This patch fixes two corner cases in nested (L2) handling of TSC-related issues:
1. Somewhat suprisingly, according to the Intel spec, if L1 allows WRMSR to the TSC MSR without an exit, then this should set L1's TSC value itself - not offset by vmcs12.TSC_OFFSET (like was wrongly done in the previous code). 2. Allow L1 to disable the TSC_OFFSETING control, and then correctly ignore the vmcs12.TSC_OFFSET. Signed-off-by: Nadav Har'El <[email protected]> --- arch/x86/kvm/vmx.c | 31 +++++++++++++++++++++---------- 1 file changed, 21 insertions(+), 10 deletions(-) --- .before/arch/x86/kvm/vmx.c 2011-08-02 15:51:02.000000000 +0300 +++ .after/arch/x86/kvm/vmx.c 2011-08-02 15:51:02.000000000 +0300 @@ -1777,15 +1777,23 @@ static void vmx_set_tsc_khz(struct kvm_v */ static void vmx_write_tsc_offset(struct kvm_vcpu *vcpu, u64 offset) { - vmcs_write64(TSC_OFFSET, offset); - if (is_guest_mode(vcpu)) + if (is_guest_mode(vcpu)) { /* - * We're here if L1 chose not to trap the TSC MSR. Since - * prepare_vmcs12() does not copy tsc_offset, we need to also - * set the vmcs12 field here. + * We're here if L1 chose not to trap WRMSR to TSC. According + * to the spec, this should set L1's TSC; The offset that L1 + * set for L2 remains unchanged, and still needs to be added + * to the newly set TSC to get L2's TSC. */ - get_vmcs12(vcpu)->tsc_offset = offset - - to_vmx(vcpu)->nested.vmcs01_tsc_offset; + struct vmcs12 *vmcs12; + to_vmx(vcpu)->nested.vmcs01_tsc_offset = offset; + /* recalculate vmcs02.TSC_OFFSET: */ + vmcs12 = get_vmcs12(vcpu); + vmcs_write64(TSC_OFFSET, offset + + (nested_cpu_has(vmcs12, CPU_BASED_USE_TSC_OFFSETING) ? + vmcs12->tsc_offset : 0)); + } else { + vmcs_write64(TSC_OFFSET, offset); + } } static void vmx_adjust_tsc_offset(struct kvm_vcpu *vcpu, s64 adjustment) @@ -6529,8 +6537,11 @@ static void prepare_vmcs02(struct kvm_vc set_cr4_guest_host_mask(vmx); - vmcs_write64(TSC_OFFSET, - vmx->nested.vmcs01_tsc_offset + vmcs12->tsc_offset); + if (vmcs12->cpu_based_vm_exec_control & CPU_BASED_USE_TSC_OFFSETING) + vmcs_write64(TSC_OFFSET, + vmx->nested.vmcs01_tsc_offset + vmcs12->tsc_offset); + else + vmcs_write64(TSC_OFFSET, vmx->nested.vmcs01_tsc_offset); if (enable_vpid) { /* @@ -6937,7 +6948,7 @@ static void nested_vmx_vmexit(struct kvm load_vmcs12_host_state(vcpu, vmcs12); - /* Update TSC_OFFSET if vmx_adjust_tsc_offset() was used while L2 ran */ + /* Update TSC_OFFSET if TSC was changed while L2 ran */ vmcs_write64(TSC_OFFSET, vmx->nested.vmcs01_tsc_offset); /* This is needed for same reason as it was needed in prepare_vmcs02 */ -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
