From 74a497fae754bd970ad0573c26d0a3c5e784fa0c Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Wed, 20 Dec 2017 13:55:39 +0100 Subject: KVM: nVMX: track dirty state of non-shadowed VMCS fields MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit VMCS12 fields that are not handled through shadow VMCS are rarely written, and thus they are also almost constant in the vmcs02. We can thus optimize prepare_vmcs02 by skipping all the work for non-shadowed fields in the common case. This patch introduces the (pretty simple) tracking infrastructure; the next patches will move work to prepare_vmcs02_full and save a few hundred clock cycles per VMRESUME on a Haswell Xeon E5 system: before after cpuid 14159 13869 vmcall 15290 14951 inl_from_kernel 17703 17447 outl_to_kernel 16011 14692 self_ipi_sti_nop 16763 15825 self_ipi_tpr_sti_nop 17341 15935 wr_tsc_adjust_msr 14510 14264 rd_tsc_adjust_msr 15018 14311 mmio-wildcard-eventfd:pci-mem 16381 14947 mmio-datamatch-eventfd:pci-mem 18620 17858 portio-wildcard-eventfd:pci-io 15121 14769 portio-datamatch-eventfd:pci-io 15761 14831 (average savings 748, stdev 460). Signed-off-by: Paolo Bonzini Signed-off-by: Radim Krčmář --- arch/x86/kvm/vmx_shadow_fields.h | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'arch/x86/kvm/vmx_shadow_fields.h') diff --git a/arch/x86/kvm/vmx_shadow_fields.h b/arch/x86/kvm/vmx_shadow_fields.h index 31d7a15338ac..cd0c75f6d037 100644 --- a/arch/x86/kvm/vmx_shadow_fields.h +++ b/arch/x86/kvm/vmx_shadow_fields.h @@ -17,6 +17,12 @@ * (e.g. force a sync if VM_INSTRUCTION_ERROR is modified * by nested_vmx_failValid) * + * When adding or removing fields here, note that shadowed + * fields must always be synced by prepare_vmcs02, not just + * prepare_vmcs02_full. + */ + +/* * Keeping the fields ordered by size is an attempt at improving * branch prediction in vmcs_read_any and vmcs_write_any. */ -- cgit v1.2.3