent->dir = dir;
 		debugfs_create_file("trace", 0400, dir, ent, &memtrace_fops);
@@ -218,18 +221,94 @@  static int memtrace_init_debugfs(void)
 	return ret;
 }
 
+static int online_mem_block(struct memory_block *mem, void *arg)
+{
+	return device_online(&mem->dev);
+}
+
+/*
+ * Iterate through the chunks of memory we have removed from the kernel
+ * and attempt to add them back to the kernel.
+ */
+static int memtrace_online(void)
+{
+	int i, ret = 0;
+	struct memtrace_entry *ent;
+
+	for (i = memtrace_array_nr - 1; i >= 0; i--) {
+		ent = &memtrace_array[i];
+
+		/* We have onlined this chunk previously */
+		if (ent->nid == -1)
+			continue;
+
+		/* Remove from io mappings */
+		if (ent->mem) {
+			iounmap(ent->mem);
+			ent->mem = 0;
+		}
+
+		if (add_memory(ent->nid, ent->start, ent->size)) {
+			pr_err("Failed to add trace memory to node %d\n",
+					 ent->nid);
+			ret += 1;
+			continue;
+		}
+
+		/*
+		 * If kernel isn't compiled with the auto online option
+		 * we need to online the memory ourselves.
+		 */
+		if (!memhp_auto_online) {
+			walk_memory_range(PFN_DOWN(ent->start),
+				PFN_UP(ent->start + ent->size - 1),
+				NULL, online_mem_block);
+		}
+
+		/*
+		 * Memory was added successfully so clean up references to it
+		 * so on reentry we can tell that this chunk was added.
+		 */
+		debugfs_remove_recursive(ent->dir);
+		pr_info("Added trace memory back to node %d\n", ent->nid);
+		ent->size = ent->start = ent->nid = -1;
+	}
+	if (ret)
+		return ret;
+
+	/* If all chunks of memory were added successfully, reset globals */
+	kfree(memtrace_array);
+	memtrace_array = NULL;
+	memtrace_size = 0;
+	memtrace_array_nr = 0;
+	return 0;
+
+}
+
 static int memtrace_enable_set(void *data, u64 val)
 {
-	if (memtrace_size)
+	uint64_t bytes;
+
+	/*
+	 * Don't attempt to do anything if size isn't aligned to a memory
+	 * block or equal to zero.
+	 */
+	bytes = memory_block_size_bytes();
+	if (val & (bytes - 1)) {
+		pr_err("Value must be aligned with 0x%llx\n", bytes);
 		return -EINVAL;
+	}
 
-	if (!val)
-		return -EINVAL;
+	/* Re-add/online previously removed/offlined memory */
+	if (memtrace_size) {
+		if (memtrace_online())
+			return -EAGAIN;
+	}
 
-	/* Make sure size is aligned to a memory block */
-	if (val & (memory_block_size_bytes() - 1))
-		return -EINVAL;
+	if (!val)
+		return 0;
 
+	/* Offline and remove memory */
 	if (memtrace_init_regions_runtime(val))
 		return -EINVAL;