linux-kernel - Re: [PATCH 17/28] KVM: SVM: Manually recalc all MSR intercepts on userspace MSR filter change

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Message-ID: <e5e1fb2715a98f24ba69cc4da5c30777633f6f62.camel@gmail.com>
Date: Sat, 31 May 2025 20:01:18 +0200
From: Francesco Lavra <francescolavra.fl@...il.com>
To: seanjc@...gle.com
Cc: bp@...en8.de, chao.gao@...el.com, dapeng1.mi@...ux.intel.com, 
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org, pbonzini@...hat.com, 
	xin@...or.com
Subject: Re: [PATCH 17/28] KVM: SVM: Manually recalc all MSR intercepts on
 userspace MSR filter change

On 2025-05-29 at 23:40, Sean Christopherson wrote:
> @@ -81,70 +79,6 @@ static uint64_t osvw_len = 4, osvw_status;
>  
>  static DEFINE_PER_CPU(u64, current_tsc_ratio);
>  
> -static const u32 direct_access_msrs[] = {
> -	MSR_STAR,
> -	MSR_IA32_SYSENTER_CS,
> -	MSR_IA32_SYSENTER_EIP,
> -	MSR_IA32_SYSENTER_ESP,
> -#ifdef CONFIG_X86_64
> -	MSR_GS_BASE,
> -	MSR_FS_BASE,
> -	MSR_KERNEL_GS_BASE,
> -	MSR_LSTAR,
> -	MSR_CSTAR,
> -	MSR_SYSCALL_MASK,
> -#endif
> -	MSR_IA32_SPEC_CTRL,
> -	MSR_IA32_PRED_CMD,
> -	MSR_IA32_FLUSH_CMD,
> -	MSR_IA32_DEBUGCTLMSR,
> -	MSR_IA32_LASTBRANCHFROMIP,
> -	MSR_IA32_LASTBRANCHTOIP,
> -	MSR_IA32_LASTINTFROMIP,
> -	MSR_IA32_LASTINTTOIP,
> -	MSR_IA32_XSS,
> -	MSR_EFER,
> -	MSR_IA32_CR_PAT,
> -	MSR_AMD64_SEV_ES_GHCB,
> -	MSR_TSC_AUX,
> -	X2APIC_MSR(APIC_ID),
> -	X2APIC_MSR(APIC_LVR),
> -	X2APIC_MSR(APIC_TASKPRI),
> -	X2APIC_MSR(APIC_ARBPRI),
> -	X2APIC_MSR(APIC_PROCPRI),
> -	X2APIC_MSR(APIC_EOI),
> -	X2APIC_MSR(APIC_RRR),
> -	X2APIC_MSR(APIC_LDR),
> -	X2APIC_MSR(APIC_DFR),
> -	X2APIC_MSR(APIC_SPIV),
> -	X2APIC_MSR(APIC_ISR),
> -	X2APIC_MSR(APIC_TMR),
> -	X2APIC_MSR(APIC_IRR),
> -	X2APIC_MSR(APIC_ESR),
> -	X2APIC_MSR(APIC_ICR),
> -	X2APIC_MSR(APIC_ICR2),
> -
> -	/*
> -	 * Note:
> -	 * AMD does not virtualize APIC TSC-deadline timer mode, but it
> is
> -	 * emulated by KVM. When setting APIC LVTT (0x832) register bit
> 18,
> -	 * the AVIC hardware would generate GP fault. Therefore, always
> -	 * intercept the MSR 0x832, and do not setup direct_access_msr.
> -	 */
> -	X2APIC_MSR(APIC_LVTTHMR),
> -	X2APIC_MSR(APIC_LVTPC),
> -	X2APIC_MSR(APIC_LVT0),
> -	X2APIC_MSR(APIC_LVT1),
> -	X2APIC_MSR(APIC_LVTERR),
> -	X2APIC_MSR(APIC_TMICT),
> -	X2APIC_MSR(APIC_TMCCT),
> -	X2APIC_MSR(APIC_TDCR),
> -};
> -
> -static_assert(ARRAY_SIZE(direct_access_msrs) ==
> -	      MAX_DIRECT_ACCESS_MSRS - 6 * !IS_ENABLED(CONFIG_X86_64));
> -#undef MAX_DIRECT_ACCESS_MSRS

The MAX_DIRECT_ACCESS_MSRS define should now be removed from
arch/x86/kvm/svm/svm.harch/x86/kvm/svm/svm.h, since it's no longer used.