Subject: Re: [PATCH 6/8] powerpc/eeh: Initialize EEH address cache earlier

From: Oliver O'Halloran <[email-masked]>
Date: Thu, 18 Apr 2019 20:13:53 +1000

On Wed, 2019-03-20 at 13:58 +1100, Sam Bobroff wrote:
> The EEH address cache is currently initialized and populated by a
> single function: eeh_addr_cache_build().  While the initial population
> of the cache can only be done once resources are allocated,
> initialization (just setting up a spinlock) could be done much
> earlier.
> 
> So move the initialization step into a separate function and call it
> from a core_initcall (rather than a subsys initcall).
> 

> This will allow future work to make use of the cache during boot time
> PCI scanning.

What's the idea there? Checking for overlaps in the BAR assignments?

> Signed-off-by: Sam Bobroff <[email-masked]>
> ---
>  arch/powerpc/include/asm/eeh.h  |  3 +++
>  arch/powerpc/kernel/eeh.c       |  2 ++
>  arch/powerpc/kernel/eeh_cache.c | 13 +++++++++++--
>  3 files changed, 16 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/eeh.h b/arch/powerpc/include/asm/eeh.h
> index e217ccda55d0..791b9e6fcc45 100644
> --- a/arch/powerpc/include/asm/eeh.h
> +++ b/arch/powerpc/include/asm/eeh.h
> @@ -295,6 +295,7 @@ int __init eeh_ops_register(struct eeh_ops *ops);
>  int __exit eeh_ops_unregister(const char *name);
>  int eeh_check_failure(const volatile void __iomem *token);
>  int eeh_dev_check_failure(struct eeh_dev *edev);
> +void eeh_addr_cache_init(void);
>  void eeh_addr_cache_build(void);
>  void eeh_add_device_early(struct pci_dn *);
>  void eeh_add_device_tree_early(struct pci_dn *);
> @@ -362,6 +363,8 @@ static inline int eeh_check_failure(const volatile void __iomem *token)
>  
>  #define eeh_dev_check_failure(x) (0)
>  
> +static inline void eeh_addr_cache_init(void) { }
> +
>  static inline void eeh_addr_cache_build(void) { }
>  
>  static inline void eeh_add_device_early(struct pci_dn *pdn) { }
> diff --git a/arch/powerpc/kernel/eeh.c b/arch/powerpc/kernel/eeh.c
> index 3dcff29cb9b3..7a406d58d2c0 100644
> --- a/arch/powerpc/kernel/eeh.c
> +++ b/arch/powerpc/kernel/eeh.c
> @@ -1219,6 +1219,8 @@ static int eeh_init(void)
>  	list_for_each_entry_safe(hose, tmp, &hose_list, list_node)
>  		eeh_dev_phb_init_dynamic(hose);
>  
> +	eeh_addr_cache_init();
> +
>  	/* Initialize EEH event */
>  	return eeh_event_init();
>  }
> diff --git a/arch/powerpc/kernel/eeh_cache.c b/arch/powerpc/kernel/eeh_cache.c
> index 9c68f0837385..f93dd5cf6a39 100644
> --- a/arch/powerpc/kernel/eeh_cache.c
> +++ b/arch/powerpc/kernel/eeh_cache.c
> @@ -267,6 +267,17 @@ void eeh_addr_cache_rmv_dev(struct pci_dev *dev)
>  	spin_unlock_irqrestore(&pci_io_addr_cache_root.piar_lock, flags);
>  }
>  
> +/**
> + * eeh_addr_cache_init - Initialize a cache of I/O addresses
> + *
> + * Initialize a cache of pci i/o addresses.  This cache will be used to
> + * find the pci device that corresponds to a given address.
> + */
> +void eeh_addr_cache_init(void)
> +{
> +	spin_lock_init(&pci_io_addr_cache_root.piar_lock);
> +}

You could move this out of the pci_io_addr_cache structure and use
DEFINE_SPINLOCK() too. We might even be able to get rid of the hand-
rolled interval tree in eeh_cache.c in favour of the generic
implementation (see mm/interval_tree.c). I'm pretty sure the generic
one is a drop-in replacement, but I haven't had a chance to have a
detailed look to see if there's any differences in behaviour.

> +
>  /**
>   * eeh_addr_cache_build - Build a cache of I/O addresses
>   *
> @@ -282,8 +293,6 @@ void eeh_addr_cache_build(void)
>  	struct eeh_dev *edev;
>  	struct pci_dev *dev = NULL;
>  
> -	spin_lock_init(&pci_io_addr_cache_root.piar_lock);
> -
>  	for_each_pci_dev(dev) {
>  		pdn = pci_get_pdn_by_devfn(dev->bus, dev->devfn);
>  		if (!pdn)