2016-09-15 12:08 GMT+08:00 Mika Penttilä <[email protected]>: > On 09/14/2016 10:58 AM, Wanpeng Li wrote: >> From: Wanpeng Li <[email protected]> >> >> 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
