From: "Xin Li (Intel)" <[email protected]> Save guest FRED RSP0 in vmx_prepare_switch_to_host() and restore it in vmx_prepare_switch_to_guest() because MSR_IA32_FRED_RSP0 is passed through to the guest, thus is volatile/unknown.
Note, host FRED RSP0 is restored in arch_exit_to_user_mode_prepare(), regardless of whether it is modified in KVM. Signed-off-by: Xin Li (Intel) <[email protected]> Signed-off-by: Sohil Mehta <[email protected]> Reviewed-by: Chao Gao <[email protected]> Reviewed-by: Binbin Wu <[email protected]> --- v10: - No change Note, an equivalent TDX side implementation is missing. No TDX module with FRED support exists yet so this would be an issue for future platforms. A generic discussion regarding this is ongoing at: https://lore.kernel.org/kvm/[email protected]/ --- arch/x86/kvm/vmx/vmx.c | 13 +++++++++++++ arch/x86/kvm/vmx/vmx.h | 1 + 2 files changed, 14 insertions(+) diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 09bbbc680aa7..b6b73ab9cfb7 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -1395,6 +1395,9 @@ void vmx_prepare_switch_to_guest(struct kvm_vcpu *vcpu) } wrmsrq(MSR_KERNEL_GS_BASE, vmx->msr_guest_kernel_gs_base); + + if (guest_cpu_cap_has(vcpu, X86_FEATURE_FRED)) + wrmsrns(MSR_IA32_FRED_RSP0, vmx->msr_guest_fred_rsp0); #else savesegment(fs, fs_sel); savesegment(gs, gs_sel); @@ -1439,6 +1442,16 @@ static void vmx_prepare_switch_to_host(struct vcpu_vmx *vmx) invalidate_tss_limit(); #ifdef CONFIG_X86_64 wrmsrq(MSR_KERNEL_GS_BASE, vmx->vt.msr_host_kernel_gs_base); + + if (guest_cpu_cap_has(&vmx->vcpu, X86_FEATURE_FRED)) { + vmx->msr_guest_fred_rsp0 = read_msr(MSR_IA32_FRED_RSP0); + /* + * Synchronize the current value in hardware to the kernel's + * local cache. The desired host RSP0 will be set when the + * CPU exits to userspace (RSP0 is a per-task value). + */ + fred_sync_rsp0(vmx->msr_guest_fred_rsp0); + } #endif load_fixmap_gdt(raw_smp_processor_id()); vmx->vt.guest_state_loaded = false; diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h index 7a22e1b1a273..14fd3f57d5c1 100644 --- a/arch/x86/kvm/vmx/vmx.h +++ b/arch/x86/kvm/vmx/vmx.h @@ -222,6 +222,7 @@ struct vcpu_vmx { bool guest_uret_msrs_loaded; #ifdef CONFIG_X86_64 u64 msr_guest_kernel_gs_base; + u64 msr_guest_fred_rsp0; #endif u64 spec_ctrl; -- 2.43.0
