[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH v3 0/4] Expose HW APIC virtualization support to HVM guests
Version 3: * Removed sysctl for querying hypervisor leaf from libxc, replaced it with prefixed CPUID instruction * Limited ability change hypervisor leaves to 0x40000000 * Fixed IS_HYPERVISOR_LEAF macro Version 2: * Added ability to specify hypervisor CPUID leaves in config file (this requires new sysctl) * Use 2 bits to indicate what is supported --- one for APIC memory access and the other for x2APIC. Still not sure whether virtual interrupt delivery should be exposed as well. HVM guests running on HW that supports HW APIC virtualization features (APIC-register virtualization, virtual interrupt delivery, etc) may want to use APIC instead of hvm_pirqs. Since we are not guaranteed to have these features on VMX (for example, there is a boot option to turn it off) and there is no such support on SVM we need to make the guest aware that its APIC accesses may not be so bad. CPUID seems to be a good way to provide this info to the guest. Having a guest switch to APIC shows fairly good impact on number of VMEXITs. For example, with a pass-through NIC, netperf sees almost half as many. Here are results for 'xentrace -e 0x00083fff -c 2 -D -T 2' (The guest here essentially turned off XENFEAT_hvm_pirqs but we may want to use APIC for MSI interrupts only and leave pirqs for gsi). [root@ovs105 virt]# cat orig |xentrace_format ~/xen/tools/xentrace/formats | awk '{print $5}' | sort | uniq -c 94 cpu_change 13944 HLT 26341 INJ_VIRQ 12054 INTR 30784 INTR_WINDOW 10126 TRAP 124783 VMENTRY 124782 VMEXIT 59217 VMMCALL 35 wrap_buffer [root@ovs105 virt]# cat apicv |xentrace_format ~/xen/tools/xentrace/formats | awk '{print $5}' | sort | uniq -c 49 cpu_change 16157 HLT 31 INJ_VIRQ 10652 INTR 38 INTR_WINDOW 10 NPF 10286 TRAP 71269 VMENTRY 71269 VMEXIT 34129 VMMCALL 15 wrap_buffer The difference is even larger when the guest is busy. These results are in line with what has been reported for KVM. For example http://events.linuxfoundation.org/sites/events/files/cojp13_natapov.pdf http://www.linuxplumbersconf.org/2012/wp-content/uploads/2012/09/2012-lpc-virt-intel-vt-feat-nakajima.pdf I am also not sure whether (cpu_has_vmx_apic_reg_virt & cpu_has_vmx_virtualize_x2apic_mode) is sufficient to declare full HW APIC support to a guest. The tests show ~95K VMEXITs when virtual interrupt delivery and posted interrupts are turned off so there appears to still be some benefit. I suppose we can use another CPUID bit for these two (although I am not particularly eager to do this). Boris Ostrovsky (4): xen/libxc: Allow changes to hypervisor CPUID leaf from config file x86/hvm: Revert 80ecb40362365ba77e68fc609de8bd3b7208ae19 x86/hvm: Add HVM-specific hypervisor CPUID leaf x86/hvm: Indicate avaliability of HW support of APIC virtualization to HVM guests tools/libxc/xc_cpuid_x86.c | 31 ++++++++++++++++++++++++++----- xen/arch/x86/domain.c | 19 ++++++++++++++++--- xen/arch/x86/hvm/hvm.c | 16 ++++++++++++++++ xen/arch/x86/hvm/vmx/vmx.c | 12 ++++++++++++ xen/arch/x86/traps.c | 18 +++++++++--------- xen/include/asm-x86/domain.h | 7 +++++++ xen/include/asm-x86/hvm/hvm.h | 7 +++++++ xen/include/public/arch-x86/cpuid.h | 10 ++++++++++ 8 files changed, 103 insertions(+), 17 deletions(-) -- 1.7.10.4 _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
|
Lists.xenproject.org is hosted with RackSpace, monitoring our |