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* Re: [PATCH 5/5] KVM: nVMX: optimize prepare_vmcs02{,_full} for Enlightened VMCS case
@ 2018-06-14 23:37 Liran Alon
  2018-06-15 10:31 ` Vitaly Kuznetsov
  0 siblings, 1 reply; 3+ messages in thread
From: Liran Alon @ 2018-06-14 23:37 UTC (permalink / raw)
  To: vkuznets
  Cc: mmorsy, rkagan, jmattson, Michael.H.Kelley, kys, rkrcmar, cavery,
	pbonzini, linux-kernel, sthemmin, haiyangz, kvm


----- vkuznets@redhat.com wrote:

> When Enlightened VMCS is in use by L1 hypervisor we can avoid
> vmwriting
> VMCS fields which did not change.
> 
> Our first goal is to achieve minimal impact on traditional VMCS case
> so
> we're not wrapping each vmwrite() with an if-changed checker. We also
> can't
> utilize static keys as Enlightened VMCS usage is per-guest.
> 
> This patch implements the simpliest solution: checking fields in
> groups.
> We skip single vmwrite() statements as doing the check will cost us
> something even in non-evmcs case and the win is tiny. Unfortunately,
> this
> makes prepare_vmcs02_full{,_full}() code Enlightened VMCS-dependent
> (and
> a bit ugly).
> 
> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> ---
>  arch/x86/kvm/vmx.c | 143
> ++++++++++++++++++++++++++++++-----------------------
>  1 file changed, 82 insertions(+), 61 deletions(-)
> 
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 6802ba91468c..9a7d76c5c92b 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -11619,50 +11619,79 @@ static int nested_vmx_load_cr3(struct
> kvm_vcpu *vcpu, unsigned long cr3, bool ne
>  	return 0;
>  }
>  
> +/*
> + * Check if L1 hypervisor changed the particular field in
> Enlightened
> + * VMCS and avoid redundant vmwrite if it didn't. Can only be used
> when
> + * the value we're about to write is unchanged vmcs12->field.
> + */
> +#define evmcs_needs_write(vmx, clean_field)
> ((vmx)->nested.dirty_vmcs12 ||\
> +	!(vmx->nested.hv_evmcs->hv_clean_fields &\
> +	  HV_VMX_ENLIGHTENED_CLEAN_FIELD_##clean_field))

Why declare this is a macro instead of an static inline small function?
Just to shorten the name of the clean-field constant?

