mirror of
https://github.com/AuxXxilium/linux_dsm_epyc7002.git
synced 2025-02-23 17:56:28 +07:00
4dc9680428
commit f71a53d1180d5ecc346f0c6a23191d837fe2871b upstream. Restore CR4.LA57 to the mmu_role to fix an amusing edge case with nested virtualization. When KVM (L0) is using TDP, CR4.LA57 is not reflected in mmu_role.base.level because that tracks the shadow root level, i.e. TDP level. Normally, this is not an issue because LA57 can't be toggled while long mode is active, i.e. the guest has to first disable paging, then toggle LA57, then re-enable paging, thus ensuring an MMU reinitialization. But if L1 is crafty, it can load a new CR4 on VM-Exit and toggle LA57 without having to bounce through an unpaged section. L1 can also load a new CR3 on exit, i.e. it doesn't even need to play crazy paging games, a single entry PML5 is sufficient. Such shenanigans are only problematic if L0 and L1 use TDP, otherwise L1 and L2 share an MMU that gets reinitialized on nested VM-Enter/VM-Exit due to mmu_role.base.guest_mode. Note, in the L2 case with nested TDP, even though L1 can switch between L2s with different LA57 settings, thus bypassing the paging requirement, in that case KVM's nested_mmu will track LA57 in base.level. This reverts commit |
||
|---|---|---|
| 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.