On 15/06/18 00:32, Jiri Kosina wrote: > From: Jiri Kosina <jkos...@suse.cz> > > Xen PV domain is not by design affected by meltdown as it's enforcing > split CR3 itself. Let's not report such systems as "Vulnerable" in sysfs > (we're also already forcing PTI to off in X86_HYPER_XEN_PV cases) > > Reported-and-tested-by: Mike Latimer <mlati...@suse.com> > Signed-off-by: Jiri Kosina <jkos...@suse.cz> > --- > > I originally wanted to just not set X86_BUG_CPU_MELTDOWN in > cpu_set_bug_bits() in the first place, but that has two issues: > > - cpu_set_bug_bits() gets invoked from early_identify_cpu() before > init_hypervisor_platform() had a chance to run, and therefore the > hypervisor type check doesn't work there > > - it'd actually be inaccurate; the CPU *does* have the bug at the end > of the day (so it's properly kept being reported in cpuinfo), it's > "just a setup matter" that we don't need any addtional mitigation to > be applied by the kernel > > So let's not overcomplicate it. > > arch/x86/kernel/cpu/bugs.c | 4 ++++ > 1 file changed, 4 insertions(+) > > --- a/arch/x86/kernel/cpu/bugs.c > +++ b/arch/x86/kernel/cpu/bugs.c > @@ -26,6 +26,7 @@ > #include <asm/pgtable.h> > #include <asm/set_memory.h> > #include <asm/intel-family.h> > +#include <asm/hypervisor.h> > > static void __init spectre_v2_select_mitigation(void); > static void __init ssb_select_mitigation(void); > @@ -685,6 +686,9 @@ static ssize_t cpu_show_common(struct de > if (boot_cpu_has(X86_FEATURE_PTI)) > return sprintf(buf, "Mitigation: PTI\n"); > > + if (hypervisor_is_type(X86_HYPER_XEN_PV)) > + return sprintf(buf, "Not affected\n");
I don't like this. This is wrong for 32-bit guests and maybe wrong for 64-bit, too, in case the mitigation is disabled at hypervisor level. So the test should be done only for CONFIG_X86_64 and the returned string should be e.g. "Mitigation: XEN". Juergen
