On 04/11/2015 21:08, Laszlo Ersek wrote: > On 11/04/15 17:55, Kinney, Michael D wrote: >> Laszlo, >> >> BaseXApicX2ApicLib is intended to be used by platforms that support more >> >=256 CPUs. >> >> If the current system configuration is < 256 CPUs, then the platform will >> typically stay in APIC mode. If >= 256 CPUs are detected, then X2 APIC mode >> can be enabled using the following API. >> >> VOID >> EFIAPI >> SetApicMode ( >> IN UINTN ApicMode >> ) >> >> So just adding BaseXApicX2ApicLib to the DSC does not enable X2 APIC mode. >> You have to add logic to enable X2 APIC mode. >> >> I see that QEMU is limited to 255 VCPUs, so the use of BaseXApicLib makes >> sense. Are OVMF configurations supported with >= 256 VCPUs? > > I don't think so, but 64-bit Linux guest kernels enable x2apic mode > anyway, apparently regardless of the VCPU count and topology.
Yup, x2apic-style accesses (via MSRs) are faster because you do not have to walk the page tables. Paolo _______________________________________________ edk2-devel mailing list edk2-devel@lists.01.org https://lists.01.org/mailman/listinfo/edk2-devel