> +
>  static void prepare_vmcs02_full(struct kvm_vcpu *vcpu, struct vmcs12
> *vmcs12)
>  {
>  	struct vcpu_vmx *vmx = to_vmx(vcpu);
> +	struct hv_enlightened_vmcs *hv_evmcs = vmx->nested.hv_evmcs;
> +
> +	if (!hv_evmcs || evmcs_needs_write(vmx, GUEST_GRP2)) {
> +		vmcs_write16(GUEST_ES_SELECTOR, vmcs12->guest_es_selector);
> +		vmcs_write16(GUEST_SS_SELECTOR, vmcs12->guest_ss_selector);
> +		vmcs_write16(GUEST_DS_SELECTOR, vmcs12->guest_ds_selector);
> +		vmcs_write16(GUEST_FS_SELECTOR, vmcs12->guest_fs_selector);
> +		vmcs_write16(GUEST_GS_SELECTOR, vmcs12->guest_gs_selector);
> +		vmcs_write16(GUEST_LDTR_SELECTOR, vmcs12->guest_ldtr_selector);
> +		vmcs_write16(GUEST_TR_SELECTOR, vmcs12->guest_tr_selector);
> +		vmcs_write32(GUEST_ES_LIMIT, vmcs12->guest_es_limit);
> +		vmcs_write32(GUEST_SS_LIMIT, vmcs12->guest_ss_limit);
> +		vmcs_write32(GUEST_DS_LIMIT, vmcs12->guest_ds_limit);
> +		vmcs_write32(GUEST_FS_LIMIT, vmcs12->guest_fs_limit);
> +		vmcs_write32(GUEST_GS_LIMIT, vmcs12->guest_gs_limit);
> +		vmcs_write32(GUEST_LDTR_LIMIT, vmcs12->guest_ldtr_limit);
> +		vmcs_write32(GUEST_TR_LIMIT, vmcs12->guest_tr_limit);
> +		vmcs_write32(GUEST_GDTR_LIMIT, vmcs12->guest_gdtr_limit);
> +		vmcs_write32(GUEST_IDTR_LIMIT, vmcs12->guest_idtr_limit);
> +		vmcs_write32(GUEST_ES_AR_BYTES, vmcs12->guest_es_ar_bytes);
> +		vmcs_write32(GUEST_SS_AR_BYTES, vmcs12->guest_ss_ar_bytes);
> +		vmcs_write32(GUEST_DS_AR_BYTES, vmcs12->guest_ds_ar_bytes);
> +		vmcs_write32(GUEST_FS_AR_BYTES, vmcs12->guest_fs_ar_bytes);
> +		vmcs_write32(GUEST_GS_AR_BYTES, vmcs12->guest_gs_ar_bytes);
> +		vmcs_write32(GUEST_LDTR_AR_BYTES, vmcs12->guest_ldtr_ar_bytes);
> +		vmcs_write32(GUEST_TR_AR_BYTES, vmcs12->guest_tr_ar_bytes);
> +		vmcs_writel(GUEST_SS_BASE, vmcs12->guest_ss_base);
> +		vmcs_writel(GUEST_DS_BASE, vmcs12->guest_ds_base);
> +		vmcs_writel(GUEST_FS_BASE, vmcs12->guest_fs_base);
> +		vmcs_writel(GUEST_GS_BASE, vmcs12->guest_gs_base);
> +		vmcs_writel(GUEST_LDTR_BASE, vmcs12->guest_ldtr_base);
> +		vmcs_writel(GUEST_TR_BASE, vmcs12->guest_tr_base);
> +		vmcs_writel(GUEST_GDTR_BASE, vmcs12->guest_gdtr_base);
> +		vmcs_writel(GUEST_IDTR_BASE, vmcs12->guest_idtr_base);
> +	}
> +
> +	if (!hv_evmcs || evmcs_needs_write(vmx, GUEST_GRP1)) {
> +		vmcs_write32(GUEST_SYSENTER_CS, vmcs12->guest_sysenter_cs);
> +		vmcs_writel(GUEST_PENDING_DBG_EXCEPTIONS,
> +			    vmcs12->guest_pending_dbg_exceptions);
> +		vmcs_writel(GUEST_SYSENTER_ESP, vmcs12->guest_sysenter_esp);
> +		vmcs_writel(GUEST_SYSENTER_EIP, vmcs12->guest_sysenter_eip);
> +
> +		if (vmx_mpx_supported())
> +			vmcs_write64(GUEST_BNDCFGS, vmcs12->guest_bndcfgs);
>  
> -	vmcs_write16(GUEST_ES_SELECTOR, vmcs12->guest_es_selector);
> -	vmcs_write16(GUEST_SS_SELECTOR, vmcs12->guest_ss_selector);
> -	vmcs_write16(GUEST_DS_SELECTOR, vmcs12->guest_ds_selector);
> -	vmcs_write16(GUEST_FS_SELECTOR, vmcs12->guest_fs_selector);
