Subject: Re: [PATCH kernel v9 27/32] powerpc/iommu/ioda2: Add get_table_size() to calculate the size of future table

From: David Gibson <[email-masked]>
Date: Wed, 29 Apr 2015 16:40:29 +1000

On Sat, Apr 25, 2015 at 10:14:51PM +1000, Alexey Kardashevskiy wrote:
> This adds a way for the IOMMU user to know how much a new table will
> use so it can be accounted in the locked_vm limit before allocation
> happens.
> 
> This stores the allocated table size in pnv_pci_create_table()
> so the locked_vm counter can be updated correctly when a table is
> being disposed.
> 
> This defines an iommu_table_group_ops callback to let VFIO know
> how much memory will be locked if a table is created.
> 
> Signed-off-by: Alexey Kardashevskiy <[email-masked]>
> ---
> Changes:
> v9:
> * reimplemented the whole patch
> ---
>  arch/powerpc/include/asm/iommu.h          |  5 +++++
>  arch/powerpc/platforms/powernv/pci-ioda.c | 14 ++++++++++++
>  arch/powerpc/platforms/powernv/pci.c      | 36 +++++++++++++++++++++++++++++++
>  arch/powerpc/platforms/powernv/pci.h      |  2 ++
>  4 files changed, 57 insertions(+)
> 
> diff --git a/arch/powerpc/include/asm/iommu.h b/arch/powerpc/include/asm/iommu.h
> index 1472de3..9844c106 100644
> --- a/arch/powerpc/include/asm/iommu.h
> +++ b/arch/powerpc/include/asm/iommu.h
> @@ -99,6 +99,7 @@ struct iommu_table {
>  	unsigned long  it_size;      /* Size of iommu table in entries */
>  	unsigned long  it_indirect_levels;
>  	unsigned long  it_level_size;
> +	unsigned long  it_allocated_size;
>  	unsigned long  it_offset;    /* Offset into global table */
>  	unsigned long  it_base;      /* mapped address of tce table */
>  	unsigned long  it_index;     /* which iommu table this is */
> @@ -155,6 +156,10 @@ extern struct iommu_table *iommu_init_table(struct iommu_table * tbl,
>  struct iommu_table_group;
>  
>  struct iommu_table_group_ops {
> +	unsigned long (*get_table_size)(
> +			__u32 page_shift,
> +			__u64 window_size,
> +			__u32 levels);
>  	long (*create_table)(struct iommu_table_group *table_group,
>  			int num,
>  			__u32 page_shift,
> diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c
> index e0be556..7f548b4 100644
> --- a/arch/powerpc/platforms/powernv/pci-ioda.c
> +++ b/arch/powerpc/platforms/powernv/pci-ioda.c
> @@ -2062,6 +2062,18 @@ static void pnv_pci_ioda2_setup_bypass_pe(struct pnv_phb *phb,
>  }
>  
>  #ifdef CONFIG_IOMMU_API
> +static unsigned long pnv_pci_ioda2_get_table_size(__u32 page_shift,
> +		__u64 window_size, __u32 levels)
> +{
> +	unsigned long ret = pnv_get_table_size(page_shift, window_size, levels);
> +
> +	if (!ret)
> +		return ret;
> +
> +	/* Add size of it_userspace */
> +	return ret + (window_size >> page_shift) * sizeof(unsigned long);

This doesn't make much sense.  The userspace view can't possibly be a
property of the specific low-level IOMMU model.

