[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [RFC Patch v4 4/8] hvmloader: boot cpu through broadcast
On Fri, Feb 23, 2018 at 04:42:10PM +0000, Roger Pau Monné wrote: >On Wed, Dec 06, 2017 at 03:50:10PM +0800, Chao Gao wrote: >> Intel SDM Extended XAPIC (X2APIC) -> "Initialization by System Software" >> has the following description: >> >> "The ACPI interfaces for the x2APIC are described in Section 5.2, “ACPI >> System >> Description Tables,” of the Advanced Configuration and Power Interface >> Specification, Revision 4.0a (http://www.acpi.info/spec.htm). The default >> behavior for BIOS is to pass the control to the operating system with the >> local x2APICs in xAPIC mode if all APIC IDs reported by CPUID.0BH:EDX are >> less >> than 255, and in x2APIC mode if there are any logical processor reporting an >> APIC ID of 255 or greater." >> >> In this patch, hvmloader enables x2apic mode for all vcpus if there are cpus >> with APIC ID > 255. To wake up processors whose APIC ID is greater than 255, >> the SIPI is broadcasted to all APs. It is the way how Seabios wakes up APs. >> APs may compete for the stack, thus a lock is introduced to protect the >> stack. > >Hm, how are we going to deal with this on PVH? hvmloader doesn't run >for PVH guests, hence it seems like switching to x2APIC mode should be >done somewhere else that shared between HVM and PVH. > >Maybe the hypercall that sets the number of vCPUs should change the >APIC mode? Yes. A flag can be passed when setting the maximum number of vCPUs. Xen will switch all local APICs to x2APIC mode or xAPIC mode according to the flag. Thanks Chao _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxxx https://lists.xenproject.org/mailman/listinfo/xen-devel
|
Lists.xenproject.org is hosted with RackSpace, monitoring our |