On 09/17/2014 02:07 AM, Michael Ellerman wrote:
>
> On Mon, 2014-09-15 at 15:32 -0500, Nathan Fontenot wrote:
>> This patch adds the ability to do memory hotplug adding 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 <nf...@linux.vnet.ibm.com>
>> ---
>> arch/powerpc/platforms/pseries/hotplug-memory.c | 170
>> +++++++++++++++++++++++
>> 1 file changed, 170 insertions(+)
>>
>> diff --git a/arch/powerpc/platforms/pseries/hotplug-memory.c
>> b/arch/powerpc/platforms/pseries/hotplug-memory.c
>> index 0e60e15..b254773 100644
>> --- a/arch/powerpc/platforms/pseries/hotplug-memory.c
>> +++ b/arch/powerpc/platforms/pseries/hotplug-memory.c
>> @@ -17,6 +17,7 @@
>> #include <linux/vmalloc.h>
>> #include <linux/memory.h>
>> #include <linux/memory_hotplug.h>
>> +#include <linux/slab.h>
>>
>> #include <asm/firmware.h>
>> #include <asm/machdep.h>
>> @@ -24,6 +25,8 @@
>> #include <asm/sparsemem.h>
>> #include <asm/rtas.h>
>>
>> +#include "pseries.h"
>> +
>> DEFINE_MUTEX(dlpar_mem_mutex);
>>
>> unsigned long pseries_memory_block_size(void)
>> @@ -69,6 +72,53 @@ unsigned long pseries_memory_block_size(void)
>> return memblock_size;
>> }
>>
>> +static void dlpar_free_drconf_property(struct property *prop)
>> +{
>> + kfree(prop->name);
>> + kfree(prop->value);
>> + kfree(prop);
>> +}
>> +
>> +static struct property *dlpar_clone_drconf_property(struct device_node *dn)
>> +{
>> + struct property *prop, *new_prop;
>> +
>> + prop = of_find_property(dn, "ibm,dynamic-memory", NULL);
>> + if (!prop)
>> + return NULL;
>> +
>> + new_prop = kzalloc(sizeof(*new_prop), GFP_KERNEL);
>> + if (!new_prop)
>> + return NULL;
>> +
>> + new_prop->name = kstrdup(prop->name, GFP_KERNEL);
>> + new_prop->value = kmalloc(prop->length + 1, GFP_KERNEL);
>> + if (!new_prop->name || !new_prop->value) {
>> + dlpar_free_drconf_property(new_prop);
>> + return NULL;
>> + }
>> +
>> + memcpy(new_prop->value, prop->value, prop->length);
>> + new_prop->length = prop->length;
>> + *(((char *)new_prop->value) + new_prop->length) = 0;
>
> It's not a string, is it?
No, property->value is a void*. I'll drop that line of code.
>
>> + return new_prop;
>> +}
>> +
>> +static struct memory_block *lmb_to_memblock(struct of_drconf_cell *lmb)
>> +{
>> + unsigned long section_nr;
>> + struct mem_section *mem_sect;
>> + struct memory_block *mem_block;
>> + u64 phys_addr = be64_to_cpu(lmb->base_addr);
>> +
>> + section_nr = pfn_to_section_nr(PFN_DOWN(phys_addr));
>> + mem_sect = __nr_to_section(section_nr);
>> +
>> + mem_block = find_memory_block(mem_sect);
>> + return mem_block;
>> +}
>> +
>> #ifdef CONFIG_MEMORY_HOTREMOVE
>> static int pseries_remove_memory(u64 start, u64 size)
>> {
>> @@ -155,13 +205,133 @@ static inline int pseries_remove_mem_node(struct
>> device_node *np)
>> }
>> #endif /* CONFIG_MEMORY_HOTREMOVE */
>>
>> +static int dlpar_add_one_lmb(struct of_drconf_cell *lmb)
>> +{
>> + struct memory_block *mem_block;
>> + u64 phys_addr;
>> + unsigned long pages_per_block;
>> + unsigned long block_sz;
>> + int nid, sections_per_block;
>> + int rc;
>> +
>> + phys_addr = be64_to_cpu(lmb->base_addr);
>
> of_drconf_cell needs endian annotations.
Yes it does. I can include a patch to update the struct.
>
>> + block_sz = memory_block_size_bytes();
>> + sections_per_block = block_sz / MIN_MEMORY_BLOCK_SIZE;
>> + pages_per_block = PAGES_PER_SECTION * sections_per_block;
>> +
>> + if (phys_addr & ((pages_per_block << PAGE_SHIFT) - 1))
>> + return -EINVAL;
>> +
>> + nid = memory_add_physaddr_to_nid(phys_addr);
>> + rc = add_memory(nid, phys_addr, block_sz);
>> + if (rc)
>> + return rc;
>> +
>> + rc = memblock_add(phys_addr, block_sz);
>> + if (rc) {
>> + remove_memory(nid, phys_addr, block_sz);
>> + return rc;
>> + }
>> +
>> + mem_block = lmb_to_memblock(lmb);
>> + if (!mem_block) {
>> + remove_memory(nid, phys_addr, block_sz);
>> + return -EINVAL;
>> + }
>
> That could all use a lot of comments. ie. why do we have to add it twice?
We don't actually add it twice, though I can see how one could think
that based on the names of the routines called. I'll add comments to
clarify this in v2 of the patch.
memory_add_physaddr_to_nid(), this doesn't add anything despite its naming.
