mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/
synced 2026-10-14 05:55:17 +00:00
No description
- C 96.9%
- Assembly 0.9%
- Rust 0.6%
- Shell 0.6%
- Python 0.5%
- Other 0.3%
cad32d9d42
LoPAPR defines guest visible IOMMU with hypercalls to use it - H_PUT_TCE/etc. Implemented first on POWER7 where hypercalls would trap in the KVM in the real mode (with MMU off). The problem with the real mode is some memory is not available and some API usage crashed the host but enabling MMU was an expensive operation. The problems with the real mode handlers are: 1. Occasionally these cannot complete the request so the code is copied+modified to work in the virtual mode, very little is shared; 2. The real mode handlers have to be linked into vmlinux to work; 3. An exception in real mode immediately reboots the machine. If the small DMA window is used, the real mode handlers bring better performance. However since POWER8, there has always been a bigger DMA window which VMs use to map the entire VM memory to avoid calling H_PUT_TCE. Such 1:1 mapping happens once and uses H_PUT_TCE_INDIRECT (a bulk version of H_PUT_TCE) which virtual mode handler is even closer to its real mode version. On POWER9 hypercalls trap straight to the virtual mode so the real mode handlers never execute on POWER9 and later CPUs. So with the current use of the DMA windows and MMU improvements in POWER9 and later, there is no point in duplicating the code. The 32bit passed through devices may slow down but we do not have many of these in practice. For example, with this applied, a 1Gbit ethernet adapter still demostrates above 800Mbit/s of actual throughput. This removes the real mode handlers from KVM and related code from the powernv platform. This updates the list of implemented hcalls in KVM-HV as the realmode handlers are removed. This changes ABI - kvmppc_h_get_tce() moves to the KVM module and kvmppc_find_table() is static now. Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20220506053755.3820702-1-aik@ozlabs.ru |
History
|
|
|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.