Re: [PATCH kernel] powerpc/powernv/ioda: Store correct amount of memory used for table

[David Gibson <david@gibson.dropbear.id.au>]

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On Mon, Feb 11, 2019 at 06:48:01PM +1100, Alexey Kardashevskiy wrote:
> We store 2 multilevel tables in iommu_table - one for the hardware and
> one with the corresponding userspace addresses. Before allocating
> the tables, the iommu_table_group_ops::get_table_size() hook returns
> the combined size of the two and VFIO SPAPR TCE IOMMU driver adjusts
> the locked_vm counter correctly. When the table is actually allocated,
> the amount of allocated memory is stored in iommu_table::it_allocated_size
> and used to adjust the locked_vm counter when we release the memory used
> by the table; .get_table_size() and .create_table() calculate it
> independently but the result is expected to be the same.

Any way we can remove that redundant calculation?  That seems like
begging for bugs.

> Unfortunately the allocator does not add the userspace table size to
> ::it_allocated_size so when we destroy the table because of VFIO PCI
> unplug (i.e. VFIO container is gone but the userspace keeps running),
> we decrement locked_vm by just a half of size of memory we are releasing.
> As the result, we leak locked_vm and may not be able to allocate more
> IOMMU tables after few iterations of hotplug/unplug.
> 
> This adjusts it_allocated_size if the userspace addresses table was
> requested (total_allocated_uas is initialized by zero).
> 
> Fixes: 090bad39b "powerpc/powernv: Add indirect levels to it_userspace"
> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

> ---
>  arch/powerpc/platforms/powernv/pci-ioda-tce.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/powerpc/platforms/powernv/pci-ioda-tce.c b/arch/powerpc/platforms/powernv/pci-ioda-tce.c
> index 697449a..58146e1 100644
> --- a/arch/powerpc/platforms/powernv/pci-ioda-tce.c
> +++ b/arch/powerpc/platforms/powernv/pci-ioda-tce.c
> @@ -313,7 +313,7 @@ long pnv_pci_ioda2_table_alloc_pages(int nid, __u64 bus_offset,
>  			page_shift);
>  	tbl->it_level_size = 1ULL << (level_shift - 3);
>  	tbl->it_indirect_levels = levels - 1;
> -	tbl->it_allocated_size = total_allocated;
> +	tbl->it_allocated_size = total_allocated + total_allocated_uas;
>  	tbl->it_userspace = uas;
>  	tbl->it_nid = nid;
>  

-- 
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

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