Arthur Chunqi Li wrote on 2013-09-04:
> This patch contains the following two changes:
> 1. Fix the bug in nested preemption timer support. If vmexit L2->L0 with some
> reasons not emulated by L1, preemption timer value should be save in such
> exits.
> 2. Add support of "Save VMX-preemption timer value" VM-Exit controls to
> nVMX.
>
> With this patch, nested VMX preemption timer features are fully supported.
>
> Signed-off-by: Arthur Chunqi Li <yzt356@xxxxxxxxx>
> ---
> This series depends on queue.
>
> arch/x86/include/uapi/asm/msr-index.h | 1 +
> arch/x86/kvm/vmx.c | 51
> ++++++++++++++++++++++++++++++---
> 2 files changed, 48 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/include/uapi/asm/msr-index.h
> b/arch/x86/include/uapi/asm/msr-index.h
> index bb04650..b93e09a 100644
> --- a/arch/x86/include/uapi/asm/msr-index.h
> +++ b/arch/x86/include/uapi/asm/msr-index.h
> @@ -536,6 +536,7 @@
>
> /* MSR_IA32_VMX_MISC bits */
> #define MSR_IA32_VMX_MISC_VMWRITE_SHADOW_RO_FIELDS (1ULL << 29)
> +#define MSR_IA32_VMX_MISC_PREEMPTION_TIMER_SCALE 0x1F
> /* AMD-V MSRs */
>
> #define MSR_VM_CR 0xc0010114
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 1f1da43..870caa8
> 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -2204,7 +2204,14 @@ static __init void
> nested_vmx_setup_ctls_msrs(void) #ifdef CONFIG_X86_64
> VM_EXIT_HOST_ADDR_SPACE_SIZE |
> #endif
> - VM_EXIT_LOAD_IA32_PAT | VM_EXIT_SAVE_IA32_PAT;
> + VM_EXIT_LOAD_IA32_PAT | VM_EXIT_SAVE_IA32_PAT |
> + VM_EXIT_SAVE_VMX_PREEMPTION_TIMER;
> + if (!(nested_vmx_pinbased_ctls_high &
> PIN_BASED_VMX_PREEMPTION_TIMER))
> + nested_vmx_exit_ctls_high &=
> + (~VM_EXIT_SAVE_VMX_PREEMPTION_TIMER);
> + if (!(nested_vmx_exit_ctls_high &
> VM_EXIT_SAVE_VMX_PREEMPTION_TIMER))
> + nested_vmx_pinbased_ctls_high &=
> + (~PIN_BASED_VMX_PREEMPTION_TIMER);
The following logic is more clearly:
if(nested_vmx_pinbased_ctls_high & PIN_BASED_VMX_PREEMPTION_TIMER)
nested_vmx_exit_ctls_high |= VM_EXIT_SAVE_VMX_PREEMPTION_TIMER
BTW: I don't see nested_vmx_setup_ctls_msrs() considers the hardware's capability when expose those vmx features(not just preemption timer) to L1.
> nested_vmx_exit_ctls_high |=
> (VM_EXIT_ALWAYSON_WITHOUT_TRUE_MSR |
> VM_EXIT_LOAD_IA32_EFER);
>
> @@ -6707,6 +6714,23 @@ static void vmx_get_exit_info(struct kvm_vcpu
> *vcpu, u64 *info1, u64 *info2)
> *info2 = vmcs_read32(VM_EXIT_INTR_INFO); }
>
> +static void nested_adjust_preemption_timer(struct kvm_vcpu *vcpu) {
> + u64 delta_tsc_l1;
> + u32 preempt_val_l1, preempt_val_l2, preempt_scale;
> +
> + preempt_scale = native_read_msr(MSR_IA32_VMX_MISC) &
> + MSR_IA32_VMX_MISC_PREEMPTION_TIMER_SCALE;
> + preempt_val_l2 = vmcs_read32(VMX_PREEMPTION_TIMER_VALUE);
> + delta_tsc_l1 = kvm_x86_ops->read_l1_tsc(vcpu,
> + native_read_tsc()) - vcpu->arch.last_guest_tsc;
> + preempt_val_l1 = delta_tsc_l1 >> preempt_scale;
> + if (preempt_val_l2 - preempt_val_l1 < 0)
> + preempt_val_l2 = 0;
> + else
> + preempt_val_l2 -= preempt_val_l1;
> + vmcs_write32(VMX_PREEMPTION_TIMER_VALUE, preempt_val_l2); }
> /*
> * The guest has exited. See if we can fix it or if we need userspace
> * assistance.
