From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e34.co.us.ibm.com (e34.co.us.ibm.com [32.97.110.152]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id F0BFF1A013A for ; Thu, 18 Sep 2014 05:45:14 +1000 (EST) Received: from /spool/local by e34.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 17 Sep 2014 13:45:12 -0600 Received: from b03cxnp08027.gho.boulder.ibm.com (b03cxnp08027.gho.boulder.ibm.com [9.17.130.19]) by d03dlp01.boulder.ibm.com (Postfix) with ESMTP id 553861FF003F for ; Wed, 17 Sep 2014 13:45:09 -0600 (MDT) Received: from d03av03.boulder.ibm.com (d03av03.boulder.ibm.com [9.17.195.169]) by b03cxnp08027.gho.boulder.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id s8HJjAt549741900 for ; Wed, 17 Sep 2014 21:45:10 +0200 Received: from d03av03.boulder.ibm.com (localhost [127.0.0.1]) by d03av03.boulder.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id s8HJj9mV004222 for ; Wed, 17 Sep 2014 13:45:09 -0600 Message-ID: <5419E4C4.4000305@linux.vnet.ibm.com> Date: Wed, 17 Sep 2014 14:45:08 -0500 From: Nathan Fontenot MIME-Version: 1.0 To: Michael Ellerman Subject: Re: [4/5] pseries: Implement memory hotplug add in the kernel References: <54174CF3.1010802@linux.vnet.ibm.com> <1410937639.27681.12.camel@concordia> In-Reply-To: <1410937639.27681.12.camel@concordia> Content-Type: text/plain; charset=utf-8 Cc: linuxppc-dev@lists.ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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 >> --- >> 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 >> #include >> #include >> +#include >> >> #include >> #include >> @@ -24,6 +25,8 @@ >> #include >> #include >> >> +#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