Il 06/09/2013 04:04, Arthur Chunqi Li ha scritto:
> 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>
> ---
> ChangeLog to v3:
> Move nested_adjust_preemption_timer to the latest place just before vmenter.
> Some minor changes.
>
> arch/x86/include/uapi/asm/msr-index.h | 1 +
> arch/x86/kvm/vmx.c | 49 +++++++++++++++++++++++++++++++--
> 2 files changed, 48 insertions(+), 2 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..f364d16 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -374,6 +374,8 @@ struct nested_vmx {
> */
> struct page *apic_access_page;
> u64 msr_ia32_feature_control;
> + /* Set if vmexit is L2->L1 */
> + bool nested_vmx_exit;
> };
>
> #define POSTED_INTR_ON 0
> @@ -2204,7 +2206,17 @@ 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)) {
Align this under the other "!". Also, I prefer to have one long line
for the whole "!(... & ...) ||" (and likewise below), but I don't know
if Gleb agrees
> + nested_vmx_exit_ctls_high &=
> + (~VM_EXIT_SAVE_VMX_PREEMPTION_TIMER);
Please remove parentheses around ~VM_EXIT_SAVE_VMX_PREEMPTION_TIMER, and
likewise elsewhere in the patch.
> + nested_vmx_pinbased_ctls_high &=
> + (~PIN_BASED_VMX_PREEMPTION_TIMER);
> + }
> nested_vmx_exit_ctls_high |= (VM_EXIT_ALWAYSON_WITHOUT_TRUE_MSR |
> VM_EXIT_LOAD_IA32_EFER);
>
> @@ -6707,6 +6719,24 @@ 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;
Should this exit immediately if the preemption timer pin-based control
is disabled?
> + 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;
Please format this like:
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)
> + preempt_val_l2 = 0;
> + else
> + preempt_val_l2 -= preempt_val_l1;
> + vmcs_write32(VMX_PREEMPTION_TIMER_VALUE, preempt_val_l2);
Did you test that a value of 0 triggers an immediate exit, rather than
counting down by 2^32? Perhaps it's safer to limit the value to 1
instead of 0.
> +}
> +
> /*
> * The guest has exited. See if we can fix it or if we need userspace
> * assistance.
> @@ -6736,9 +6766,11 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu)
> vmx->nested.nested_run_pending = 0;
>
> if (is_guest_mode(vcpu) && nested_vmx_exit_handled(vcpu)) {
> + vmx->nested.nested_vmx_exit = true;
I think this assignment should be in nested_vmx_vmexit, since it is
called from other places as well.
> nested_vmx_vmexit(vcpu);
> return 1;
> }
> + vmx->nested.nested_vmx_exit = false;
>
> if (exit_reason & VMX_EXIT_REASONS_FAILED_VMENTRY) {
> vcpu->run->exit_reason = KVM_EXIT_FAIL_ENTRY;
> @@ -7132,6 +7164,8 @@ static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu)
> debugctlmsr = get_debugctlmsr();
>
> vmx->__launched = vmx->loaded_vmcs->launched;
> + if (is_guest_mode(vcpu) && !(vmx->nested.nested_vmx_exit))
> + nested_adjust_preemption_timer(vcpu);
Please leave the assignment to __launched last, since it's already
initializing the asm below.
I don't like the is_guest_mode check here... Maybe it's
micro-optimizing, but I wonder if we already do too many checks in
vmx_vcpu_run... For example, is_guest_mode could be changed (I think)
to a check for "vmx->loaded_vmcs == &vmx->vmcs1".
Alternatively, we could change nested_vmx_exit to an enum in struct
vcpu_vmx (with values for L0->L1, L0->L2, L1->L2) that is initialized in
vmx_handle_exit. Then we could check directly for L0->L2 and not adjust
the preemption timer in other cases. In fact, I suspect this enum could
replace HF_GUEST_MASK altogether. However, this would require some
other, more complicated, changes to svm.c.
Gleb, what do you think?
Paolo
> asm(
> /* Store host registers */
> "push %%" _ASM_DX "; push %%" _ASM_BP ";"
> @@ -7518,6 +7552,7 @@ 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 +7726,10 @@ 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);
>
> /* vmcs12's VM_ENTRY_LOAD_IA32_EFER and VM_ENTRY_IA32E_MODE are
> * emulated by vmx_set_efer(), below.
> @@ -8090,6 +8128,13 @@ 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) &&
> + (vmcs12->vm_exit_controls &
> + VM_EXIT_SAVE_VMX_PREEMPTION_TIMER))
> + vmcs12->vmx_preemption_timer_value =
> + vmcs_read32(VMX_PREEMPTION_TIMER_VALUE);
> +
> /*
> * 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.
>
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