Re: [5/5] pseries: Implement memory hotplug remove in the kernel

On 09/17/2014 02:07 AM, Michael Ellerman wrote:

On Mon, 2014-09-15 at 15:33 -0500, Nathan Fontenot wrote:

quoted

This patch adds the ability to do memory hotplug remove in the kernel.

Currently the hotplug add/remove of memory is handled by the drmgr
command. The drmgr command performs the add/remove by performing
some work in user-space and making requests to the kernel to handle
other pieces. By moving all of the work to the kernel we can do the
add and remove faster, and provide a common place to do memory hotplug
for both the PowerVM and PowerKVM environments.

Signed-off-by: Nathan Fontenot <redacted>
---
 arch/powerpc/platforms/pseries/hotplug-memory.c |  140 +++++++++++++++++++++++
 1 file changed, 139 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/platforms/pseries/hotplug-memory.c b/arch/powerpc/platforms/pseries/hotplug-memory.c
index b254773..160c424 100644
--- a/arch/powerpc/platforms/pseries/hotplug-memory.c
+++ b/arch/powerpc/platforms/pseries/hotplug-memory.c

@@ -193,7 +193,137 @@ static int pseries_remove_mem_node(struct device_node *np)
 	pseries_remove_memblock(base, lmb_size);
 	return 0;
 }
+
+static int lmb_is_removable(struct of_drconf_cell *lmb)
+{

Do we not already have something like this?

No. Perhaps your thinking of the code in drivers/base/memory.c that
handles the sysfs removable file. That code just calls the same
is_mem_section_removable() routine.

quoted

+	int i, scns_per_block;
+	int rc = 1;

I can see this makes the &= work below.

But what if block_sz / MIN_MEMORY_BLOCK_SIZE = 0 ?

If that happens, something else is really wrong. Most
likely a malformed device tree.

For pseries MIN_MEMORY_BLOCK_SIZE is defined to be the smallest
LMB size we suppport, 16MB.

I can add a pr_warn() statement here and bail if that happens.

quoted

+	unsigned long pfn, block_sz;
+	u64 phys_addr;
+
+	phys_addr = be64_to_cpu(lmb->base_addr);
+	block_sz = memory_block_size_bytes();
+	scns_per_block = block_sz / MIN_MEMORY_BLOCK_SIZE;
+
+	for (i = 0; i < scns_per_block; i++) {
+		pfn = PFN_DOWN(phys_addr);
+		if (!pfn_present(pfn))
+			continue;
+
+		rc &= is_mem_section_removable(pfn, PAGES_PER_SECTION);
+		phys_addr += MIN_MEMORY_BLOCK_SIZE;
+	}
+
+	return rc;
+}

quoted

+static int dlpar_memory_remove(struct pseries_hp_errorlog *hp_elog)
+{

...

quoted

+}

Most of the same comments as for add.

ok, I'll go through them and apply them to the remove code.

Thanks for the review.

-Nathan