On Fri, 2018-01-12 at 22:40 +0100, Vincent Lefevre wrote: > On 2018-01-12 21:21:06 +0000, Nick wrote: > > It might have aged out of the buffer that dmesg reports on. > > No, there's the beginning of the dmesg output: > > [ 0.000000] Linux version 4.9.0-5-amd64 ([email protected]) > (gcc version 6.3.0 20170516 (Debian 6.3.0-18) ) #1 SMP Debian 4.9.65-3+deb9u2 > (2018-01-04) > > But I think I've found the reason: > > In arch/x86/mm/kaiser.c: > > void __init kaiser_check_boottime_disable(void) > { > [...] > if (boot_cpu_has(X86_FEATURE_XENPV)) > goto silent_disable; > [...] > disable: > pr_info("disabled\n"); > > silent_disable: > kaiser_enabled = 0; > setup_clear_cpu_cap(X86_FEATURE_KAISER); > } > > I must be in the "silent_disable" case (this is a Xen guest). > > It's unfortunate that no-one mentions this case!
Hmm. I have a system running under Xen and get the 'page tables isolation: enabled' message. Here's what I hope are relevant parts from dmesg output... [ 0.000000] Linux version 4.9.0-5-amd64 ([email protected]) (gcc version 6.3.0 20170 516 (Debian 6.3.0-18) ) #1 SMP Debian 4.9.65-3+deb9u2 (2018-01-04) ... [ 0.000000] DMI: Xen HVM domU, BIOS 4.8.1-pre-memset3 06/07/2017 [ 0.000000] Hypervisor detected: Xen [ 0.000000] Xen version 4.8. ... [ 0.000000] Booting paravirtualized kernel on Xen HVM ... [ 0.000000] Kernel/User page tables isolation: enabled -- Tixy
