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5a8781607e
Currently, host_rsp is cached on a per-vCPU basis, i.e. it's stored in struct vcpu_vmx. In non-nested usage the caching is for all intents and purposes 100% effective, e.g. only the first VMLAUNCH needs to synchronize VMCS.HOST_RSP since the call stack to vmx_vcpu_run() is identical each and every time. But when running a nested guest, KVM must invalidate the cache when switching the current VMCS as it can't guarantee the new VMCS has the same HOST_RSP as the previous VMCS. In other words, the cache loses almost all of its efficacy when running a nested VM. Move host_rsp to struct vmcs_host_state, which is per-VMCS, so that it is cached on a per-VMCS basis and restores its 100% hit rate when nested VMs are in play. Note that the host_rsp cache for vmcs02 essentially "breaks" when nested early checks are enabled as nested_vmx_check_vmentry_hw() will see a different RSP at the time of its VM-Enter. While it's possible to avoid even that VMCS.HOST_RSP synchronization, e.g. by employing a dedicated VM-Exit stack, there is little motivation for doing so as the overhead of two VMWRITEs (~55 cycles) is dwarfed by the overhead of the extra VMX transition (600+ cycles) and is a proverbial drop in the ocean relative to the total cost of a nested transtion (10s of thousands of cycles). Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> Reviewed-by: Jim Mattson <jmattson@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> |
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| boot | ||
| configs | ||
| crypto | ||
| entry | ||
| events | ||
| hyperv | ||
| ia32 | ||
| include | ||
| kernel | ||
| kvm | ||
| lib | ||
| math-emu | ||
| mm | ||
| net | ||
| oprofile | ||
| pci | ||
| platform | ||
| power | ||
| purgatory | ||
| ras | ||
| realmode | ||
| tools | ||
| um | ||
| video | ||
| xen | ||
| .gitignore | ||
| Kbuild | ||
| Kconfig | ||
| Kconfig.cpu | ||
| Kconfig.debug | ||
| Makefile | ||
| Makefile_32.cpu | ||
| Makefile.um | ||