Daniel Sneddon 553a5c03e9 x86/speculation: Add force option to GDS mitigation ... The Gather Data Sampling (GDS) vulnerability allows malicious software to infer stale data previously stored in vector registers. This may include sensitive data such as cryptographic keys. GDS is mitigated in microcode, and systems with up-to-date microcode are protected by default. However, any affected system that is running with older microcode will still be vulnerable to GDS attacks. Since the gather instructions used by the attacker are part of the AVX2 and AVX512 extensions, disabling these extensions prevents gather instructions from being executed, thereby mitigating the system from GDS. Disabling AVX2 is sufficient, but we don't have the granularity to do this. The XCR0[2] disables AVX, with no option to just disable AVX2. Add a kernel parameter gather_data_sampling=force that will enable the microcode mitigation if available, otherwise it will disable AVX on affected systems. This option will be ignored if cmdline mitigations=off. This is a *big* hammer. It is known to break buggy userspace that uses incomplete, buggy AVX enumeration. Unfortunately, such userspace does exist in the wild: https://www.mail-archive.com/bug-coreutils@gnu.org/msg33046.html [ dhansen: add some more ominous warnings about disabling AVX ] Signed-off-by: Daniel Sneddon <daniel.sneddon@linux.intel.com> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>		2023-07-21 12:59:49 -07:00
..
core-scheduling.rst	uapi/linux/prctl: provide macro definitions for the PR_SCHED_CORE type argument	2021-09-29 13:00:05 +02:00
cross-thread-rsb.rst	Documentation/hw-vuln: Fix rST warning	2023-02-15 07:24:23 -05:00
gather_data_sampling.rst	x86/speculation: Add force option to GDS mitigation	2023-07-21 12:59:49 -07:00
index.rst	x86/speculation: Add Gather Data Sampling mitigation	2023-07-19 16:45:37 -07:00
l1d_flush.rst	Documentation: Add L1D flushing Documentation	2021-07-28 11:42:25 +02:00
l1tf.rst	docs: add IRQ documentation at the core-api book	2020-05-15 12:00:56 -06:00
mds.rst	docs: move x86 documentation into Documentation/arch/	2023-03-30 12:58:51 -06:00
multihit.rst	x86/bugs/multihit: Fix mitigation reporting when VMX is not in use	2020-08-07 01:32:00 +02:00
processor_mmio_stale_data.rst	x86/bugs: Add "unknown" reporting for MMIO Stale Data	2022-08-18 15:35:22 +02:00
special-register-buffer-data-sampling.rst	docs: admin-guide: hw-vuln: avoid using ReST :doc:foo markup	2021-06-17 13:24:36 -06:00
spectre.rst	Documentation/hw-vuln: Document the interaction between IBRS and STIBP	2023-02-27 19:02:47 +01:00
tsx_async_abort.rst	docs: move x86 documentation into Documentation/arch/	2023-03-30 12:58:51 -06:00