Merged this weekend ahead of the Linux 6.18-rc4 test kernel release due out later today is the “x86/fixes” for the week. There are a few notable changes on the x86 (x86_64) side of the kernel this week for Linux 6.18.
First up, more AMD Zen 6 CPU model IDs are now recognized by the kernel as part of enabling these next-generation processors for Linux. As covered when the kernel patch was first posted, AMD is now adding additional Zen 6 model IDs to the Family 1Ah. The range of recognized Zen 6 model IDs is now expanded by 16 to make way in advance for more potential Zen 6 based products.
Also on the AMD side is disabling RDSEED use on select Zen 5 CPUs with older microcode where there’s that previously talked about RDSEED bug. Reported a few weeks back was a Zen 5 architectural issue with RDSEED usage for RNG seeding. This week AMD acknowledged the RDSEED issue and has a microcode/AGESA fix coming with the updated AMD EPYC 9005 microcode already shipping while software updates for other hardware will be out in the coming weeks.
Linux 6.18-rc4 is disabling RDSEED on affected Zen 5 CPUs with microcode version prior to that fix being applied. Separately, the x86/fixes pull also has a fix for AMD FPU XFD state synchronization on signal delivery.
The pull also has a fix for kernel builds with CONFIG_CFI=y and CONFIG_LTO_CLANG_FULL=y to avoid build failures.
More details on this week’s x86/fixes via this pull request with those patches having now been merged to Linux Git ahead of Linux 6.18-rc4 coming out later today.
