a49dddbdb0
The ultracalls (ucalls for short) allow the Secure Virtual Machines (SVM)s and hypervisor to request services from the ultravisor such as accessing a register or memory region that can only be accessed when running in ultravisor-privileged mode. This patch adds the ucall_norets() ultravisor call handler. The specific service needed from an ucall is specified in register R3 (the first parameter to the ucall). Other parameters to the ucall, if any, are specified in registers R4 through R12. Return value of all ucalls is in register R3. Other output values from the ucall, if any, are returned in registers R4 through R12. Each ucall returns specific error codes, applicable in the context of the ucall. However, like with the PowerPC Architecture Platform Reference (PAPR), if no specific error code is defined for a particular situation, then the ucall will fallback to an erroneous parameter-position based code. i.e U_PARAMETER, U_P2, U_P3 etc depending on the ucall parameter that may have caused the error. Every host kernel (powernv) needs to be able to do ucalls in case it ends up being run in a machine with ultravisor enabled. Otherwise, the kernel may crash early in boot trying to access ultravisor resources, for instance, trying to set the partition table entry 0. Secure guests also need to be able to do ucalls and its kernel may not have CONFIG_PPC_POWERNV=y. For that reason, the ucall.S file is placed under arch/powerpc/kernel. If ultravisor is not enabled, the ucalls will be redirected to the hypervisor which must handle/fail the call. Thanks to inputs from Ram Pai and Michael Anderson. Signed-off-by: Claudio Carvalho <cclaudio@linux.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20190822034838.27876-3-cclaudio@linux.ibm.com |
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| Documentation | ||
| LICENSES | ||
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| 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 | ||
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.