* [PATCH kernel v2] powerpc/powernv/ioda: Fix locked_vm counting for memory used by IOMMU tables
@ 2019-02-13 3:38 Alexey Kardashevskiy
2019-02-13 4:48 ` David Gibson
2019-02-28 9:21 ` [kernel, " Michael Ellerman
0 siblings, 2 replies; 3+ messages in thread
From: Alexey Kardashevskiy @ 2019-02-13 3:38 UTC (permalink / raw)
To: linuxppc-dev; +Cc: Alexey Kardashevskiy, David Gibson
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 decrement 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.
However 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.
To make things worse, since we enabled on-demain allocation of
indirect levels, it_allocated_size contains only the amount of memory
actually allocated at the table creation time which can just be
a fraction. It is not a problem with incrementing locked_vm (as
get_table_size() value is used) but it is with decrementing.
As the result, we leak locked_vm and may not be able to allocate more
IOMMU tables after few iterations of hotplug/unplug.
This sets it_allocated_size in the pnv_pci_ioda2_ops::create_table()
hook to what pnv_pci_ioda2_get_table_size() returns so from now on
we have a single place which calculates the maximum memory a table can
occupy. The original meaning of it_allocated_size is somewhat lost now
though.
We do not ditch it_allocated_size whatsoever here and we do not call
get_table_size() from vfio_iommu_spapr_tce.c when decrementing locked_vm
as we may have multiple IOMMU groups per container and even though they
all are supposed to have the same get_table_size() implementation,
there is a small chance for failure or confusion.
Fixes: 090bad39b "powerpc/powernv: Add indirect levels to it_userspace"
Fixes: a68bd1267 "powerpc/powernv/ioda: Allocate indirect TCE levels on demand"
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
---
Changes:
v2:
* this is reworked "[PATCH kernel] powerpc/powernv/ioda: Store correct amount of memory used for table"
---
arch/powerpc/platforms/powernv/pci-ioda-tce.c | 1 -
arch/powerpc/platforms/powernv/pci-ioda.c | 7 ++++++-
2 files changed, 6 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/platforms/powernv/pci-ioda-tce.c b/arch/powerpc/platforms/powernv/pci-ioda-tce.c
index 697449a..e28f03e 100644
--- a/arch/powerpc/platforms/powernv/pci-ioda-tce.c
+++ b/arch/powerpc/platforms/powernv/pci-ioda-tce.c
@@ -313,7 +313,6 @@ 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_userspace = uas;
tbl->it_nid = nid;
diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c
index 7db3119..d415739 100644
--- a/arch/powerpc/platforms/powernv/pci-ioda.c
+++ b/arch/powerpc/platforms/powernv/pci-ioda.c
@@ -2592,8 +2592,13 @@ static long pnv_pci_ioda2_create_table_userspace(
int num, __u32 page_shift, __u64 window_size, __u32 levels,
struct iommu_table **ptbl)
{
- return pnv_pci_ioda2_create_table(table_group,
+ long ret = pnv_pci_ioda2_create_table(table_group,
num, page_shift, window_size, levels, true, ptbl);
+
+ if (!ret)
+ (*ptbl)->it_allocated_size = pnv_pci_ioda2_get_table_size(
+ page_shift, window_size, levels);
+ return ret;
}
static void pnv_ioda2_take_ownership(struct iommu_table_group *table_group)
--
2.17.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH kernel v2] powerpc/powernv/ioda: Fix locked_vm counting for memory used by IOMMU tables
2019-02-13 3:38 [PATCH kernel v2] powerpc/powernv/ioda: Fix locked_vm counting for memory used by IOMMU tables Alexey Kardashevskiy
@ 2019-02-13 4:48 ` David Gibson
2019-02-28 9:21 ` [kernel, " Michael Ellerman
1 sibling, 0 replies; 3+ messages in thread
From: David Gibson @ 2019-02-13 4:48 UTC (permalink / raw)
To: Alexey Kardashevskiy; +Cc: linuxppc-dev
[-- Attachment #1: Type: text/plain, Size: 4363 bytes --]
On Wed, Feb 13, 2019 at 02:38:18PM +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 decrement 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.
>
> However 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.
>
> To make things worse, since we enabled on-demain allocation of
s/demain/demand/
> indirect levels, it_allocated_size contains only the amount of memory
> actually allocated at the table creation time which can just be
> a fraction. It is not a problem with incrementing locked_vm (as
> get_table_size() value is used) but it is with decrementing.
>
> As the result, we leak locked_vm and may not be able to allocate more
> IOMMU tables after few iterations of hotplug/unplug.
>
> This sets it_allocated_size in the pnv_pci_ioda2_ops::create_table()
> hook to what pnv_pci_ioda2_get_table_size() returns so from now on
> we have a single place which calculates the maximum memory a table can
> occupy. The original meaning of it_allocated_size is somewhat lost now
> though.
