On 19/10/20 19:45, Graf (AWS), Alexander wrote: >> + * In principle it would be possible to trap x2apic ranges >> + * if !lapic_in_kernel. This however would be complicated >> + * because KVM_X86_SET_MSR_FILTER can be called before >> + * KVM_CREATE_IRQCHIP or KVM_ENABLE_CAP. >> + */ >> + for (i = 0; i < ARRAY_SIZE(filter.ranges); i++) >> + if (range_overlaps_x2apic(&filter.ranges[i])) >> + return -EINVAL; > > What if the default action of the filter is to "deny"? Then only an > MSR filter to allow access to x2apic MSRs would make the full > filtering logic adhere to the constraints, no? Right; or more precisely, that is handled by Sean's patch that he had posted earlier. This patch only makes it impossible to set up such a filter. (That said, this is a quick patch that I posted yesterday just before dinner. I'll send out the real deal with docs fixes and better commit message). Paolo > Also, this really deserves a comment in the API documentation :). > > In fact, I think a pure comment in documentation is enough. Just make > x2apic && filter on them "undefined behavior".
