On 22.03.19 10:44, 'Lokesh' via Jailhouse wrote:
From: Lokesh Vutla <[email protected]>
A System Memory Management Unit(SMMU) performs a task analogous to a
CPU's MMU, translating addresses for device requests from system I/O
devices before the requests are passed into the system interconnect.
Implement a driver for SMMU v3 that maps and unmaps memory for specified
stream ids. This driver supports only stage 2 translation and right now
inmates cannot enable stage 1 translations. Because of this limitation,
only assignment of device to a guest VM is supported. For isolation and
scatter-gather features stage-1 translation should be clubbed along
with the existing driver.
What is meant with "scatter-gather features"?
This driver is implemented based on the following assumptions:
- Running on a Little endian 64 bit core compatible with ARM v8 architecture
- SMMU supporting only AARCH64 mode
- SMMU AARCH 64 stage 2 translation configurations are compatible with
ARMv8 VMSA. So re using the translation tables of CPU for SMMU.
Inorder to enable stage 1 translations by cells, jailhouse should implement
a emulated smmu driver that traps all smmu ste/translation updates. Only
these updates are trapped jailhouse should do policing on the updates
and make the updates in the proper locations.
Sounds frightening - complexity-wise, but also performance-wise. Do we have a
feeling for both, based on Linux experiences?
This driver is loosely based on the Linux kernel SMMU v3 driver.
Signed-off-by: Lokesh Vutla <[email protected]>
---
hypervisor/arch/arm64/Kbuild | 2 +-
hypervisor/arch/arm64/smmu-v3.c | 1017 ++++++++++++++++++++++++++
hypervisor/include/jailhouse/entry.h | 1 +
3 files changed, 1019 insertions(+), 1 deletion(-)
create mode 100644 hypervisor/arch/arm64/smmu-v3.c
How does this implementation roughly compare to
https://source.codeaurora.org/external/imx/imx-jailhouse/commit/?h=imx_4.14.78_1.0.0_ga&id=3ff00cf2e5a3c3197cbdeb668dfe90afa8f1076e?
The driver has a similar size, that's what I can see quickly, but I guess you
folks (including Peng) can explain quicker the differences, if there are
significant ones. Of course, the maintainer would prefer to have best of all
worlds in the end upstream :).
Thanks,
Jan
--
Siemens AG, Corporate Technology, CT RDA IOT SES-DE
Corporate Competence Center Embedded Linux
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