On 09/15/2016 07:25 AM, Wanpeng Li wrote: > 2016-09-15 12:08 GMT+08:00 Mika Penttilä <mika.pentt...@nextfour.com>: >> On 09/14/2016 10:58 AM, Wanpeng Li wrote: >>> From: Wanpeng Li <wanpeng...@hotmail.com> >>> >>> 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. >>> >> >> While at it, is the vmx flexpriotity stuff still valid code? >> AFAICS it gets enabled iff TPR shadow is on. flexpriority >> is on when : >> >> (flexpriority_enabled && lapic_in_kernel && cpu_has_vmx_tpr_shadow && >> cpu_has_vmx_virtualize_apic_accesses) >> >> But apic accesses to TPR mmio are not then trapped and TPR changes not >> reported because >> the “use TPR shadow” VM-execution control is 1. > > Please note the patch is for MSR-BASED TPR shadow w/o APICv, TPR > shadow can work correctly in other configurations. > > Regards, > Wanpeng Li >
Hi, Yes I see, this is slightly offtopic but while at flexpriority, how is it relevant in current kvm? In other words I see it as dead code, because it is enabled only when TPR shadow is enabled, and as such ineffective because TPR shadow disables the wmexits tpr reporting uses. Thanks, Mika
