Linux 5.8 Set to Optionally Flush the L1d Cache on Context Switch

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Linux 5.8 Set to Optionally Flush the L1d Cache on Context Switch

LINUX SECURITY --

The Linux kernel patches which have been spearheaded by Amazon AWS engineers to optionally flush the L1 recordsdata cache on each context swap have now been queued throughout the x86/mm department earlier than the upcoming Linux 5.eight kernel cycle.

This L1d cache flushing on context switches is being carried out in mild of the a call of CPU safety concerns which have attain to mild in newest instances and acknowledging there are almost certainly different but to be got here throughout vulnerabilities. Flushing the L1d cache on context switches helps fend off recordsdata from being snooped or leaked by technique of aspect channels.

This flushing does tackle CVE-2020-0550 for snoop-assisted L1 recordsdata sampling nonetheless the foremost emphasis seems to be on the “but to be got here throughout vulnerabilities.” However in flushing the L1 recordsdata cache so typically, there are huge efficiency implications and as such the documentation continues to examine with this performance as one factor for “paranoid” customers.

This opt-in mechanism desires to be enabled from individual-situation features by technique of prctl() and may probably maybe merely exhaust any CPU {hardware} mechanism for L1d flushing in any other case a machine fallback. Additional little print on this non-compulsory L1d flushing per context swap by technique of this earlier article.

The patches are queued throughout the x86/mm (reminiscence administration) department earlier than the Linux 5.eight kernel cycle anticipated to starting in early June after which liberate as secure almost certainly in August. Apart from this non-compulsory safety characteristic, there is perhaps worthy extra coming for Linux 5.8.

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