> @@ -6716,6 +6740,7 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu)
> struct vcpu_vmx *vmx = to_vmx(vcpu);
> u32 exit_reason = vmx->exit_reason;
> u32 vectoring_info = vmx->idt_vectoring_info;
> + int ret;
>
> /* If guest state is invalid, start emulating */
> if (vmx->emulation_required)
> @@ -6795,12 +6820,15 @@ static int vmx_handle_exit(struct kvm_vcpu
> *vcpu)
>
> if (exit_reason < kvm_vmx_max_exit_handlers
> && kvm_vmx_exit_handlers[exit_reason])
> - return kvm_vmx_exit_handlers[exit_reason](vcpu);
> + ret = kvm_vmx_exit_handlers[exit_reason](vcpu);
> else {
> vcpu->run->exit_reason = KVM_EXIT_UNKNOWN;
> vcpu->run->hw.hardware_exit_reason = exit_reason;
> + ret = 0;
> }
> - return 0;
> + if (is_guest_mode(vcpu))
> + nested_adjust_preemption_timer(vcpu);
Move this forward to avoid the changes for ret.
> + return ret;
> }
>
> static void update_cr8_intercept(struct kvm_vcpu *vcpu, int tpr, int irr) @@
> -7518,6 +7546,7 @@ static void prepare_vmcs02(struct kvm_vcpu *vcpu,
> struct vmcs12 *vmcs12) {
> struct vcpu_vmx *vmx = to_vmx(vcpu);
> u32 exec_control;
> + u32 exit_control;
>
> vmcs_write16(GUEST_ES_SELECTOR, vmcs12->guest_es_selector);
> vmcs_write16(GUEST_CS_SELECTOR, vmcs12->guest_cs_selector); @@
> -7691,7 +7720,10 @@ static void prepare_vmcs02(struct kvm_vcpu *vcpu,
> struct vmcs12 *vmcs12)
> * we should use its exit controls. Note that VM_EXIT_LOAD_IA32_EFER
> * bits are further modified by vmx_set_efer() below.
> */
> - vmcs_write32(VM_EXIT_CONTROLS, vmcs_config.vmexit_ctrl);
> + exit_control = vmcs_config.vmexit_ctrl;
> + if (vmcs12->pin_based_vm_exec_control &
> PIN_BASED_VMX_PREEMPTION_TIMER)
> + exit_control |= VM_EXIT_SAVE_VMX_PREEMPTION_TIMER;
> + vmcs_write32(VM_EXIT_CONTROLS, exit_control);
And here should be problem if host doesn't support VM_EXIT_SAVE_VMX_PREEMPTION_TIMER.
>
> /* vmcs12's VM_ENTRY_LOAD_IA32_EFER and VM_ENTRY_IA32E_MODE
> are
> * emulated by vmx_set_efer(), below.
> @@ -8090,6 +8122,17 @@ static void prepare_vmcs12(struct kvm_vcpu *vcpu,
> struct vmcs12 *vmcs12)
> vmcs12->guest_pending_dbg_exceptions =
> vmcs_readl(GUEST_PENDING_DBG_EXCEPTIONS);
>
> + if (vmcs12->pin_based_vm_exec_control &
> + PIN_BASED_VMX_PREEMPTION_TIMER) {
> + if (vmcs12->vm_exit_controls &
> + VM_EXIT_SAVE_VMX_PREEMPTION_TIMER)
> + vmcs12->vmx_preemption_timer_value =
> + vmcs_read32(VMX_PREEMPTION_TIMER_VALUE);
> + else
> + vmcs_write32(VMX_PREEMPTION_TIMER_VALUE,
> + vmcs12->vmx_preemption_timer_value);
Why write it to vmcs directly if VM_EXIT_SAVE_VMX_PREEMPTION_TIMER not set?
> + }
> +
> /*
> * In some cases (usually, nested EPT), L2 is allowed to change its
> * own CR3 without exiting. If it has changed it, we must keep it.
> --
> 1.7.9.5
>
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Best regards,
Yang
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