linux-kernel - Re: [PATCH v4 07/38] perf: core/x86: Register a new vector for KVM GUEST PMI

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Message-ID: <e8e8ed55-7614-49be-9a1e-069738dbb2ef@linux.intel.com>
Date: Thu, 15 May 2025 09:40:47 +0800
From: "Mi, Dapeng" <dapeng1.mi@...ux.intel.com>
To: Sean Christopherson <seanjc@...gle.com>,
 Mingwei Zhang <mizhang@...gle.com>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
 Arnaldo Carvalho de Melo <acme@...nel.org>,
 Namhyung Kim <namhyung@...nel.org>, Paolo Bonzini <pbonzini@...hat.com>,
 Mark Rutland <mark.rutland@....com>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
 Jiri Olsa <jolsa@...nel.org>, Ian Rogers <irogers@...gle.com>,
 Adrian Hunter <adrian.hunter@...el.com>, Liang@...gle.com,
 Kan <kan.liang@...ux.intel.com>, "H. Peter Anvin" <hpa@...or.com>,
 linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
 kvm@...r.kernel.org, linux-kselftest@...r.kernel.org,
 Yongwei Ma <yongwei.ma@...el.com>,
 Xiong Zhang <xiong.y.zhang@...ux.intel.com>,
 Jim Mattson <jmattson@...gle.com>, Sandipan Das <sandipan.das@....com>,
 Zide Chen <zide.chen@...el.com>, Eranian Stephane <eranian@...gle.com>,
 Shukla Manali <Manali.Shukla@....com>,
 Nikunj Dadhania <nikunj.dadhania@....com>
Subject: Re: [PATCH v4 07/38] perf: core/x86: Register a new vector for KVM
 GUEST PMI

On 5/15/2025 7:24 AM, Sean Christopherson wrote:
> On Mon, Mar 24, 2025, Mingwei Zhang wrote:
>> diff --git a/arch/x86/include/asm/idtentry.h b/arch/x86/include/asm/idtentry.h
>> index ad5c68f0509d..b0cb3220e1bb 100644
>> --- a/arch/x86/include/asm/idtentry.h
>> +++ b/arch/x86/include/asm/idtentry.h
>> @@ -745,6 +745,7 @@ DECLARE_IDTENTRY_SYSVEC(IRQ_WORK_VECTOR,		sysvec_irq_work);
>>  DECLARE_IDTENTRY_SYSVEC(POSTED_INTR_VECTOR,		sysvec_kvm_posted_intr_ipi);
>>  DECLARE_IDTENTRY_SYSVEC(POSTED_INTR_WAKEUP_VECTOR,	sysvec_kvm_posted_intr_wakeup_ipi);
>>  DECLARE_IDTENTRY_SYSVEC(POSTED_INTR_NESTED_VECTOR,	sysvec_kvm_posted_intr_nested_ipi);
>> +DECLARE_IDTENTRY_SYSVEC(KVM_GUEST_PMI_VECTOR,	        sysvec_kvm_guest_pmi_handler);
> I would prefer to keep KVM out of the name, and as mentioned in the previous patch,
> route this through perf.

Sure.

>
>>  #else
>>  # define fred_sysvec_kvm_posted_intr_ipi		NULL
>>  # define fred_sysvec_kvm_posted_intr_wakeup_ipi		NULL
> Y'all forgot to wire up the FRED handling.  I.e. the mediated PMI IRQs would get
> treated as spurious when running with FRED.

Oh, yes. we missed that. we would look at it. Thanks for reminding.

>
>> diff --git a/arch/x86/include/asm/irq_vectors.h b/arch/x86/include/asm/irq_vectors.h
>> index 47051871b436..250cdab11306 100644
>> --- a/arch/x86/include/asm/irq_vectors.h
>> +++ b/arch/x86/include/asm/irq_vectors.h
>> @@ -77,7 +77,10 @@
>>   */
>>  #define IRQ_WORK_VECTOR			0xf6
>>  
>> -/* 0xf5 - unused, was UV_BAU_MESSAGE */
>> +#if IS_ENABLED(CONFIG_KVM)
>> +#define KVM_GUEST_PMI_VECTOR		0xf5
>> +#endif
> Conditionally defining the vector sounds good on paper, but its problematic, e.g.
> for connecting the handler to FRED's array, and doesn't really add much value.
>
>>  #define DEFERRED_ERROR_VECTOR		0xf4
>>  
>>  /* Vector on which hypervisor callbacks will be delivered */
>> diff --git a/arch/x86/kernel/idt.c b/arch/x86/kernel/idt.c
>> index f445bec516a0..0bec4c7e2308 100644
>> --- a/arch/x86/kernel/idt.c
>> +++ b/arch/x86/kernel/idt.c
>> @@ -157,6 +157,7 @@ static const __initconst struct idt_data apic_idts[] = {
>>  	INTG(POSTED_INTR_VECTOR,		asm_sysvec_kvm_posted_intr_ipi),
>>  	INTG(POSTED_INTR_WAKEUP_VECTOR,		asm_sysvec_kvm_posted_intr_wakeup_ipi),
>>  	INTG(POSTED_INTR_NESTED_VECTOR,		asm_sysvec_kvm_posted_intr_nested_ipi),