> -	vmcs_write16(GUEST_GS_SELECTOR, vmcs12->guest_gs_selector);
> -	vmcs_write16(GUEST_LDTR_SELECTOR, vmcs12->guest_ldtr_selector);
> -	vmcs_write16(GUEST_TR_SELECTOR, vmcs12->guest_tr_selector);
> -	vmcs_write32(GUEST_ES_LIMIT, vmcs12->guest_es_limit);
> -	vmcs_write32(GUEST_SS_LIMIT, vmcs12->guest_ss_limit);
> -	vmcs_write32(GUEST_DS_LIMIT, vmcs12->guest_ds_limit);
> -	vmcs_write32(GUEST_FS_LIMIT, vmcs12->guest_fs_limit);
> -	vmcs_write32(GUEST_GS_LIMIT, vmcs12->guest_gs_limit);
> -	vmcs_write32(GUEST_LDTR_LIMIT, vmcs12->guest_ldtr_limit);
> -	vmcs_write32(GUEST_TR_LIMIT, vmcs12->guest_tr_limit);
> -	vmcs_write32(GUEST_GDTR_LIMIT, vmcs12->guest_gdtr_limit);
> -	vmcs_write32(GUEST_IDTR_LIMIT, vmcs12->guest_idtr_limit);
> -	vmcs_write32(GUEST_ES_AR_BYTES, vmcs12->guest_es_ar_bytes);
> -	vmcs_write32(GUEST_SS_AR_BYTES, vmcs12->guest_ss_ar_bytes);
> -	vmcs_write32(GUEST_DS_AR_BYTES, vmcs12->guest_ds_ar_bytes);
> -	vmcs_write32(GUEST_FS_AR_BYTES, vmcs12->guest_fs_ar_bytes);
> -	vmcs_write32(GUEST_GS_AR_BYTES, vmcs12->guest_gs_ar_bytes);
> -	vmcs_write32(GUEST_LDTR_AR_BYTES, vmcs12->guest_ldtr_ar_bytes);
> -	vmcs_write32(GUEST_TR_AR_BYTES, vmcs12->guest_tr_ar_bytes);
> -	vmcs_writel(GUEST_SS_BASE, vmcs12->guest_ss_base);
> -	vmcs_writel(GUEST_DS_BASE, vmcs12->guest_ds_base);
> -	vmcs_writel(GUEST_FS_BASE, vmcs12->guest_fs_base);
> -	vmcs_writel(GUEST_GS_BASE, vmcs12->guest_gs_base);
> -	vmcs_writel(GUEST_LDTR_BASE, vmcs12->guest_ldtr_base);
> -	vmcs_writel(GUEST_TR_BASE, vmcs12->guest_tr_base);
> -	vmcs_writel(GUEST_GDTR_BASE, vmcs12->guest_gdtr_base);
> -	vmcs_writel(GUEST_IDTR_BASE, vmcs12->guest_idtr_base);
> -
> -	vmcs_write32(GUEST_SYSENTER_CS, vmcs12->guest_sysenter_cs);
> -	vmcs_writel(GUEST_PENDING_DBG_EXCEPTIONS,
> -		vmcs12->guest_pending_dbg_exceptions);
> -	vmcs_writel(GUEST_SYSENTER_ESP, vmcs12->guest_sysenter_esp);
> -	vmcs_writel(GUEST_SYSENTER_EIP, vmcs12->guest_sysenter_eip);
> +		/*
> +		 * L1 may access the L2's PDPTR, so save them to construct
> +		 * vmcs12
> +		 */
> +		if (enable_ept) {
> +			vmcs_write64(GUEST_PDPTR0, vmcs12->guest_pdptr0);
> +			vmcs_write64(GUEST_PDPTR1, vmcs12->guest_pdptr1);
> +			vmcs_write64(GUEST_PDPTR2, vmcs12->guest_pdptr2);
> +			vmcs_write64(GUEST_PDPTR3, vmcs12->guest_pdptr3);
> +		}
> +	}
>  
>  	if (nested_cpu_has_xsaves(vmcs12))
>  		vmcs_write64(XSS_EXIT_BITMAP, vmcs12->xss_exit_bitmap);
> +
>  	vmcs_write64(VMCS_LINK_POINTER, -1ull);
>  
>  	if (cpu_has_vmx_posted_intr())
> @@ -11717,9 +11746,6 @@ static void prepare_vmcs02_full(struct
> kvm_vcpu *vcpu, struct vmcs12 *vmcs12)
>  
>  	set_cr4_guest_host_mask(vmx);
>  
> -	if (vmx_mpx_supported())
> -		vmcs_write64(GUEST_BNDCFGS, vmcs12->guest_bndcfgs);
> -
>  	if (enable_vpid) {
>  		if (nested_cpu_has_vpid(vmcs12) && vmx->nested.vpid02)
>  			vmcs_write16(VIRTUAL_PROCESSOR_ID, vmx->nested.vpid02);
