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Some optional features of the Arm architecture add new system registers that are not present in the base architecture. Where these features are optional for the guest, the visibility of these registers may need to depend on some runtime configuration, such as a flag passed to KVM_ARM_VCPU_INIT. For example, ZCR_EL1 and ID_AA64ZFR0_EL1 need to be hidden if SVE is not enabled for the guest, even though these registers may be present in the hardware and visible to the host at EL2. Adding special-case checks all over the place for individual registers is going to get messy as the number of conditionally- visible registers grows. In order to help solve this problem, this patch adds a new sysreg method visibility() that can be used to hook in any needed runtime visibility checks. This method can currently return REG_HIDDEN_USER to inhibit enumeration and ioctl access to the register for userspace, and REG_HIDDEN_GUEST to inhibit runtime access by the guest using MSR/MRS. Wrappers are added to allow these flags to be conveniently queried. This approach allows a conditionally modified view of individual system registers such as the CPU ID registers, in addition to completely hiding register where appropriate. Signed-off-by: Dave Martin <Dave.Martin@arm.com> Tested-by: zhang.lei <zhang.lei@jp.fujitsu.com> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com> |
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| certs | ||
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| 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.