The existing implementation accounts the whole DMA window in
the locked_vm counter. This is going to be worse with multiple
containers and huge DMA windows. Also, real-time accounting would requite
additional tracking of accounted pages due to the page size difference -
IOMMU uses 4K pages and system uses 4K or 64K pages.
Another issue is that actual pages pinning/unpinning happens on every
DMA map/unmap request. This does not affect the performance much now as
we spend way too much time now on switching context between
guest/userspace/host but this will start to matter when we add in-kernel
DMA map/unmap acceleration.
This introduces a new IOMMU type for SPAPR - VFIO_SPAPR_TCE_v2_IOMMU.
New IOMMU deprecates VFIO_IOMMU_ENABLE/VFIO_IOMMU_DISABLE and introduces
2 new ioctls to register/unregister DMA memory -
VFIO_IOMMU_SPAPR_REGISTER_MEMORY and VFIO_IOMMU_SPAPR_UNREGISTER_MEMORY -
which receive user space address and size of a memory region which
needs to be pinned/unpinned and counted in locked_vm.
New IOMMU splits physical pages pinning and TCE table update
into 2 different operations. It requires:
1) guest pages to be registered first
2) consequent map/unmap requests to work only with pre-registered memory.
For the default single window case this means that the entire guest
(instead of 2GB) needs to be pinned before using VFIO.
When a huge DMA window is added, no additional pinning will be
required, otherwise it would be guest RAM + 2GB.
The new memory registration ioctls are not supported by
VFIO_SPAPR_TCE_IOMMU. Dynamic DMA window and in-kernel acceleration
will require memory to be preregistered in order to work.
The accounting is done per the user process.
This advertises v2 SPAPR TCE IOMMU and restricts what the userspace
can do with v1 or v2 IOMMUs.
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).
As v2 IOMMU supports IODA2 and pre-IODA2 IOMMUs (which do not support
DDW API), this creates a default DMA window for IODA2 for consistency.
Signed-off-by: Alexey Kardashevskiy
[aw: for the vfio related changes]
Acked-by: Alex Williamson
---
Changes:
v12:
* tce_iommu_unregister_pages() is fixed to use mm_iommu_find() which
enforces the requirement to unregister exactly the same region which
was registered (not overlapped)
* added a clause about creating default DMA window on IODA2
v11:
* mm_iommu_put() does not return a code so this does not check it
* moved "v2" in tce_container to pack the struct
v10:
* moved it_userspace allocation to vfio_iommu_spapr_tce as it VFIO
specific thing
* squashed "powerpc/iommu: Add userspace view of TCE table" into this as
it is
a part of IOMMU v2
* s/tce_iommu_use_page_v2/tce_iommu_prereg_ua_to_hpa/
* fixed some function names to have "tce_iommu_" in the beginning rather
just "tce_"
* as mm_iommu_mapped_inc() can now fail, check for the return code
v9:
* s/tce_get_hva_cached/tce_iommu_use_page_v2/
v7:
* now memory is registered per mm (i.e. process)
* moved memory registration code to powerpc/mmu
* merged "vfio: powerpc/spapr: Define v2 IOMMU" into this
* limited new ioctls to v2 IOMMU
* updated doc
* unsupported ioclts return -ENOTTY instead of -EPERM
v6:
* tce_get_hva_cached() returns hva via a pointer
v4:
* updated docs
* s/kzmalloc/vzalloc/
* in tce_pin_pages()/tce_unpin_pages() removed @vaddr, @size and
replaced offset with index
* renamed vfio_iommu_type_register_memory to vfio_iommu_spapr_register_memory
and removed duplicating vfio_iommu_spapr_register_memory
---
Documentation/vfio.txt | 31 ++-
arch/powerpc/include/asm/iommu.h| 6 +
drivers/vfio/vfio_iommu_spapr_tce.c | 513 ++--
include/uapi/linux/vfio.h | 27 ++
4 files changed, 488 insertions(+), 89 deletions(-)
diff --git a/Documentation/vfio.txt b/Documentation/vfio.txt
index 96978ec..7dcf2b5 100644
--- a/Documentation/vfio.txt
+++ b/Documentation/vfio.txt
@@ -289,10 +289,12 @@ PPC64 sPAPR implementation note
This implementation has some specifics:
-1) Only one IOMMU group per container is supported as an IOMMU group
-represents the minimal entity which isolation can be guaranteed for and
-groups are allocated statically, one per a Partitionable Endpoint (PE)
+1) On older systems (POWER7 with P5IOC2/IODA1) only one IOMMU group per
+container is supported as an IOMMU table is allocated at the boot time,
+one table per a IOMMU group which is a Partitionable Endpoint (PE)
(PE is often a PCI domain but not always).
+Newer systems (POWER8 with IODA2) have improved
