2016-09-14 17:40 GMT+08:00 Paolo Bonzini <pbonzini@xxxxxxxxxx>: > > > On 14/09/2016 09:58, Wanpeng Li wrote: >> From: Wanpeng Li <wanpeng.li@xxxxxxxxxxx> >> >> I observed that kvmvapic(to optimize flexpriority=N or AMD) is used >> to boost TPR access when testing kvm-unit-test/eventinj.flat tpr case >> on my haswell desktop (w/ flexpriority, w/o APICv). Commit (8d14695f9542 >> x86, apicv: add virtual x2apic support) disable virtual x2apic mode >> completely if w/o APICv, and the author also told me that windows guest >> can't enter into x2apic mode when he developed the APICv feature several >> years ago. However, it is not truth currently, Interrupt Remapping and >> vIOMMU is added to qemu and the developers from Intel test windows 8 can >> work in x2apic mode w/ Interrupt Remapping enabled recently. >> >> This patch enables TPR shadow for virtual x2apic mode to boost >> windows guest in x2apic mode even if w/o APICv. >> >> Can pass the kvm-unit-test. > > Ok, now I see what you meant; this actually makes sense. I don't expect > much speedup though, because Linux doesn't touch the TPR and Windows is > likely going to use the Hyper-V APIC MSRs when APICv is disabled. For > this reason I'm not sure if the patch is useful in practice. We should use more newer windows guests which have Hyper-V synthetic interrupt support, however, older windows guests can't get benefit. > > To test this patch, you have to run kvm-unit-tests with Hyper-V > synthetic interrupt enabled. Did you do this? qemu-system-x86_64 -enable-kvm -machine kernel_irqchip=split -cpu kvm64,hv_synic -device pc-testdev -device isa-debug-exit,iobase=0xf4,iosize=0x4 -vnc none -serial stdio -device pci-testdev -kernel x86/hyperv_synic.flat enabling apic paging enabled cr0 = 80010011 cr3 = 7fff000 cr4 = 20 enabling apic ncpus = 1 prepare test 0 -> 0 I run ./x86-run x86/hyperv_synic.flat against latest linus tree, it just stuck here. Regards, Wanpeng Li -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
