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author | Linus Torvalds <torvalds@linux-foundation.org> | 2023-11-01 17:11:41 -1000 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2023-11-01 17:11:41 -1000 |
commit | babe393974de0351c0e6cca50f5f84edaf8d7fa1 (patch) | |
tree | 0893d62d555675d8bcfacc5d8e3965ef377791cd /Documentation/admin-guide/hw-vuln/mds.rst | |
parent | 7dc0e9c7dda66bd91eeada00d90033e3eb647fc3 (diff) | |
parent | cf63348b4c45384d02126f86676d5afc75d661a7 (diff) | |
download | linux-stable-babe393974de0351c0e6cca50f5f84edaf8d7fa1.tar.gz linux-stable-babe393974de0351c0e6cca50f5f84edaf8d7fa1.tar.bz2 linux-stable-babe393974de0351c0e6cca50f5f84edaf8d7fa1.zip |
Merge tag 'docs-6.7' of git://git.lwn.net/linux
Pull documentation updates from Jonathan Corbet:
"The number of commits for documentation is not huge this time around,
but there are some significant changes nonetheless:
- Some more Spanish-language and Chinese translations
- The much-discussed documentation of the confidential-computing
threat model
- Powerpc and RISCV documentation move under Documentation/arch -
these complete this particular bit of documentation churn
- A large traditional-Chinese documentation update
- A new document on backporting and conflict resolution
- Some kernel-doc and Sphinx fixes
Plus the usual smattering of smaller updates and typo fixes"
* tag 'docs-6.7' of git://git.lwn.net/linux: (40 commits)
scripts/kernel-doc: Fix the regex for matching -Werror flag
docs: backporting: address feedback
Documentation: driver-api: pps: Update PPS generator documentation
speakup: Document USB support
doc: blk-ioprio: Bring the doc in line with the implementation
docs: usb: fix reference to nonexistent file in UVC Gadget
docs: doc-guide: mention 'make refcheckdocs'
Documentation: fix typo in dynamic-debug howto
scripts/kernel-doc: match -Werror flag strictly
Documentation/sphinx: Remove the repeated word "the" in comments.
docs: sparse: add SPDX-License-Identifier
docs/zh_CN: Add subsystem-apis Chinese translation
docs/zh_TW: update contents for zh_TW
docs: submitting-patches: encourage direct notifications to commenters
docs: add backporting and conflict resolution document
docs: move riscv under arch
docs: update link to powerpc/vmemmap_dedup.rst
mm/memory-hotplug: fix typo in documentation
docs: move powerpc under arch
PCI: Update the devres documentation regarding to pcim_*()
...
Diffstat (limited to 'Documentation/admin-guide/hw-vuln/mds.rst')
-rw-r--r-- | Documentation/admin-guide/hw-vuln/mds.rst | 34 |
1 files changed, 13 insertions, 21 deletions
diff --git a/Documentation/admin-guide/hw-vuln/mds.rst b/Documentation/admin-guide/hw-vuln/mds.rst index 48ca0bd85604..48c7b0b72aed 100644 --- a/Documentation/admin-guide/hw-vuln/mds.rst +++ b/Documentation/admin-guide/hw-vuln/mds.rst @@ -102,9 +102,19 @@ The possible values in this file are: * - 'Vulnerable' - The processor is vulnerable, but no mitigation enabled * - 'Vulnerable: Clear CPU buffers attempted, no microcode' - - The processor is vulnerable but microcode is not updated. - - The mitigation is enabled on a best effort basis. See :ref:`vmwerv` + - The processor is vulnerable but microcode is not updated. The + mitigation is enabled on a best effort basis. + + If the processor is vulnerable but the availability of the microcode + based mitigation mechanism is not advertised via CPUID, the kernel + selects a best effort mitigation mode. This mode invokes the mitigation + instructions without a guarantee that they clear the CPU buffers. + + This is done to address virtualization scenarios where the host has the + microcode update applied, but the hypervisor is not yet updated to + expose the CPUID to the guest. If the host has updated microcode the + protection takes effect; otherwise a few CPU cycles are wasted + pointlessly. * - 'Mitigation: Clear CPU buffers' - The processor is vulnerable and the CPU buffer clearing mitigation is enabled. @@ -119,24 +129,6 @@ to the above information: 'SMT Host state unknown' Kernel runs in a VM, Host SMT state unknown ======================== ============================================ -.. _vmwerv: - -Best effort mitigation mode -^^^^^^^^^^^^^^^^^^^^^^^^^^^ - - If the processor is vulnerable, but the availability of the microcode based - mitigation mechanism is not advertised via CPUID the kernel selects a best - effort mitigation mode. This mode invokes the mitigation instructions - without a guarantee that they clear the CPU buffers. - - This is done to address virtualization scenarios where the host has the - microcode update applied, but the hypervisor is not yet updated to expose - the CPUID to the guest. If the host has updated microcode the protection - takes effect otherwise a few cpu cycles are wasted pointlessly. - - The state in the mds sysfs file reflects this situation accordingly. - - Mitigation mechanism ------------------------- |