> @@ -11727,16 +11753,6 @@ static void prepare_vmcs02_full(struct
> kvm_vcpu *vcpu, struct vmcs12 *vmcs12)
>  			vmcs_write16(VIRTUAL_PROCESSOR_ID, vmx->vpid);
>  	}
>  
> -	/*
> -	 * L1 may access the L2's PDPTR, so save them to construct vmcs12
> -	 */
> -	if (enable_ept) {
> -		vmcs_write64(GUEST_PDPTR0, vmcs12->guest_pdptr0);
> -		vmcs_write64(GUEST_PDPTR1, vmcs12->guest_pdptr1);
> -		vmcs_write64(GUEST_PDPTR2, vmcs12->guest_pdptr2);
> -		vmcs_write64(GUEST_PDPTR3, vmcs12->guest_pdptr3);
> -	}
> -
>  	if (cpu_has_vmx_msr_bitmap())
>  		vmcs_write64(MSR_BITMAP, __pa(vmx->nested.vmcs02.msr_bitmap));
>  }
> @@ -11757,6 +11773,7 @@ static int prepare_vmcs02(struct kvm_vcpu
> *vcpu, struct vmcs12 *vmcs12,
>  {
>  	struct vcpu_vmx *vmx = to_vmx(vcpu);
>  	u32 exec_control, vmcs12_exec_ctrl;
> +	struct hv_enlightened_vmcs *hv_evmcs = vmx->nested.hv_evmcs;
>  
>  	if (vmx->nested.dirty_vmcs12 || vmx->nested.hv_evmcs) {
>  		prepare_vmcs02_full(vcpu, vmcs12);
> @@ -11768,11 +11785,13 @@ static int prepare_vmcs02(struct kvm_vcpu
> *vcpu, struct vmcs12 *vmcs12,
>  	 * with vmx_shadow_fields.h.
>  	 */
>  
> -	vmcs_write16(GUEST_CS_SELECTOR, vmcs12->guest_cs_selector);
> -	vmcs_write32(GUEST_CS_LIMIT, vmcs12->guest_cs_limit);
> -	vmcs_write32(GUEST_CS_AR_BYTES, vmcs12->guest_cs_ar_bytes);
> -	vmcs_writel(GUEST_ES_BASE, vmcs12->guest_es_base);
> -	vmcs_writel(GUEST_CS_BASE, vmcs12->guest_cs_base);
> +	if (!hv_evmcs || evmcs_needs_write(vmx, GUEST_GRP2)) {
> +		vmcs_write16(GUEST_CS_SELECTOR, vmcs12->guest_cs_selector);
> +		vmcs_write32(GUEST_CS_LIMIT, vmcs12->guest_cs_limit);
> +		vmcs_write32(GUEST_CS_AR_BYTES, vmcs12->guest_cs_ar_bytes);
> +		vmcs_writel(GUEST_ES_BASE, vmcs12->guest_es_base);
> +		vmcs_writel(GUEST_CS_BASE, vmcs12->guest_cs_base);
> +	}
>  
>  	/*
>  	 * Not in vmcs02: GUEST_PML_INDEX, HOST_FS_SELECTOR,
> HOST_GS_SELECTOR,
> @@ -11788,12 +11807,14 @@ static int prepare_vmcs02(struct kvm_vcpu
> *vcpu, struct vmcs12 *vmcs12,
>  		vmcs_write64(GUEST_IA32_DEBUGCTL, vmx->nested.vmcs01_debugctl);
>  	}
>  	if (vmx->nested.nested_run_pending) {
> -		vmcs_write32(VM_ENTRY_INTR_INFO_FIELD,
> -			     vmcs12->vm_entry_intr_info_field);
> -		vmcs_write32(VM_ENTRY_EXCEPTION_ERROR_CODE,
> -			     vmcs12->vm_entry_exception_error_code);
> -		vmcs_write32(VM_ENTRY_INSTRUCTION_LEN,
> -			     vmcs12->vm_entry_instruction_len);
> +		if (!hv_evmcs || evmcs_needs_write(vmx, CONTROL_EVENT)) {
> +			vmcs_write32(VM_ENTRY_INTR_INFO_FIELD,
> +				     vmcs12->vm_entry_intr_info_field);
> +			vmcs_write32(VM_ENTRY_EXCEPTION_ERROR_CODE,
> +				     vmcs12->vm_entry_exception_error_code);
> +			vmcs_write32(VM_ENTRY_INSTRUCTION_LEN,
> +				     vmcs12->vm_entry_instruction_len);
> +		}
>  		vmcs_write32(GUEST_INTERRUPTIBILITY_INFO,
>  			     vmcs12->guest_interruptibility_info);
>  		vmx->loaded_vmcs->nmi_known_unmasked =
> -- 
> 2.14.4

