| Message ID | 20190213033818.51452-1-aik@ozlabs.ru (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 11f5acce2fa43b015a8120fa7620fa4efd0a2952 |
| Headers | show |
| Series | [kernel,v2] powerpc/powernv/ioda: Fix locked_vm counting for memory used by IOMMU tables | expand |
| Context | Check | Description |
|---|---|---|
| snowpatch_ozlabs/apply_patch | success | next/apply_patch Successfully applied |
| snowpatch_ozlabs/build-ppc64le | success | build succeeded & removed 0 sparse warning(s) |
| snowpatch_ozlabs/build-ppc64be | success | build succeeded & removed 0 sparse warning(s) |
| snowpatch_ozlabs/build-ppc64e | success | build succeeded & removed 0 sparse warning(s) |
| snowpatch_ozlabs/build-pmac32 | success | build succeeded & removed 0 sparse warning(s) |
| snowpatch_ozlabs/checkpatch | warning | total: 0 errors, 0 warnings, 1 checks, 21 lines checked |
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)
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)
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(-)