The routine finds the node id for the specified physical address.
add_memory(), this actually adds the memory.
memblock_add(), this informs the memory block information tracking about the
newly added memory. Why this is not done as part of add_memory I don't know.
>
>> + rc = device_online(&mem_block->dev);
>> + put_device(&mem_block->dev);
>> + if (rc)
>> + remove_memory(nid, phys_addr, block_sz);
>> +
>> + return rc;
>> +}
>> +
>> +static int dlpar_memory_add(struct pseries_hp_errorlog *hp_elog)
>> +{
>> + struct of_drconf_cell *lmb;
>> + struct device_node *dn;
>> + struct property *prop;
>> + uint32_t entries, *p;
>
> *p should be __be32.
Yes.
>
>> + int i, lmbs_to_add;
>> + int lmbs_added = 0;
>> + int rc = -EINVAL;
>
> Don't pre-initialise your rc variables.
I did this here for a reason. When asking to add memory by drc_index it
is possible to fall out of the for() loop traversing the lmb entries
and not find the requested drc_index.
Adding a check for this situation after the loop would do the same thing
and probably make this situation more clear.
>
>> + if (hp_elog->id_type == PSERIES_HP_ELOG_ID_DRC_COUNT) {
>> + lmbs_to_add = be32_to_cpu(hp_elog->_drc_u.drc_count);
>> + pr_info("Attempting to hot-add %d LMB(s)\n", lmbs_to_add);
>> + } else {
>> + lmbs_to_add = 1;
>> + pr_info("Attempting to hot-add LMB, drc index %x\n",
>> + be32_to_cpu(hp_elog->_drc_u.drc_index));
>> + }
>> +
>> + dn = of_find_node_by_path("/ibm,dynamic-reconfiguration-memory");
>> + if (!dn)
>> + return -EINVAL;
>> +
>> + prop = dlpar_clone_drconf_property(dn);
>> + if (!prop) {
>> + of_node_put(dn);
>> + return -EINVAL;
>> + }
>> +
>> + p = prop->value;
>> + entries = be32_to_cpu(*p++);
>> + lmb = (struct of_drconf_cell *)p;
>
>
> So if I'm reading this right the hp_elog either contains an index or a count
> of
> LMBs to add. But it doesn't contain anything about which address ranges to add
> or any of those details. That is all in the ibm,dynamic-memory property - but
> how did it get in there?
The ibm,dynamic-memory property of the device tree is passed to the kernel
by phyp/qemu. The property is an array that associates each LMB with a
starting physical address and associativity.
>
>> +
>> + for (i = 0; i < entries; i++, lmb++) {
>> + u32 drc_index = be32_to_cpu(lmb->drc_index);
>> +
>> + if (lmbs_to_add == lmbs_added)
>> + break;
>> +
>> + if (be32_to_cpu(lmb->flags) & DRCONF_MEM_ASSIGNED)
>> + continue;
>> +
>> + if (hp_elog->id_type == PSERIES_HP_ELOG_ID_DRC_INDEX
>> + && lmb->drc_index != hp_elog->_drc_u.drc_index)
>> + continue;
>> +
>> + rc = dlpar_acquire_drc(drc_index);
>> + if (rc)
>> + continue;
>> +
>> + rc = dlpar_add_one_lmb(lmb);
>> + if (rc) {
>> + dlpar_release_drc(drc_index);
>> + continue;
>> + }
>
> In both the above error cases you just move along. That means we potentially
> hotplugged some memory but not everything that we were asked to. That seems
> like a bad idea, we should either do everything or nothing.
>
>
That can be done, though will require some additional tracking.
The current hotplug handling for PowerVM make a best effort and tries to
add/remove as much of the requested memory as possible. I was going with
that same approach here, but have no problem moving to an all or nothing
approach.
We will need to keep track of the LMBs added/removed during a request so
we can return to the original state if the request cannot be satisfied.
>> +
>> + lmb->flags |= cpu_to_be32(DRCONF_MEM_ASSIGNED);
>> + lmbs_added++;
>> + pr_info("Memory at %llx (drc index %x) has been hot-added\n",
>> + be64_to_cpu(lmb->base_addr), drc_index);
>> + }
>> +
>> + if (lmbs_added)
>> + rc = of_update_property(dn, prop);
>> + else
>> + dlpar_free_drconf_property(prop);
>
> The value of rc here is not clear. It could be EINVAL or it could be the
> result
> of the last dlpar_add_one_lmb(lmb). gcc would have told you that if you hadn't
> initialised it.
>
>> +
>> + of_node_put(dn);
>> + return rc ? rc : lmbs_added;
>
> This looks wrong.
>
> Doesn't the rc eventually go back to dlpar_write(), which expects 0 for
> success?
>
> That should show up as the write failing in userspace.
>
>
Based on previous comments I think the handling of rc will be updated so
we either return success or failure.
>> int dlpar_memory(struct pseries_hp_errorlog *hp_elog)
>> {
>> int rc = 0;
>
> Don't initialise to zero, that way gcc can tell you if there's a path where
> you
> forget to initialise it. It also means you can't accidentally return success.
>
>> + if (hp_elog->id_type != PSERIES_HP_ELOG_ID_DRC_COUNT
>> + && hp_elog->id_type != PSERIES_HP_ELOG_ID_DRC_INDEX)
>> + return -EINVAL;
>
> This would look nicer as a switch I think.
can do.
-Nathan
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