On Thu, 4 Jan 2018 12:07:21 +1300, Michael Cree wrote:
Now announced as Meltdown and Spectre.
According to this update <http://www.theregister.co.uk/2018/01/09/meltdown_spectre_slowdown/>, if your Intel CPU has the PCID feature, the most recent Linux kernels can take advantage of this to mitigate somewhat the performance hit from working around the vulnerabilities. How do you tell? Look in /proc/cpuinfo for the “flags” line. This will typically be pretty long, e.g. on my main machine (Core i7): flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx rdtscp lm constant_tsc arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc cpuid aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm pcid sse4_1 sse4_2 x2apic popcnt tsc_deadline_timer aes xsave avx f16c rdrand lahf_lm cpuid_fault epb tpr_shadow vnmi flexpriority ept vpid fsgsbase smep erms xsaveopt dtherm ida arat pln pts You have to hunt through that lot for the word “pcid”. I find it is also present on my older backup Core i5 machine as well. The full list of flags is defined in the Kernel source here <https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git/tree/arch/x86/include/asm/cpufeatures.h?id=refs/tags/v4.14>.