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Message-ID: <87lfosp9xs.fsf@vitty.brq.redhat.com>
Date: Mon, 24 Feb 2020 11:16:15 +0100
From: Vitaly Kuznetsov <vkuznets@...hat.com>
To: Xiaoyao Li <xiaoyao.li@...el.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
Paolo Bonzini <pbonzini@...hat.com>,
Sean Christopherson <sean.j.christopherson@...el.com>,
Wanpeng Li <wanpengli@...cent.com>,
Jim Mattson <jmattson@...gle.com>,
Joerg Roedel <joro@...tes.org>
Subject: Re: [PATCH 1/2] kvm: vmx: Use basic exit reason to check if it's the specific VM EXIT
Xiaoyao Li <xiaoyao.li@...el.com> writes:
> Current kvm uses the 32-bit exit reason to check if it's any specific VM
> EXIT, however only the low 16-bit of VM EXIT REASON acts as the basic
> exit reason.
>
> Introduce Macro basic(exit_reaso)
"exit_reason"
> to help retrieve the basic exit reason
> from VM EXIT REASON, and use the basic exit reason for checking and
> indexing the exit hanlder.
>
> Signed-off-by: Xiaoyao Li <xiaoyao.li@...el.com>
> ---
> arch/x86/kvm/vmx/vmx.c | 44 ++++++++++++++++++++++--------------------
> arch/x86/kvm/vmx/vmx.h | 2 ++
> 2 files changed, 25 insertions(+), 21 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 9a6664886f2e..85da72d4dc92 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -1584,7 +1584,7 @@ static int skip_emulated_instruction(struct kvm_vcpu *vcpu)
> * i.e. we end up advancing IP with some random value.
> */
> if (!static_cpu_has(X86_FEATURE_HYPERVISOR) ||
> - to_vmx(vcpu)->exit_reason != EXIT_REASON_EPT_MISCONFIG) {
> + basic(to_vmx(vcpu)->exit_reason) != EXIT_REASON_EPT_MISCONFIG) {
"basic" word is probably 'too basic' to be used for this purpose. Even
if we need a macro for it (I'm not really convinced it improves the
readability), I'd suggest we name it 'basic_exit_reason()' instead.
> rip = kvm_rip_read(vcpu);
> rip += vmcs_read32(VM_EXIT_INSTRUCTION_LEN);
> kvm_rip_write(vcpu, rip);
> @@ -5797,6 +5797,7 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu,
> {
> struct vcpu_vmx *vmx = to_vmx(vcpu);
> u32 exit_reason = vmx->exit_reason;
> + u16 basic_exit_reason = basic(exit_reason);
I don't think renaming local variable is needed, let's just do
'u16 exit_reason = basic_exit_reason(vmx->exit_reason)' and keep the
rest of the code as-is.
> u32 vectoring_info = vmx->idt_vectoring_info;
>
> trace_kvm_exit(exit_reason, vcpu, KVM_ISA_VMX);
> @@ -5842,17 +5843,17 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu,
> * will cause infinite loop.
> */
> if ((vectoring_info & VECTORING_INFO_VALID_MASK) &&
> - (exit_reason != EXIT_REASON_EXCEPTION_NMI &&
> - exit_reason != EXIT_REASON_EPT_VIOLATION &&
> - exit_reason != EXIT_REASON_PML_FULL &&
> - exit_reason != EXIT_REASON_TASK_SWITCH)) {
> + (basic_exit_reason != EXIT_REASON_EXCEPTION_NMI &&
> + basic_exit_reason != EXIT_REASON_EPT_VIOLATION &&
> + basic_exit_reason != EXIT_REASON_PML_FULL &&
> + basic_exit_reason != EXIT_REASON_TASK_SWITCH)) {
> vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
> vcpu->run->internal.suberror = KVM_INTERNAL_ERROR_DELIVERY_EV;
> vcpu->run->internal.ndata = 3;
> vcpu->run->internal.data[0] = vectoring_info;
> vcpu->run->internal.data[1] = exit_reason;
> vcpu->run->internal.data[2] = vcpu->arch.exit_qualification;
> - if (exit_reason == EXIT_REASON_EPT_MISCONFIG) {
> + if (basic_exit_reason == EXIT_REASON_EPT_MISCONFIG) {
> vcpu->run->internal.ndata++;
> vcpu->run->internal.data[3] =
> vmcs_read64(GUEST_PHYSICAL_ADDRESS);
