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Message-ID: <716806df-c0e4-43d5-b082-627d2c312f53@oracle.com>
Date: Mon, 24 Feb 2020 16:27:34 -0800
From: Krish Sadhukhan <krish.sadhukhan@...cle.com>
To: Xiaoyao Li <xiaoyao.li@...el.com>,
Vitaly Kuznetsov <vkuznets@...hat.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
On 02/24/2020 04:01 AM, Xiaoyao Li wrote:
> On 2/24/2020 6:16 PM, Vitaly Kuznetsov wrote:
>> 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"
>
> Ah, will correct it in v2.
>
>>> 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.
>
> Agreed.
>
>>> 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.
>
> No, we can't do this.
>
> It's not just renaming local variable, the full 32-bit exit reason is
> used elsewhere in this function that needs the upper 16-bit.
>
> Here variable basic_exit_reason is added for the cases where only
> basic exit reason number is needed.
>
>>> 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))
We have a macro for bit 31,
VMX_EXIT_REASONS_FAILED_VMENTRY 0x80000000
Does it make sense to define a macro like that instead ? Say,
VMX_BASIC_EXIT_REASON 0x0000ffff
and then we do,
u32 exit_reason = vmx->exit_reason;
u16 basic_exit_reason = exit_reason & VMX_BASIC_EXIT_REASON;
>>> +
>>> #ifdef CONFIG_X86_64
>>> #define NR_SHARED_MSRS 7
>>> #else
>>
>
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