>
> We do not ditch it_allocated_size whatsoever here and we do not call
> get_table_size() from vfio_iommu_spapr_tce.c when decrementing locked_vm
> as we may have multiple IOMMU groups per container and even though they
> all are supposed to have the same get_table_size() implementation,
> there is a small chance for failure or confusion.
>
> Fixes: 090bad39b "powerpc/powernv: Add indirect levels to it_userspace"
> Fixes: a68bd1267 "powerpc/powernv/ioda: Allocate indirect TCE levels on demand"
> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Apart from the typo above,
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
> ---
> Changes:
> v2:
> * this is reworked "[PATCH kernel] powerpc/powernv/ioda: Store correct amount of memory used for table"
>
> ---
> arch/powerpc/platforms/powernv/pci-ioda-tce.c | 1 -
> arch/powerpc/platforms/powernv/pci-ioda.c | 7 ++++++-
> 2 files changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/arch/powerpc/platforms/powernv/pci-ioda-tce.c b/arch/powerpc/platforms/powernv/pci-ioda-tce.c
> index 697449a..e28f03e 100644
> --- a/arch/powerpc/platforms/powernv/pci-ioda-tce.c
> +++ b/arch/powerpc/platforms/powernv/pci-ioda-tce.c
> @@ -313,7 +313,6 @@ 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_userspace = uas;
> tbl->it_nid = nid;
>
> diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c
> index 7db3119..d415739 100644
> --- a/arch/powerpc/platforms/powernv/pci-ioda.c
> +++ b/arch/powerpc/platforms/powernv/pci-ioda.c
> @@ -2592,8 +2592,13 @@ static long pnv_pci_ioda2_create_table_userspace(
> int num, __u32 page_shift, __u64 window_size, __u32 levels,
> struct iommu_table **ptbl)
> {
> - return pnv_pci_ioda2_create_table(table_group,
> + long ret = pnv_pci_ioda2_create_table(table_group,
> num, page_shift, window_size, levels, true, ptbl);
> +
> + if (!ret)
> + (*ptbl)->it_allocated_size = pnv_pci_ioda2_get_table_size(
> + page_shift, window_size, levels);
> + return ret;
> }
>
> static void pnv_ioda2_take_ownership(struct iommu_table_group *table_group)
--
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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^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [kernel, v2] powerpc/powernv/ioda: Fix locked_vm counting for memory used by IOMMU tables
2019-02-13 3:38 [PATCH kernel v2] powerpc/powernv/ioda: Fix locked_vm counting for memory used by IOMMU tables Alexey Kardashevskiy
2019-02-13 4:48 ` David Gibson
@ 2019-02-28 9:21 ` Michael Ellerman
1 sibling, 0 replies; 3+ messages in thread
From: Michael Ellerman @ 2019-02-28 9:21 UTC (permalink / raw)
To: Alexey Kardashevskiy, linuxppc-dev; +Cc: Alexey Kardashevskiy, David Gibson
On Wed, 2019-02-13 at 03:38:18 UTC, 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 decrement 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.
>
> However 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.
>
> To make things worse, since we enabled on-demain allocation of
> indirect levels, it_allocated_size contains only the amount of memory
> actually allocated at the table creation time which can just be
> a fraction. It is not a problem with incrementing locked_vm (as
> get_table_size() value is used) but it is with decrementing.
>
> As the result, we leak locked_vm and may not be able to allocate more
> IOMMU tables after few iterations of hotplug/unplug.
>
> This sets it_allocated_size in the pnv_pci_ioda2_ops::create_table()
> hook to what pnv_pci_ioda2_get_table_size() returns so from now on
> we have a single place which calculates the maximum memory a table can
> occupy. The original meaning of it_allocated_size is somewhat lost now
> though.
>
> We do not ditch it_allocated_size whatsoever here and we do not call
> get_table_size() from vfio_iommu_spapr_tce.c when decrementing locked_vm
> as we may have multiple IOMMU groups per container and even though they
> all are supposed to have the same get_table_size() implementation,
> there is a small chance for failure or confusion.
>
> Fixes: 090bad39b "powerpc/powernv: Add indirect levels to it_userspace"
> Fixes: a68bd1267 "powerpc/powernv/ioda: Allocate indirect TCE levels on demand"
> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
> Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Applied to powerpc next, thanks.
https://git.kernel.org/powerpc/c/11f5acce2fa43b015a8120fa7620fa4e
cheers
^ permalink raw reply [flat|nested] 3+ messages in thread
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2019-02-13 4:48 ` David Gibson
2019-02-28 9:21 ` [kernel, " Michael Ellerman
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