2016-09-15 8:07 GMT+08:00 Wanpeng Li <kernellwp@xxxxxxxxx>: > 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. Oops, I miss the "-device hyperv-testdev" parameter. And the patch passes the hyperv_sync.flat test case. 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
