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Message-ID: <51768b50-96ac-49a7-a63b-02d2b94c2c6a@zytor.com>
Date: Mon, 1 Jul 2024 10:03:58 -0700
From: Xin Li <xin@...or.com>
To: Jacob Pan <jacob.jun.pan@...ux.intel.com>
Cc: X86 Kernel <x86@...nel.org>, Sean Christopherson <seanjc@...gle.com>,
LKML <linux-kernel@...r.kernel.org>,
Thomas Gleixner <tglx@...utronix.de>,
Dave Hansen <dave.hansen@...el.com>, "H. Peter Anvin" <hpa@...or.com>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
Xin Li <xin3.li@...el.com>, linux-perf-users@...r.kernel.org,
Peter Zijlstra <peterz@...radead.org>,
Paolo Bonzini <pbonzini@...hat.com>, Tony Luck <tony.luck@...el.com>,
Andy Lutomirski <luto@...nel.org>, acme@...nel.org,
kan.liang@...ux.intel.com, Andi Kleen
<andi.kleen@...el.com>,
"Mehta, Sohil" <sohil.mehta@...el.com>,
Zeng Guang <guang.zeng@...el.com>
Subject: Re: [PATCH v3 07/11] KVM: VMX: Handle NMI Source report in VM exit
On 7/1/2024 8:45 AM, Jacob Pan wrote:
>
> On Fri, 28 Jun 2024 21:07:04 -0700, Xin Li <xin@...or.com> wrote:
>
>> On 6/28/2024 1:18 PM, Jacob Pan wrote:
>>> From: Zeng Guang <guang.zeng@...el.com>
>>>
>>> If the "NMI exiting" VM-execution control is 1, the value of the 16-bit
>>> NMI source vector is saved in the exit-qualification field in the VMCS
>>> when VM exits occur on CPUs that support NMI source.
>>>
>>> KVM that is aware of NMI-source reporting will push the bitmask of NMI
>>> source vectors as the exceptoin event data field on the stack for then
>>> entry of FRED exception. Subsequently, the host NMI exception handler
>>> is invoked which will process NMI source information in the event data.
>>> This operation is independent of vCPU FRED enabling status.
>>>
>>> Signed-off-by: Zeng Guang <guang.zeng@...el.com>
>>> Signed-off-by: Jacob Pan <jacob.jun.pan@...ux.intel.com>
>>> ---
>>> arch/x86/entry/entry_64_fred.S | 2 +-
>>> arch/x86/kvm/vmx/vmx.c | 11 ++++++++---
>>> 2 files changed, 9 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/arch/x86/entry/entry_64_fred.S
>>> b/arch/x86/entry/entry_64_fred.S index a02bc6f3d2e6..0d934a3fcaf8 100644
>>> --- a/arch/x86/entry/entry_64_fred.S
>>> +++ b/arch/x86/entry/entry_64_fred.S
>>> @@ -92,7 +92,7 @@ SYM_FUNC_START(asm_fred_entry_from_kvm)
>>> * +--------+-----------------+
>>> */
>>> push $0 /* Reserved, must be 0
>>> */
>>> - push $0 /* Event data, 0 for
>>> IRQ/NMI */
>>> + push %rsi /* Event data for IRQ/NMI */
>>> push %rdi /* fred_ss handed in by the
>>> caller */ push %rbp
>>> pushf
>>
>> This belongs to the previous patch, it is part of the host changes.
> right, will do.
>
>>
>>> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
>>> index 4e7b36081b76..6719c598fa5f 100644
>>> --- a/arch/x86/kvm/vmx/vmx.c
>>> +++ b/arch/x86/kvm/vmx/vmx.c
>>> @@ -7331,10 +7331,15 @@ static noinstr void vmx_vcpu_enter_exit(struct
>>> kvm_vcpu *vcpu, if ((u16)vmx->exit_reason.basic ==
>>> EXIT_REASON_EXCEPTION_NMI && is_nmi(vmx_get_intr_info(vcpu))) {
>>> kvm_before_interrupt(vcpu, KVM_HANDLING_NMI);
>>> - if (cpu_feature_enabled(X86_FEATURE_FRED))
>>> - fred_entry_from_kvm(EVENT_TYPE_NMI,
>>> NMI_VECTOR, 0);
>>> - else
>>> + if (cpu_feature_enabled(X86_FEATURE_FRED)) {
>>> + unsigned long edata = 0;
>>> +
>>> + if
>>> (cpu_feature_enabled(X86_FEATURE_NMI_SOURCE))
>>> + edata = vmx_get_exit_qual(vcpu);
>>> + fred_entry_from_kvm(EVENT_TYPE_NMI,
>>> NMI_VECTOR, edata);
>>
>> Simply do fred_entry_from_kvm(EVENT_TYPE_NMI, NMI_VECTOR,
>> vmx_get_exit_qual(vcpu))?
> I don't have strong preference but having a local variable improves
> readability IMHO.
My point was, do we actually need this check:
(cpu_feature_enabled(X86_FEATURE_NMI_SOURCE)?
I don't have a strong preference either.
>
>>> + } else {
>>> vmx_do_nmi_irqoff();
>>> + }
>>> kvm_after_interrupt(vcpu);
>>> }
>>>
>>
>
>
> Thanks,
>
> Jacob
>
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