Changes since RFC [Andy Lutomirski]: - Export new save_current_fsgs() API and call it before reading current->thread.fs/gsbase - New cpu_kernelmode_gs_base() API. - Some comments added. Some time ago Paolo suggested to take a look at probably unneeded expensive rdmsrs for FS/GS base MSR in vmx_save_host_state(). This is called on every vcpu run when we need to handle vmexit in userspace. vmx_save_host_state() is always called in a very well defined context (ioctl from userspace) so we may try to get the required values for FS/GS bases from in-kernel variables and avoid expensive rdmsrs. My debug shows we're shaving off 240 cpu cycles (E5-2603 v3). Vitaly Kuznetsov (3): x86/kvm/vmx: read MSR_FS_BASE from current->thread x86/kvm/vmx: read MSR_KERNEL_GS_BASE from current->thread x86/kvm/vmx: avoid expensive rdmsr for MSR_GS_BASE arch/x86/include/asm/processor.h | 8 ++++++++ arch/x86/kernel/cpu/common.c | 3 ++- arch/x86/kernel/process_64.c | 20 ++++++++++++++++++++ arch/x86/kvm/vmx.c | 9 ++++++--- 4 files changed, 36 insertions(+), 4 deletions(-) -- 2.14.3
