| From: D. Hugh Redelmeier via talk <talk@gtalug.org> | | | >And then there is the Spectre bug also lurking ... | | | | Microsoft has stopped, temporarily, updating AMD due to poor documentation. | | | | https://www.theverge.com/2018/1/9/16867068/microsoft-meltdown-spectre-security-updates-amd-pcs-issues> | | Thanks for this reference. I hadn't seen that. | | Microsoft isn't too clear about their finger-pointing (that doesn't | mean that they are wrong). This notice isn't very clear: | <https://support.microsoft.com/en-us/help/4073707/windows-os-security-update-block-for-some-amd-based-devices> | | - it would be really handy if they explained what "some" means. Which | AMD-based devices are currently blocked | | - this run-on sentence might not mean what it is supposed to | | After investigating, Microsoft has determined that some AMD | chipsets do not conform to the documentation previously | provided to Microsoft to develop the Windows operating system | mitigations to protect against the chipset vulnerabilities | known as Spectre and Meltdown. | | - Spectre and Meltdown are different. The fixes are different. | Preventing installation of the fixes for both is probably a mistake. | | To be honest, I don't understand why these mitigations involve a | chipset at all. The current best guess is that Microsoft forgot that early x86-64 machines did not have a CMPXCHG16B instruction. So patch KB4056897 used it and crashed. I base this on things referenced in the last paragraph of <https://arstechnica.com/gadgets/2018/01/bad-docs-and-blue-screens-make-microsoft-suspend-spectre-patch-for-amd-machines/> Alternatively, the problem MIGHT be that the processor has the instruction but that the chipset doesn't implement its part (lock?). I have read that Win8.1 and later require CMPXCHG16B so these problems are likely only showing up in Win 7 and Win 8 or perhaps even older systems. Is see the flag "cx16" in /proc/cpuid. I bet that tells me my CPU has the feature. <https://superuser.com/questions/187254/how-prevalent-are-old-x64-processors-lacking-the-cmpxchg16b-instruction>