> @@ -5884,32 +5885,32 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu,
> return 1;
> }
>
> - if (exit_reason >= kvm_vmx_max_exit_handlers)
> + if (basic_exit_reason >= kvm_vmx_max_exit_handlers)
> goto unexpected_vmexit;
> #ifdef CONFIG_RETPOLINE
> - if (exit_reason == EXIT_REASON_MSR_WRITE)
> + if (basic_exit_reason == EXIT_REASON_MSR_WRITE)
> return kvm_emulate_wrmsr(vcpu);
> - else if (exit_reason == EXIT_REASON_PREEMPTION_TIMER)
> + else if (basic_exit_reason == EXIT_REASON_PREEMPTION_TIMER)
> return handle_preemption_timer(vcpu);
> - else if (exit_reason == EXIT_REASON_INTERRUPT_WINDOW)
> + else if (basic_exit_reason == EXIT_REASON_INTERRUPT_WINDOW)
> return handle_interrupt_window(vcpu);
> - else if (exit_reason == EXIT_REASON_EXTERNAL_INTERRUPT)
> + else if (basic_exit_reason == EXIT_REASON_EXTERNAL_INTERRUPT)
> return handle_external_interrupt(vcpu);
> - else if (exit_reason == EXIT_REASON_HLT)
> + else if (basic_exit_reason == EXIT_REASON_HLT)
> return kvm_emulate_halt(vcpu);
> - else if (exit_reason == EXIT_REASON_EPT_MISCONFIG)
> + else if (basic_exit_reason == EXIT_REASON_EPT_MISCONFIG)
> return handle_ept_misconfig(vcpu);
> #endif
>
> - exit_reason = array_index_nospec(exit_reason,
> + basic_exit_reason = array_index_nospec(basic_exit_reason,
> kvm_vmx_max_exit_handlers);
> - if (!kvm_vmx_exit_handlers[exit_reason])
> + if (!kvm_vmx_exit_handlers[basic_exit_reason])
> goto unexpected_vmexit;
>
> - return kvm_vmx_exit_handlers[exit_reason](vcpu);
> + return kvm_vmx_exit_handlers[basic_exit_reason](vcpu);
>
> unexpected_vmexit:
> - vcpu_unimpl(vcpu, "vmx: unexpected exit reason 0x%x\n", exit_reason);
> + vcpu_unimpl(vcpu, "vmx: unexpected exit reason 0x%x\n", basic_exit_reason);
> dump_vmcs();
> vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
> vcpu->run->internal.suberror =
> @@ -6241,13 +6242,14 @@ static void vmx_handle_exit_irqoff(struct kvm_vcpu *vcpu,
> enum exit_fastpath_completion *exit_fastpath)
> {
> struct vcpu_vmx *vmx = to_vmx(vcpu);
> + u16 basic_exit_reason = basic(vmx->exit_reason);
Here I'd suggest we also use the same
'u16 exit_reason = basic_exit_reason(vmx->exit_reason)'
as above.
>
> - if (vmx->exit_reason == EXIT_REASON_EXTERNAL_INTERRUPT)
> + if (basic_exit_reason == EXIT_REASON_EXTERNAL_INTERRUPT)
> handle_external_interrupt_irqoff(vcpu);
> - else if (vmx->exit_reason == EXIT_REASON_EXCEPTION_NMI)
> + else if (basic_exit_reason == EXIT_REASON_EXCEPTION_NMI)
> handle_exception_nmi_irqoff(vmx);
> else if (!is_guest_mode(vcpu) &&
> - vmx->exit_reason == EXIT_REASON_MSR_WRITE)
> + basic_exit_reason == EXIT_REASON_MSR_WRITE)
> *exit_fastpath = handle_fastpath_set_msr_irqoff(vcpu);
> }
>
> @@ -6621,7 +6623,7 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu)
> vmx->idt_vectoring_info = 0;
>
> vmx->exit_reason = vmx->fail ? 0xdead : vmcs_read32(VM_EXIT_REASON);
> - if ((u16)vmx->exit_reason == EXIT_REASON_MCE_DURING_VMENTRY)
> + if (basic(vmx->exit_reason) == EXIT_REASON_MCE_DURING_VMENTRY)
> kvm_machine_check();
>
> if (vmx->fail || (vmx->exit_reason & VMX_EXIT_REASONS_FAILED_VMENTRY))
> diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
> index 7f42cf3dcd70..c6ba33eedb59 100644
> --- a/arch/x86/kvm/vmx/vmx.h
> +++ b/arch/x86/kvm/vmx/vmx.h
> @@ -22,6 +22,8 @@ extern u32 get_umwait_control_msr(void);
>
> #define X2APIC_MSR(r) (APIC_BASE_MSR + ((r) >> 4))
>
> +#define basic(exit_reason) ((u16)(exit_reason))
> +
> #ifdef CONFIG_X86_64
> #define NR_SHARED_MSRS 7
> #else
--
Vitaly
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