> +}
> +
>  static long pnv_pci_ioda2_create_table(struct iommu_table_group *table_group,
>  		int num, __u32 page_shift, __u64 window_size, __u32 levels,
>  		struct iommu_table *tbl)
> @@ -2086,6 +2098,7 @@ static long pnv_pci_ioda2_create_table(struct iommu_table_group *table_group,
>  
>  	BUG_ON(tbl->it_userspace);
>  	tbl->it_userspace = uas;
> +	tbl->it_allocated_size += uas_cb;
>  	tbl->it_ops = &pnv_ioda2_iommu_ops;
>  	if (pe->tce_inval_reg)
>  		tbl->it_type |= (TCE_PCI_SWINV_CREATE | TCE_PCI_SWINV_FREE);
> @@ -2160,6 +2173,7 @@ static void pnv_ioda2_release_ownership(struct iommu_table_group *table_group)
>  }
>  
>  static struct iommu_table_group_ops pnv_pci_ioda2_ops = {
> +	.get_table_size = pnv_pci_ioda2_get_table_size,
>  	.create_table = pnv_pci_ioda2_create_table,
>  	.set_window = pnv_pci_ioda2_set_window,
>  	.unset_window = pnv_pci_ioda2_unset_window,
> diff --git a/arch/powerpc/platforms/powernv/pci.c b/arch/powerpc/platforms/powernv/pci.c
> index fc129c4..1b5b48a 100644
> --- a/arch/powerpc/platforms/powernv/pci.c
> +++ b/arch/powerpc/platforms/powernv/pci.c
> @@ -662,6 +662,38 @@ void pnv_pci_setup_iommu_table(struct iommu_table *tbl,
>  	tbl->it_type = TCE_PCI;
>  }
>  
> +unsigned long pnv_get_table_size(__u32 page_shift,
> +		__u64 window_size, __u32 levels)
> +{
> +	unsigned long bytes = 0;
> +	const unsigned window_shift = ilog2(window_size);
> +	unsigned entries_shift = window_shift - page_shift;
> +	unsigned table_shift = entries_shift + 3;
> +	unsigned long tce_table_size = max(0x1000UL, 1UL << table_shift);
> +	unsigned long direct_table_size;
> +
> +	if (!levels || (levels > POWERNV_IOMMU_MAX_LEVELS) ||
> +			(window_size > memory_hotplug_max()) ||
> +			!is_power_of_2(window_size))
> +		return 0;
> +
> +	/* Calculate a direct table size from window_size and levels */
> +	entries_shift = ROUND_UP(entries_shift, levels) / levels;
> +	table_shift = entries_shift + 3;
> +	table_shift = max_t(unsigned, table_shift, PAGE_SHIFT);
> +	direct_table_size =  1UL << table_shift;
> +
> +	for ( ; levels; --levels) {
> +		bytes += ROUND_UP(tce_table_size, direct_table_size);
> +
> +		tce_table_size /= direct_table_size;
> +		tce_table_size <<= 3;
> +		tce_table_size = ROUND_UP(tce_table_size, direct_table_size);
> +	}
> +
> +	return bytes;
> +}
> +
>  static __be64 *pnv_alloc_tce_table_pages(int nid, unsigned shift,
>  		unsigned levels, unsigned long limit,
>  		unsigned long *tce_table_allocated)
> @@ -741,6 +773,10 @@ long pnv_pci_create_table(struct iommu_table_group *table_group, int nid,
>  		return -ENOMEM;
>  	}
>  
> +	tbl->it_allocated_size = pnv_get_table_size(page_shift, window_size,
> +			levels);
> +	WARN_ON(!tbl->it_allocated_size);
> +
>  	/* Setup linux iommu table */
>  	pnv_pci_setup_iommu_table(tbl, addr, tce_table_size, bus_offset,
>  			page_shift);
> diff --git a/arch/powerpc/platforms/powernv/pci.h b/arch/powerpc/platforms/powernv/pci.h
> index 3d1ff584..ce4bc3c 100644
> --- a/arch/powerpc/platforms/powernv/pci.h
> +++ b/arch/powerpc/platforms/powernv/pci.h
> @@ -224,6 +224,8 @@ extern long pnv_pci_create_table(struct iommu_table_group *table_group, int nid,
>  		__u64 bus_offset, __u32 page_shift, __u64 window_size,
>  		__u32 levels, struct iommu_table *tbl);
>  extern void pnv_pci_free_table(struct iommu_table *tbl);
> +extern unsigned long pnv_get_table_size(__u32 page_shift,
> +		__u64 window_size, __u32 levels);
>  extern void pnv_pci_init_p5ioc2_hub(struct device_node *np);
>  extern void pnv_pci_init_ioda_hub(struct device_node *np);
>  extern void pnv_pci_init_ioda2_phb(struct device_node *np);

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson