Linux 7.2-rc6 Fixes Some AMD Zen 5 CPUs Being Mistakenly Identified As Zen 6

Today's batch of x86 fixes for the kernel ahead of the Linux 7.2-rc6 release later in the day addresses some AMD Zen 5 processors mistakenly being classified as Zen 6. A patch merged to the Linux kernel earlier this summer added more Zen 6 models to the kernel with the 0xd0 to 0xef IDs in Family 1Ah. Both Zen 5 and Zen 6 CPUs are part of Family 1Ah, but it turns out that 0xd0 to 0xd7 are actually reserved for Zen 5 and not Zen 6. So a new patch has come about to carve out 0xd0 to 0xd7 to being Zen 5 rather than Zen 6 while 0xc0 to 0xcf and 0xd8 to 0xef are the revised range, in addition to 0x50 to 0x5f and 0x80 to 0xaf all being IDs reserved for the upcoming Zen 6 processors. That part is part of the x86 fixes pull sent out a short time ago to the Linux kernel mailing list and should be merged ahead of the Linux 7.2-rc6 kernel release due out in approximately twelve hours. The only other x86 fixes patch for the week is adding the volatile qualifier and clobbers parameter for the kernel's x86 memcmp() implementation to prevent bugs with instruction reordering and optimizations. This fixes an issue raised last month over some unbootable VMs with Xen. To learn more about some upcoming AMD Zen 6 details, see the recent announcement from AMD Advancing AI with AMD EPYC 9006 Venice Announced & Looks Poised To Be A Grand Slam.