linux-kernel - Re: [PATCH v2 5/7] KVM: SVM: hyper-v: Remote TLB flush for SVM

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Message-ID: <87sg3q7g7b.fsf@vitty.brq.redhat.com>
Date:   Fri, 16 Apr 2021 11:04:56 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Vineeth Pillai <viremana@...ux.microsoft.com>
Cc:     Vineeth Pillai <viremana@...ux.microsoft.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "K. Y. Srinivasan" <kys@...rosoft.com>, x86@...nel.org,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-hyperv@...r.kernel.org,
        Lan Tianyu <Tianyu.Lan@...rosoft.com>,
        Michael Kelley <mikelley@...rosoft.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, Wei Liu <wei.liu@...nel.org>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>
Subject: Re: [PATCH v2 5/7] KVM: SVM: hyper-v: Remote TLB flush for SVM

Vineeth Pillai <viremana@...ux.microsoft.com> writes:

> Enable remote TLB flush for SVM.
>
> Signed-off-by: Vineeth Pillai <viremana@...ux.microsoft.com>
> ---
>  arch/x86/kvm/svm/svm.c | 37 +++++++++++++++++++++++++++++++++++++
>  1 file changed, 37 insertions(+)
>
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index 2ad1f55c88d0..de141d5ae5fb 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -37,6 +37,7 @@
>  #include <asm/spec-ctrl.h>
>  #include <asm/cpu_device_id.h>
>  #include <asm/traps.h>
> +#include <asm/mshyperv.h>
>  
>  #include <asm/virtext.h>
>  #include "trace.h"
> @@ -44,6 +45,8 @@
>  #include "svm.h"
>  #include "svm_ops.h"
>  
> +#include "hyperv.h"
> +
>  #define __ex(x) __kvm_handle_fault_on_reboot(x)
>  
>  MODULE_AUTHOR("Qumranet");
> @@ -931,6 +934,8 @@ static __init void svm_set_cpu_caps(void)
>  		kvm_cpu_cap_set(X86_FEATURE_VIRT_SSBD);
>  }
>  
> +static struct kvm_x86_ops svm_x86_ops;
> +
>  static __init int svm_hardware_setup(void)
>  {
>  	int cpu;
> @@ -1000,6 +1005,16 @@ static __init int svm_hardware_setup(void)
>  	kvm_configure_mmu(npt_enabled, get_max_npt_level(), PG_LEVEL_1G);
>  	pr_info("kvm: Nested Paging %sabled\n", npt_enabled ? "en" : "dis");
>  
> +#if IS_ENABLED(CONFIG_HYPERV)
> +	if (ms_hyperv.nested_features & HV_X64_NESTED_ENLIGHTENED_TLB
> +	    && npt_enabled) {
> +		pr_info("kvm: Hyper-V enlightened NPT TLB flush enabled\n");
> +		svm_x86_ops.tlb_remote_flush = kvm_hv_remote_flush_tlb;
> +		svm_x86_ops.tlb_remote_flush_with_range =
> +				kvm_hv_remote_flush_tlb_with_range;
> +	}
> +#endif
> +
>  	if (nrips) {
>  		if (!boot_cpu_has(X86_FEATURE_NRIPS))
>  			nrips = false;
> @@ -1120,6 +1135,21 @@ static void svm_check_invpcid(struct vcpu_svm *svm)
>  	}
>  }
>  
> +#if IS_ENABLED(CONFIG_HYPERV)
> +static void hv_init_vmcb(struct vmcb *vmcb)
> +{
> +	struct hv_enlightenments *hve = &vmcb->hv_enlightenments;
> +
> +	if (npt_enabled &&
> +	    ms_hyperv.nested_features & HV_X64_NESTED_ENLIGHTENED_TLB)

Nitpick: we can probably have a 'static inline' for 

 "npt_enabled && ms_hyperv.nested_features & HV_X64_NESTED_ENLIGHTENED_TLB"

e.g. 'hv_svm_enlightened_tlbflush()'

> +		hve->hv_enlightenments_control.enlightened_npt_tlb = 1;
> +}
> +#else
> +static inline void hv_init_vmcb(struct vmcb *vmcb)
> +{
> +}
> +#endif
> +
>  static void init_vmcb(struct vcpu_svm *svm)
>  {
>  	struct vmcb_control_area *control = &svm->vmcb->control;
> @@ -1282,6 +1312,8 @@ static void init_vmcb(struct vcpu_svm *svm)
>  		}
>  	}
>  
> +	hv_init_vmcb(svm->vmcb);
> +
>  	vmcb_mark_all_dirty(svm->vmcb);
>  
>  	enable_gif(svm);
> @@ -3975,6 +4007,11 @@ static void svm_load_mmu_pgd(struct kvm_vcpu *vcpu, unsigned long root,
>  		svm->vmcb->control.nested_cr3 = cr3;
>  		vmcb_mark_dirty(svm->vmcb, VMCB_NPT);
>  
> +#if IS_ENABLED(CONFIG_HYPERV)
> +		if (kvm_x86_ops.tlb_remote_flush)
> +			kvm_update_arch_tdp_pointer(vcpu->kvm, vcpu, cr3);
> +#endif
> +
>  		/* Loading L2's CR3 is handled by enter_svm_guest_mode.  */
>  		if (!test_bit(VCPU_EXREG_CR3, (ulong *)&vcpu->arch.regs_avail))
>  			return;

-- 
Vitaly