Linux 6.15 Set To Include Better Handling For Intel P Or E Core Only Mitigations
A set of patches from Intel for utilizing the CPU type for CPU matching as part of the x86 mitigation handling is likely to be part of the upcoming Linux 6.15 kernel. These patches are intended for helping with CPU security mitigations on Intel Core hybrid processors where there are security vulnerabilities affecting only P cores or only E cores but not both sets of CPU cores present in the system.
For a number of months Intel engineers have been working to properly handle the CPU hybrid topology for determining vulnerabilities/mitigations rather than blanket applying mitigations (or not) across both sets of CPU cores even if only the P or E cores are vulnerable.
Intel's motivation for this is initially around the Register File Data Sampling (RFDS) vulnerability where only the E cores on Alder Lake and Raptor Lake are susceptible to the issue. The P cores are not and thus the patch series will properly handle this case of applying to the specific CPU type that's vulnerable. So now with Linux 6.15+ the P cores on Raptor Lake and Alder Lake CPUs would be properly excluded. The patches add in the proper infrastructure and then this RFDS handling is the only use case for the moment.
These patches were queued up into tip/tip.git's x86/cpu branch ahead of the Linux 6.15 merge window opening later in March. With the patches part of the x86/cpu TIP branch, they are expected to be submitted and merged for Linux 6.15 barring any last minute issues or objections from being raised.
For a number of months Intel engineers have been working to properly handle the CPU hybrid topology for determining vulnerabilities/mitigations rather than blanket applying mitigations (or not) across both sets of CPU cores even if only the P or E cores are vulnerable.
Intel's motivation for this is initially around the Register File Data Sampling (RFDS) vulnerability where only the E cores on Alder Lake and Raptor Lake are susceptible to the issue. The P cores are not and thus the patch series will properly handle this case of applying to the specific CPU type that's vulnerable. So now with Linux 6.15+ the P cores on Raptor Lake and Alder Lake CPUs would be properly excluded. The patches add in the proper infrastructure and then this RFDS handling is the only use case for the moment.
These patches were queued up into tip/tip.git's x86/cpu branch ahead of the Linux 6.15 merge window opening later in March. With the patches part of the x86/cpu TIP branch, they are expected to be submitted and merged for Linux 6.15 barring any last minute issues or objections from being raised.