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

From: Alexey Kardashevskiy <[email-masked]>
Date: Thu, 09 Apr 2015 13:21:40 +1000

On 04/09/2015 01:43 AM, Alex Williamson wrote:
> On Wed, 2015-04-08 at 13:22 +1000, Alexey Kardashevskiy wrote:
>> On 04/03/2015 07:50 AM, Alex Williamson wrote:
>>>
>>> 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
>>
>> Out of curiosity - why? Is every single implementation is known for
>> checking the argument?
>
> AFAIK, all flavors of free in the kernel accept NULL pointers and do the
> right thing.  I verified this one does too.
>
>>>> +		vfree(tbl->it_userspace);
>>>> +
>>>
>>> Why no NULL setting this time?
>>
>> iommu_reset_table() (2 lines below) will do memset(0) on the entire struct.
>
> So then should iommu_reset_table() handle the vfree() as well?

I wanted to keep vfree() in the same file with vzalloc(). Bad idea?
But I'll move vfree() to iommu_reset_table() anyway.

>
>>>>    	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,
>>>>    };
>>>
>>>
>>>
>>
>>
>> Thanks for the review! What is overall resume? Another respin?
>
> Is there another option?  It seems like there are too many issues to
> simply fold cleanups onto the end of the series.  Thanks,

I'll repost indeed, I meant it would help me if you could tell that you 
agree with the patchset and Ben can pull this stuff to his tree. Thanks!

-- 
Alexey