[Resurrecting post from the dead]
Marcelo Tosatti wrote: > Forcing clustered APIC mode works only on SMP, and there were high CPU > consumption on Windows SMP guests due to C3 state being reported (fixed > in kvm-30 something). > > So perhaps: > - Faking clustered APIC on SMP > - Faking C3 on UP > > And turning of the TSC bit (for 32-bit guests). > > Is the way to go? > > Avi, do you understand why C3 was causing the Windows SMP problems ? > > It's probably inb()ing on the port in a loop. It's not SMP causing the problems, but the ACPI HAL. I'll check this. > /* Common C-state entry for C2, C3, .. */ > static void acpi_cstate_enter(struct acpi_processor_cx *cstate) > { > if (cstate->space_id == ACPI_CSTATE_FFH) { > /* Call into architectural FFH based C-state */ > acpi_processor_ffh_cstate_enter(cstate); > } else { > int unused; > /* IO port based C-state */ > inb(cstate->address); > /* Dummy wait op - must do something useless after P_LVL2 read > because chipsets cannot guarantee that STPCLK# signal > gets asserted in time to freeze execution properly. */ > unused = inl(acpi_gbl_FADT.xpm_timer_block.address); > } > } > > Clearly that inb() won't actually idle under QEMU. So the question is, > if C3 stated is reported, that port read should be emulated... But how? > We can add now use the KVM_SET_MPSTATE ioctl to halt the vcpu if we see the port read. Since not all hosts support setting mpstate, the bios should only report C3 if the host supports it. -- error compiling committee.c: too many arguments to function ------------------------------------------------------------------------- This SF.net email is sponsored by the 2008 JavaOne(SM) Conference Don't miss this year's exciting event. There's still time to save $100. Use priority code J8TL2D2. http://ad.doubleclick.net/clk;198757673;13503038;p?http://java.sun.com/javaone _______________________________________________ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel