AMD processors are not subject to the types of attacks that the kernel page table isolation feature protects against. The AMD microarchitecture

does not allow memory references, including speculative references, that access higher privileged data when running in a lesser privileged mode

when that access would result in a page fault. Disable page table isolation by default on AMD processors by not setting the X86_BUG_CPU_INSECURE feature, which controls whether X86_FEATURE_PTI

is set.

Intel's CPUs [can] speculatively execute code potentially without performing security checks".

On Monday a Blogpost started circulating regarding an " embargoed security bug ", which has forced both extreme redesigns of both Linux and Windows Kernels to address the issue. This bug is said to exclusively affect Intel processors, allowing normal programs to discern the contents of protected kernel memory. Kernel memory is hidden for a reason, though at this time exact information about this exploit is unknown.Right now, it looks like this issue is unfixable using microcode updates, which means that a software solution is required. Right now, it seems like the fix will require a separation of kernel memory from user processes, requiring time inefficient address space shifting that is expected to lower the performance of Intel-based systems.The effects of these major software updates are unknown, though early estimates have placed the performance hit at between 5 and 30 percent , though newer Intel processors do have features that are said to reduce the slowdown. If these reports are true, Intel is in for a lot of trouble. The performance drop will depend on how much tasks depend on kernel access which is where the slowdown will occur.One thing to note here is that this issue was originally reported as a " security bug impacting apparently all contemporary CPU architectures ", though now it seems like AMD architectures are not affected by this problem.Over Christmas, an email was sent to the Linux kernel mailing list , stating that that "AMD processors are not subject to the types of attacks that the kernel page table isolation feature protects against". This email was sent by Thomas Lendacky, a software engineer at AMD that specialises in Linux kernel development. Below is the full email.As The Register points out, this email implies that the problem is exclusive to Intel processors and suggests that "Both Amazon's web services and Microsoft's Azure cloud are expected to undergo security updates and maintenance within the next two week. These updates are to expected implement security fixes that will address this issue. At this time it is unknown when fixes will be available on consumer-grade operating systems.