linux-kernel - RE: [PATCH v5 5/7] KVM: SVM: hyper-v: Remote TLB flush for SVM

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Date:   Tue, 8 Jun 2021 17:33:56 +0000
From:   Michael Kelley <mikelley@...rosoft.com>
To:     Vineeth Pillai <viremana@...ux.microsoft.com>,
        Tianyu Lan <Tianyu.Lan@...rosoft.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        vkuznets <vkuznets@...hat.com>,
        Tom Lendacky <thomas.lendacky@....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>
CC:     "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        KY Srinivasan <kys@...rosoft.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>
Subject: RE: [PATCH v5 5/7] KVM: SVM: hyper-v: Remote TLB flush for SVM

From: Vineeth Pillai <viremana@...ux.microsoft.com> Sent: Thursday, June 3, 2021 8:15 AM
> 
> Enable remote TLB flush for SVM.
> 
> Signed-off-by: Vineeth Pillai <viremana@...ux.microsoft.com>
> ---
>  arch/x86/kvm/svm/svm.c          |  9 +++++
>  arch/x86/kvm/svm/svm_onhyperv.h | 66 +++++++++++++++++++++++++++++++++
>  2 files changed, 75 insertions(+)
>  create mode 100644 arch/x86/kvm/svm/svm_onhyperv.h
> 
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index b649f92287a2..a39865dbc200 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -43,6 +43,9 @@
>  #include "svm.h"
>  #include "svm_ops.h"
> 
> +#include "kvm_onhyperv.h"
> +#include "svm_onhyperv.h"
> +
>  #define __ex(x) __kvm_handle_fault_on_reboot(x)
> 
>  MODULE_AUTHOR("Qumranet");
> @@ -992,6 +995,8 @@ static __init int svm_hardware_setup(void)
>  	/* Note, SEV setup consumes npt_enabled. */
>  	sev_hardware_setup();
> 
> +	svm_hv_hardware_setup();
> +
>  	svm_adjust_mmio_mask();
> 
>  	for_each_possible_cpu(cpu) {
> @@ -1276,6 +1281,8 @@ static void init_vmcb(struct kvm_vcpu *vcpu)
>  		}
>  	}
> 
> +	svm_hv_init_vmcb(svm->vmcb);
> +
>  	vmcb_mark_all_dirty(svm->vmcb);
> 
>  	enable_gif(svm);
> @@ -3884,6 +3891,8 @@ static void svm_load_mmu_pgd(struct kvm_vcpu *vcpu, hpa_t
> root_hpa,
>  		svm->vmcb->control.nested_cr3 = __sme_set(root_hpa);
>  		vmcb_mark_dirty(svm->vmcb, VMCB_NPT);
> 
> +		hv_track_root_tdp(vcpu, root_hpa);
> +
>  		/* Loading L2's CR3 is handled by enter_svm_guest_mode.  */
>  		if (!test_bit(VCPU_EXREG_CR3, (ulong *)&vcpu->arch.regs_avail))
>  			return;
> diff --git a/arch/x86/kvm/svm/svm_onhyperv.h b/arch/x86/kvm/svm/svm_onhyperv.h
> new file mode 100644
> index 000000000000..57291e222395
> --- /dev/null
> +++ b/arch/x86/kvm/svm/svm_onhyperv.h
> @@ -0,0 +1,66 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * KVM L1 hypervisor optimizations on Hyper-V for SVM.
> + */
> +
> +#ifndef __ARCH_X86_KVM_SVM_ONHYPERV_H__
> +#define __ARCH_X86_KVM_SVM_ONHYPERV_H__
> +
> +#if IS_ENABLED(CONFIG_HYPERV)
> +#include <asm/mshyperv.h>
> +
> +#include "hyperv.h"
> +#include "kvm_onhyperv.h"
> +
> +static struct kvm_x86_ops svm_x86_ops;
> +
> +/*
> + * Hyper-V uses the software reserved 32 bytes in VMCB
> + * control area to expose SVM enlightenments to guests.
> + */
> +struct hv_enlightenments {
> +	struct __packed hv_enlightenments_control {
> +		u32 nested_flush_hypercall:1;
> +		u32 msr_bitmap:1;
> +		u32 enlightened_npt_tlb: 1;
> +		u32 reserved:29;
> +	} __packed hv_enlightenments_control;
> +	u32 hv_vp_id;
> +	u64 hv_vm_id;
> +	u64 partition_assist_page;
> +	u64 reserved;
> +} __packed;
> +
> +static inline void svm_hv_init_vmcb(struct vmcb *vmcb)
> +{
> +	struct hv_enlightenments *hve =
> +		(struct hv_enlightenments *)vmcb->control.reserved_sw;

Perhaps add a "BUILD_BUG_ON" to verify that struct
hv_enlightenments fits in the space allocated for
vmcb->control.reserved_sw?

> +
> +	if (npt_enabled &&
> +	    ms_hyperv.nested_features & HV_X64_NESTED_ENLIGHTENED_TLB)
> +		hve->hv_enlightenments_control.enlightened_npt_tlb = 1;
> +}
> +
> +static inline void svm_hv_hardware_setup(void)
> +{
> +	if (npt_enabled &&
> +	    ms_hyperv.nested_features & HV_X64_NESTED_ENLIGHTENED_TLB) {
> +		pr_info("kvm: Hyper-V enlightened NPT TLB flush enabled\n");
> +		svm_x86_ops.tlb_remote_flush = hv_remote_flush_tlb;
> +		svm_x86_ops.tlb_remote_flush_with_range =
> +				hv_remote_flush_tlb_with_range;
> +	}
> +}
> +
> +#else
> +
> +static inline void svm_hv_init_vmcb(struct vmcb *vmcb)
> +{
> +}
> +
> +static inline void svm_hv_hardware_setup(void)
> +{
> +}
> +#endif /* CONFIG_HYPERV */
> +
> +#endif /* __ARCH_X86_KVM_SVM_ONHYPERV_H__ */
> --
> 2.25.1