Subject: Re: [PATCH kernel v7 26/31] powerpc/iommu: Add userspace view of TCE table

From: Alex Williamson <[email-masked]>
Date: Thu, 02 Apr 2015 14:50:03 -0600

Should have sent this with the other comments, but found it hiding on my
desktop...

On Sat, 2015-03-28 at 01:55 +1100, Alexey Kardashevskiy wrote:
> In order to support memory pre-registration, we need a way to track
> the use of every registered memory region and only allow unregistration
> if a region is not in use anymore. So we need a way to tell from what
> region the just cleared TCE was from.
> 
> This adds a userspace view of the TCE table into iommu_table struct.
> It contains userspace address, one per TCE entry. The table is only
> allocated when the ownership over an IOMMU group is taken which means
> it is only used from outside of the powernv code (such as VFIO).
> 
> Signed-off-by: Alexey Kardashevskiy <[email-masked]>
> ---
>  arch/powerpc/include/asm/iommu.h          |  6 ++++++
>  arch/powerpc/kernel/iommu.c               |  7 +++++++
>  arch/powerpc/platforms/powernv/pci-ioda.c | 23 ++++++++++++++++++++++-
>  3 files changed, 35 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/powerpc/include/asm/iommu.h b/arch/powerpc/include/asm/iommu.h
> index 2c08c91..a768a4d 100644
> --- a/arch/powerpc/include/asm/iommu.h
> +++ b/arch/powerpc/include/asm/iommu.h
> @@ -106,9 +106,15 @@ struct iommu_table {
>  	unsigned long *it_map;       /* A simple allocation bitmap for now */
>  	unsigned long  it_page_shift;/* table iommu page size */
>  	struct iommu_table_group *it_group;
> +	unsigned long *it_userspace; /* userspace view of the table */
>  	struct iommu_table_ops *it_ops;
>  };
>  
> +#define IOMMU_TABLE_USERSPACE_ENTRY(tbl, entry) \
> +		((tbl)->it_userspace ? \
> +			&((tbl)->it_userspace[(entry) - (tbl)->it_offset]) : \
> +			NULL)
> +
>  /* Pure 2^n version of get_order */
>  static inline __attribute_const__
>  int get_iommu_order(unsigned long size, struct iommu_table *tbl)
> diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c
> index 0bcd988..82102d1 100644
> --- a/arch/powerpc/kernel/iommu.c
> +++ b/arch/powerpc/kernel/iommu.c
> @@ -38,6 +38,7 @@
>  #include <linux/pci.h>
>  #include <linux/iommu.h>
>  #include <linux/sched.h>
> +#include <linux/vmalloc.h>
>  #include <asm/io.h>
>  #include <asm/prom.h>
>  #include <asm/iommu.h>
> @@ -1069,6 +1070,9 @@ static int iommu_table_take_ownership(struct iommu_table *tbl)
>  		spin_unlock(&tbl->pools[i].lock);
>  	spin_unlock_irqrestore(&tbl->large_pool.lock, flags);
>  
> +	BUG_ON(tbl->it_userspace);
> +	tbl->it_userspace = vzalloc(sizeof(*tbl->it_userspace) * tbl->it_size);
> +

-ENOMEM?

>  	return 0;
>  }
>  
> @@ -1102,6 +1106,9 @@ static void iommu_table_release_ownership(struct iommu_table *tbl)
>  {
>  	unsigned long flags, i, sz = (tbl->it_size + 7) >> 3;
>  
> +	vfree(tbl->it_userspace);
> +	tbl->it_userspace = NULL;
> +
>  	spin_lock_irqsave(&tbl->large_pool.lock, flags);
>  	for (i = 0; i < tbl->nr_pools; i++)
>  		spin_lock(&tbl->pools[i].lock);
> diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c
> index bc36cf1..036f3c1 100644
> --- a/arch/powerpc/platforms/powernv/pci-ioda.c
> +++ b/arch/powerpc/platforms/powernv/pci-ioda.c
> @@ -26,6 +26,7 @@
>  #include <linux/iommu.h>
>  #include <linux/mmzone.h>
>  #include <linux/sizes.h>
> +#include <linux/vmalloc.h>
>  
>  #include <asm/mmzone.h>
>  #include <asm/sections.h>
> @@ -1469,6 +1470,9 @@ static void pnv_pci_free_table(struct iommu_table *tbl)
>  	if (!tbl->it_size)
>  		return;
>  
> +	if (tbl->it_userspace)

Not necessary

> +		vfree(tbl->it_userspace);
> +

Why no NULL setting this time?

>  	pnv_free_tce_table(tbl->it_base, size, tbl->it_indirect_levels);
>  	iommu_reset_table(tbl, "ioda2");
>  }
> @@ -1656,9 +1660,26 @@ static void pnv_ioda2_set_ownership(struct iommu_table_group *table_group,
>  	pnv_pci_ioda2_set_bypass(pe, !enable);
>  }
>  
> +static long pnv_pci_ioda2_create_table_with_uas(
> +		struct iommu_table_group *table_group,
> +		int num, __u32 page_shift, __u64 window_size, __u32 levels,
> +		struct iommu_table *tbl)
> +{
> +	long ret = pnv_pci_ioda2_create_table(table_group, num,
> +			page_shift, window_size, levels, tbl);
> +
> +	if (ret)
> +		return ret;
> +
> +	BUG_ON(tbl->it_userspace);
> +	tbl->it_userspace = vzalloc(sizeof(*tbl->it_userspace) * tbl->it_size);

-ENOMEM

> +
> +	return 0;
> +}
> +
>  static struct iommu_table_group_ops pnv_pci_ioda2_ops = {
>  	.set_ownership = pnv_ioda2_set_ownership,
> -	.create_table = pnv_pci_ioda2_create_table,
> +	.create_table = pnv_pci_ioda2_create_table_with_uas,
>  	.set_window = pnv_pci_ioda2_set_window,
>  	.unset_window = pnv_pci_ioda2_unset_window,
>  };