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authorLinus Torvalds <torvalds@linux-foundation.org>2023-11-01 17:11:41 -1000
committerLinus Torvalds <torvalds@linux-foundation.org>2023-11-01 17:11:41 -1000
commitbabe393974de0351c0e6cca50f5f84edaf8d7fa1 (patch)
tree0893d62d555675d8bcfacc5d8e3965ef377791cd /Documentation/admin-guide/hw-vuln/mds.rst
parent7dc0e9c7dda66bd91eeada00d90033e3eb647fc3 (diff)
parentcf63348b4c45384d02126f86676d5afc75d661a7 (diff)
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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.rst34
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
-------------------------