^ permalink raw reply	[flat|nested] 3+ messages in thread
* [PATCH 0/5] KVM: nVMX: Enlightened VMCS for Hyper-V on KVM
@ 2018-06-14  8:24 Vitaly Kuznetsov
  2018-06-14  8:25 ` [PATCH 5/5] KVM: nVMX: optimize prepare_vmcs02{,_full} for Enlightened VMCS case Vitaly Kuznetsov
  0 siblings, 1 reply; 3+ messages in thread
From: Vitaly Kuznetsov @ 2018-06-14  8:24 UTC (permalink / raw)
  To: kvm
  Cc: Paolo Bonzini, Radim Krčmář, Roman Kagan,
	K. Y. Srinivasan, Haiyang Zhang, Stephen Hemminger,
	Michael Kelley (EOSG), Mohammed Gamal, Cathy Avery, linux-kernel,
	Jim Mattson

This is an initial implementation of Enlightened VMCS for nested Hyper-V on
KVM. Using it helps to spare 1500 cpu cycles for nested vmexit (tight cpuid
loop in WS2016 with Hyper-V role on KVM: 15200 cycles -> 13700 cycles).

Changes since RFCv2:
- Rename sync_shadow_vmcs to need_vmcs12_sync and reuse for eVMCS case
  [Paolo Bonzini]

Ladi Prosek (1):
  KVM: hyperv: define VP assist page helpers

Vitaly Kuznetsov (4):
  KVM: nVMX: add KVM_CAP_HYPERV_ENLIGHTENED_VMCS capability
  KVM: nVMX: add enlightened VMCS state
  KVM: nVMX: implement enlightened VMPTRLD and VMCLEAR
  KVM: nVMX: optimize prepare_vmcs02{,_full} for Enlightened VMCS case

 arch/x86/include/asm/kvm_host.h |   3 +
 arch/x86/kvm/hyperv.c           |  23 +-
 arch/x86/kvm/hyperv.h           |   4 +
 arch/x86/kvm/lapic.c            |   4 +-
 arch/x86/kvm/lapic.h            |   2 +-
 arch/x86/kvm/svm.c              |   9 +
 arch/x86/kvm/vmx.c              | 810 +++++++++++++++++++++++++++++++++-------
 arch/x86/kvm/x86.c              |  17 +-
 include/uapi/linux/kvm.h        |   1 +
 9 files changed, 724 insertions(+), 149 deletions(-)

-- 
2.14.4


^ permalink raw reply	[flat|nested] 3+ messages in thread
end of thread, other threads:[~2018-06-15 10:31 UTC | newest]

Thread overview: 3+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2018-06-14 23:37 [PATCH 5/5] KVM: nVMX: optimize prepare_vmcs02{,_full} for Enlightened VMCS case Liran Alon
2018-06-15 10:31 ` Vitaly Kuznetsov
  -- strict thread matches above, loose matches on Subject: below --
2018-06-14  8:24 [PATCH 0/5] KVM: nVMX: Enlightened VMCS for Hyper-V on KVM Vitaly Kuznetsov
2018-06-14  8:25 ` [PATCH 5/5] KVM: nVMX: optimize prepare_vmcs02{,_full} for Enlightened VMCS case Vitaly Kuznetsov

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