Subject: Re: [PATCH v2 3/6] pseries: Create new device hotplug entry point

From: Nathan Fontenot <[email-masked]>
Date: Tue, 18 Nov 2014 12:18:17 -0600

On 11/17/2014 04:53 PM, Gavin Shan wrote:
> On Mon, Nov 17, 2014 at 03:51:42PM -0600, Nathan Fontenot wrote:
>> Create a new entry point for device hotplug on pseries that will
>> work for both PowerVM and PowerKVM systems.
>>
>> The current process to hotplug (or dlpar) devices (generally the same
>> process for memory, cpu, and pci devices) on PowerVM systems is initiated
>>from the HMC, which communicates the request to the partitions through
>> the RSCT framework. The RSCT framework then invokes the drmgr command.
>> The drmgr command performs the hotplug operation by doing some pieces,
>> such as most of the rtas calls and device tree parsing, in userspace
>> and make requests to the kernel to online/offline the device, update the
>> device tree and add/remove the device.
>>
>> For PowerKVM the approach for device hotplug is to follow what is currently
>> being done for pci hotplug. A hotplug request is initiated from the host,
>> QEMU then generates an EPOW interrupt to the guest which causes the guest
>> to make the rtas,check-exception call. In QEMU, the rtas,check-exception call
>> returns a rtas hotplug event to the guest.
>>
>> Please note that the current pci hotplug path for PowerKVM involves the
>> kernel receiving the rtas hotplug event, passing it to rtas_errd in
>> userspace, and having rtas_errd invoke drmgr. The drmgr command then
>> handles the request as described above for PowerVM systems. This is to
>> be updated to perform pci completely in the kernel in a later patch set.
>>
>> There is no need for this circuitous route, we should handle the entire
>> hotplug of devices in the kernel. What I am planning is to enable this
>> by moving the code to handle device hotplug from drmgr into the kernel to
>> provide a single path for both PowerVM and PowerKVM systems. This patch
>> provides the common entry point. For PowerKVM a future update to the kernel
>> rtas code will recognize rtas hotplug events returned from
>> rtas,check-exception calls and use the common entry point to handle device
>> hotplug entirely in the kernel.
>>
>> For PowerVM systems, this patch creates the /sys/kernel/dlpar file that rtas
>> hotplug events can be written to by drmgr and passed to the common entry point.
>> There is no chance of updating how we receive hotplug requests on PowerVM
>> systems.
>>
>> Signed-off-by: Nathan Fontenot <[email-masked]>
>> ---
>> arch/powerpc/platforms/pseries/dlpar.c          |   72 ++++++++++++++++++++++-
>> arch/powerpc/platforms/pseries/hotplug-memory.c |   19 ++++++
>> arch/powerpc/platforms/pseries/pseries.h        |   10 +++
>> 3 files changed, 99 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/powerpc/platforms/pseries/dlpar.c b/arch/powerpc/platforms/pseries/dlpar.c
>> index c22bb1b..ec825d3 100644
>> --- a/arch/powerpc/platforms/pseries/dlpar.c
>> +++ b/arch/powerpc/platforms/pseries/dlpar.c
>> @@ -10,6 +10,8 @@
>>  * 2 as published by the Free Software Foundation.
>>  */
>>
>> +#define pr_fmt(fmt)	"dlpar: " fmt
>> +
>> #include <linux/kernel.h>
>> #include <linux/notifier.h>
>> #include <linux/spinlock.h>
>> @@ -535,13 +537,79 @@ static ssize_t dlpar_cpu_release(const char *buf, size_t count)
>> 	return count;
>> }
>>
>> +#endif /* CONFIG_ARCH_CPU_PROBE_RELEASE */
>> +
>> +static int handle_dlpar_errorlog(struct rtas_error_log *error_log)
>> +{
>> +	struct pseries_errorlog *pseries_log;
>> +	struct pseries_hp_errorlog *hp_elog;
>> +	int rc;
>> +
>> +	pseries_log = get_pseries_errorlog(error_log,
>> +					   PSERIES_ELOG_SECT_ID_HOTPLUG);
>> +	if (!pseries_log || (pseries_log->length == 0))
>> +		return -EINVAL;
>> +
>> +	hp_elog = (struct pseries_hp_errorlog *)pseries_log->data;
>> +
>> +	/* Go ahead and convert the hotplug type to the correct endianness
>> +	 * to avoid converting it everywhere we use it.
>> +	 */
>> +	switch (hp_elog->id_type) {
>> +	case PSERIES_HP_ELOG_ID_DRC_COUNT:
>> +		hp_elog->_drc_u.drc_count =
>> +					be32_to_cpu(hp_elog->_drc_u.drc_count);
>> +	case PSERIES_HP_ELOG_ID_DRC_INDEX:
>> +		hp_elog->_drc_u.drc_index =
>> +					be32_to_cpu(hp_elog->_drc_u.drc_index);
>> +	}
>> +
> 
> It seems that "break" was missed for all cases.

Yep, it was.

> 
>> +	switch (hp_elog->resource) {
>> +	case PSERIES_HP_ELOG_RESOURCE_MEM:
>> +		rc = dlpar_memory(hp_elog);
>> +		break;
>> +	default:
>> +		pr_warn_ratelimited("Invalid resource (%d) specified\n",
>> +				    hp_elog->resource);
>> +		rc = -EINVAL;
>> +		break;
> 
> Unnecessary "break" here.

I'll remove this one and send an updated patch.

-Nathan

> 
>> +	}
>> +
>> +	return rc;
>> +}
>> +
>> +static ssize_t dlpar_store(struct file *filp, struct kobject *kobj,
>> +			   struct bin_attribute *bin_attr, char *buf,
>> +			   loff_t pos, size_t count)
>> +{
>> +	struct rtas_error_log *error_log;
>> +	int rc;
>> +
>> +	error_log = kmalloc(count, GFP_KERNEL);
>> +	if (!error_log)
>> +		return -ENOMEM;
>> +
>> +	memcpy(error_log, buf, count);
>> +
>> +	rc = handle_dlpar_errorlog(error_log);
>> +	kfree(error_log);
>> +	return rc ? rc : count;
>> +}
>> +
>> +static BIN_ATTR(dlpar, S_IWUSR, NULL, dlpar_store, 0);
>> +
>> static int __init pseries_dlpar_init(void)
>> {
>> +	int rc;
>> +
>> +#ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
>> 	ppc_md.cpu_probe = dlpar_cpu_probe;
>> 	ppc_md.cpu_release = dlpar_cpu_release;
>> +#endif /* CONFIG_ARCH_CPU_PROBE_RELEASE */
>>
>> -	return 0;
>> +	rc = sysfs_create_bin_file(kernel_kobj, &bin_attr_dlpar);
>> +
>> +	return rc;
>> }
>> machine_device_initcall(pseries, pseries_dlpar_init);
>>
>> -#endif /* CONFIG_ARCH_CPU_PROBE_RELEASE */
>> diff --git a/arch/powerpc/platforms/pseries/hotplug-memory.c b/arch/powerpc/platforms/pseries/hotplug-memory.c
>> index 3cb256c..69d178b 100644
>> --- a/arch/powerpc/platforms/pseries/hotplug-memory.c
>> +++ b/arch/powerpc/platforms/pseries/hotplug-memory.c
>> @@ -9,6 +9,8 @@
>>  *      2 of the License, or (at your option) any later version.
>>  */
>>
>> +#define pr_fmt(fmt)	"pseries-hotplug-mem: " fmt
>> +
>> #include <linux/of.h>
>> #include <linux/of_address.h>
>> #include <linux/memblock.h>
>> @@ -134,6 +136,23 @@ static inline int pseries_remove_mem_node(struct device_node *np)
>> }
>> #endif /* CONFIG_MEMORY_HOTREMOVE */
>>
>> +int dlpar_memory(struct pseries_hp_errorlog *hp_elog)
>> +{
>> +	int rc = 0;
>> +
>> +	lock_device_hotplug();
>> +
>> +	switch (hp_elog->action) {
>> +	default:
>> +		pr_err("Invalid action (%d) specified\n", hp_elog->action);
>> +		rc = -EINVAL;
>> +		break;
>> +	}
>> +
>> +	unlock_device_hotplug();
>> +	return rc;
>> +}
>> +
>> static int pseries_add_mem_node(struct device_node *np)
>> {
>> 	const char *type;
>> diff --git a/arch/powerpc/platforms/pseries/pseries.h b/arch/powerpc/platforms/pseries/pseries.h
>> index 239bee5..40e0339 100644
>> --- a/arch/powerpc/platforms/pseries/pseries.h
>> +++ b/arch/powerpc/platforms/pseries/pseries.h
>> @@ -11,6 +11,7 @@
>> #define _PSERIES_PSERIES_H
>>
>> #include <linux/interrupt.h>
>> +#include <asm/rtas.h>
>>
>> struct device_node;
>>
>> @@ -63,6 +64,15 @@ extern int dlpar_detach_node(struct device_node *);
>> int dlpar_acquire_drc(u32 drc_index);
>> int dlpar_release_drc(u32 drc_index);
>>
>> +#ifdef CONFIG_MEMORY_HOTPLUG
>> +int dlpar_memory(struct pseries_hp_errorlog *hp_elog);
>> +#else
>> +static inline int dlpar_memory(struct pseries_hp_errorlog *hp_elog)
>> +{
>> +	return -EOPNOTSUPP;
>> +}
>> +#endif
>> +
>> /* PCI root bridge prepare function override for pseries */
>> struct pci_host_bridge;
>> int pseries_root_bridge_prepare(struct pci_host_bridge *bridge);
>>
>> _______________________________________________
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> 
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