Re: [PATCH v2 00/24] iommu: Refactor DMA domain strictness
From: chenxiang (M)
Date: Thu Jul 29 2021 - 21:23:42 EST
在 2021/7/29 18:59, Robin Murphy 写道:
On 2021-07-29 03:55, chenxiang (M) wrote:
Hi Robin,
在 2021/7/28 23:58, Robin Murphy 写道:
Hi all,
Here's v2 where things start to look more realistic, hence the expanded
CC list. The patches are now based on the current iommu/core branch to
take John's iommu_set_dma_strict() cleanup into account.
The series remiains in two (or possibly 3) logical parts - for people
CC'd on cookie cleanup patches, the later parts should not affect you
since your drivers don't implement non-strict mode anyway; the cleanup
is all pretty straightforward, but please do yell at me if I've managed
to let a silly mistake slip through and broken your driver.
This time I have also build-tested x86 as well as arm64 :)
I have tested those patchset on ARM64 with SMMUV3, and the testcases
are as follows:
- Boot with iommu.strict=0, running fio and it works well;
- Boot with iommu.strict=1, running fio and it works well;
- Change strict mode to lazy mode when building, the change takes
effect;
- Boot without iommu.strict(default strict mode), change the sysfs
interface type from DMA to DMA-FQ dynamically during running fio, and
it works well;
- Boot without iommu.strict(default strict mode), change the sysfs
interface type from DMA-FQ to DMA dynamically, and it is not allowed
and print "Device or resource busy"
(i know it is qualified, and we can change no-strict mode to strict
by unbind the driver -> change the sysfs interface (type)->bind the
driver (tested this and it works well),
but i have a small question: is it also possible to change from
DMA-FQ to DMA dynamically? )
As patch #22 mentions, I think it's possible in principle, but it's
certainly trickier. When enabling a flush queue, it doesn't matter if
it takes a while for other threads to notice that cookie->fq_domain is
now set and stop doing synchronous invalidations (and in the SMMU case
it seems like there are probably enough dependencies to additionally
prevent the io_pgtable quirk being observable before that). However
when disabling, we'd need to be absolutely sure that the driver *has*
started invalidating strictly before we stop queueing freed IOVAs,
plus we need to be absolutely sure that we've stopped queueing freed
IOVAs before we attempt to tear down the flush queue itself. I'm not
sure off-hand how feasible it would be to put all that synchronisation
in the right places without it also impacting normal operation.
Furthermore, as also noted, there doesn't seem to be a good reason for
ever actually needing to do that. If a device isn't trusted, it should
be given a strict domain *before* any driver has a chance to start
doing anything, or your trust model is broken and pretty useless. I
can imagine some niche debugging/benchmarking cases where it might
help save a bit of effort, but nothing with a strong enough
justification to be worth supporting in mainline.
Ok, thanks.
Anyway, please feel free to add :
Tested-by: Xiang Chen <chenxiang66@xxxxxxxxxxxxx>
That's great, thanks!
Robin.
Changes in v2:
- Add iommu_is_dma_domain() helper to abstract flag check (and help
avoid silly typos like the one in v1).
- Tweak a few commit messages for spelling and (hopefully) clarity.
- Move the iommu_create_device_direct_mappings() update to patch #14
where it should have been.
- Rewrite patch #20 as a conversion of the now-existing option.
- Clean up the ops->flush_iotlb_all check which is also made redundant
by the new domain type
- Add patch #24, which is arguably tangential, but it was something I
spotted during the rebase, so...
Once again, the whole lot is available on a branch here:
https://gitlab.arm.com/linux-arm/linux-rm/-/tree/iommu/fq
Thanks,
Robin.
CC: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
CC: Yoshihiro Shimoda <yoshihiro.shimoda.uh@xxxxxxxxxxx>
CC: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
CC: Yong Wu <yong.wu@xxxxxxxxxxxx>
CC: Heiko Stuebner <heiko@xxxxxxxxx>
CC: Chunyan Zhang <chunyan.zhang@xxxxxxxxxx>
CC: Chunyan Zhang <chunyan.zhang@xxxxxxxxxx>
CC: Maxime Ripard <mripard@xxxxxxxxxx>
CC: Jean-Philippe Brucker <jean-philippe@xxxxxxxxxx>
Robin Murphy (24):
iommu: Pull IOVA cookie management into the core
iommu/amd: Drop IOVA cookie management
iommu/arm-smmu: Drop IOVA cookie management
iommu/vt-d: Drop IOVA cookie management
iommu/exynos: Drop IOVA cookie management
iommu/ipmmu-vmsa: Drop IOVA cookie management
iommu/mtk: Drop IOVA cookie management
iommu/rockchip: Drop IOVA cookie management
iommu/sprd: Drop IOVA cookie management
iommu/sun50i: Drop IOVA cookie management
iommu/virtio: Drop IOVA cookie management
iommu/dma: Unexport IOVA cookie management
iommu/dma: Remove redundant "!dev" checks
iommu: Introduce explicit type for non-strict DMA domains
iommu/amd: Prepare for multiple DMA domain types
iommu/arm-smmu: Prepare for multiple DMA domain types
iommu/vt-d: Prepare for multiple DMA domain types
iommu: Express DMA strictness via the domain type
iommu: Expose DMA domain strictness via sysfs
iommu: Merge strictness and domain type configs
iommu/dma: Factor out flush queue init
iommu: Allow enabling non-strict mode dynamically
iommu/arm-smmu: Allow non-strict in pgtable_quirks interface
iommu: Only log strictness for DMA domains
.../ABI/testing/sysfs-kernel-iommu_groups | 2 +
drivers/iommu/Kconfig | 80
+++++++++----------
drivers/iommu/amd/iommu.c | 21 +----
drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 25 ++++--
drivers/iommu/arm/arm-smmu/arm-smmu.c | 29 ++++---
drivers/iommu/arm/arm-smmu/qcom_iommu.c | 8 --
drivers/iommu/dma-iommu.c | 44 +++++-----
drivers/iommu/exynos-iommu.c | 18 +----
drivers/iommu/intel/iommu.c | 23 ++----
drivers/iommu/iommu.c | 53 +++++++-----
drivers/iommu/ipmmu-vmsa.c | 27 +------
drivers/iommu/mtk_iommu.c | 6 --
drivers/iommu/rockchip-iommu.c | 11 +--
drivers/iommu/sprd-iommu.c | 6 --
drivers/iommu/sun50i-iommu.c | 12 +--
drivers/iommu/virtio-iommu.c | 8 --
include/linux/dma-iommu.h | 9 ++-
include/linux/iommu.h | 15 +++-
18 files changed, 171 insertions(+), 226 deletions(-)
.