Switch MSR_IA32_FRED_RSP0 between host and guest in
vmx_prepare_switch_to_{host,guest}().MSR_IA32_FRED_RSP0 is used during ring 3 event delivery only, thus KVM, running on ring 0, can run safely with guest FRED RSP0, i.e., no need to switch between host/guest FRED RSP0 during VM entry and exit. KVM should switch to host FRED RSP0 before returning to user level, and switch to guest FRED RSP0 before entering guest mode. Signed-off-by: Xin Li <[email protected]> Tested-by: Shan Kang <[email protected]> --- Changes since v1: * Don't use guest_cpuid_has() in vmx_prepare_switch_to_{host,guest}(), which are called from IRQ-disabled context (Chao Gao). * Reset msr_guest_fred_rsp0 in __vmx_vcpu_reset() (Chao Gao). --- arch/x86/kvm/vmx/vmx.c | 17 +++++++++++++++++ arch/x86/kvm/vmx/vmx.h | 2 ++ 2 files changed, 19 insertions(+) diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index b7b772183ee4..264378c3b784 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -1337,6 +1337,16 @@ void vmx_prepare_switch_to_guest(struct kvm_vcpu *vcpu) } wrmsrl(MSR_KERNEL_GS_BASE, vmx->msr_guest_kernel_gs_base); + + if (guest_can_use(vcpu, X86_FEATURE_FRED)) { + /* + * MSR_IA32_FRED_RSP0 is top of task stack, which never changes. + * Thus it should be initialized only once. + */ + if (unlikely(vmx->msr_host_fred_rsp0 == 0)) + vmx->msr_host_fred_rsp0 = read_msr(MSR_IA32_FRED_RSP0); + wrmsrl(MSR_IA32_FRED_RSP0, vmx->msr_guest_fred_rsp0); + } #else savesegment(fs, fs_sel); savesegment(gs, gs_sel); @@ -1381,6 +1391,11 @@ static void vmx_prepare_switch_to_host(struct vcpu_vmx *vmx) invalidate_tss_limit(); #ifdef CONFIG_X86_64 wrmsrl(MSR_KERNEL_GS_BASE, vmx->msr_host_kernel_gs_base); + + if (guest_can_use(&vmx->vcpu, X86_FEATURE_FRED)) { + vmx->msr_guest_fred_rsp0 = read_msr(MSR_IA32_FRED_RSP0); + wrmsrl(MSR_IA32_FRED_RSP0, vmx->msr_host_fred_rsp0); + } #endif load_fixmap_gdt(raw_smp_processor_id()); vmx->guest_state_loaded = false; @@ -4889,6 +4904,8 @@ static void __vmx_vcpu_reset(struct kvm_vcpu *vcpu) #ifdef CONFIG_X86_64 if (kvm_cpu_cap_has(X86_FEATURE_FRED)) { + vmx->msr_guest_fred_rsp0 = 0; + vmcs_write64(GUEST_IA32_FRED_CONFIG, 0); vmcs_write64(GUEST_IA32_FRED_RSP1, 0); vmcs_write64(GUEST_IA32_FRED_RSP2, 0); diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h index 3ad52437f426..176ad39be406 100644 --- a/arch/x86/kvm/vmx/vmx.h +++ b/arch/x86/kvm/vmx/vmx.h @@ -278,6 +278,8 @@ struct vcpu_vmx { #ifdef CONFIG_X86_64 u64 msr_host_kernel_gs_base; u64 msr_guest_kernel_gs_base; + u64 msr_host_fred_rsp0; + u64 msr_guest_fred_rsp0; #endif u64 spec_ctrl; -- 2.43.0
