Re: [PATCH 09/10] KVM: nVMX: Synchronize VMCS12 content with the shadow vmcs

[Gleb Natapov <gleb@redhat.com>]

On Wed, Apr 17, 2013 at 02:55:10PM +0300, Abel Gordon wrote:
> Synchronize between the VMCS12 software controlled structure and the
> processor-specific shadow vmcs
> 
> Signed-off-by: Abel Gordon <abelg@il.ibm.com>
> ---
>  arch/x86/kvm/vmx.c |   24 ++++++++++++++++++++++++
>  1 file changed, 24 insertions(+)
> 
> --- .before/arch/x86/kvm/vmx.c	2013-04-17 14:20:51.000000000 +0300
> +++ .after/arch/x86/kvm/vmx.c	2013-04-17 14:20:51.000000000 +0300
> @@ -356,6 +356,11 @@ struct nested_vmx {
>  	struct page *current_vmcs12_page;
>  	struct vmcs12 *current_vmcs12;
>  	struct vmcs *current_shadow_vmcs;
> +	/*
> +	 * Indicates if the shadow vmcs must be updated with the
> +	 * data hold by vmcs12
> +	 */
> +	bool sync_shadow_vmcs;
>  
>  	/* vmcs02_list cache of VMCSs recently used to run L2 guests */
>  	struct list_head vmcs02_pool;
> @@ -5587,6 +5592,10 @@ static inline void nested_release_vmcs12
>  {
>  	if (enable_shadow_vmcs) {
>  		if (vmx->nested.current_vmcs12 != NULL) {
> +			/* copy to memory all shadowed fields in case
> +			   they were modified */
> +			copy_shadow_to_vmcs12(vmx);
> +			vmx->nested.sync_shadow_vmcs = false;
>  			free_vmcs(vmx->nested.current_shadow_vmcs);
>  		}
>  	}
> @@ -5716,6 +5725,10 @@ static void nested_vmx_failValid(struct 
>  			    X86_EFLAGS_SF | X86_EFLAGS_OF))
>  			| X86_EFLAGS_ZF);
>  	get_vmcs12(vcpu)->vm_instruction_error = vm_instruction_error;
> +	/*
> +	 * We don't need to force a shadow sync because
> +	 * VM_INSTRUCTION_ERROR is not shdowed
---------------------------------------^ shadowed.
But lets just request sync. This is slow path anyway.

> +	 */
>  }
>  
>  /* Emulate the VMCLEAR instruction */
> @@ -6127,6 +6140,7 @@ static int handle_vmptrld(struct kvm_vcp
>  			/* init shadow vmcs */
>  			vmcs_clear(shadow_vmcs);
>  			vmx->nested.current_shadow_vmcs = shadow_vmcs;
> +			vmx->nested.sync_shadow_vmcs = true;
>  		}
>  	}
>  
> @@ -6876,6 +6890,10 @@ static void __noclone vmx_vcpu_run(struc
>  {
>  	struct vcpu_vmx *vmx = to_vmx(vcpu);
>  	unsigned long debugctlmsr;
Leave free line here and move it after if(vmx->emulation_required).

> +	if (vmx->nested.sync_shadow_vmcs) {
> +		copy_vmcs12_to_shadow(vmx);
> +		vmx->nested.sync_shadow_vmcs = false;
> +	}
>  
>  	/* Record the guest's net vcpu time for enforced NMI injections. */
>  	if (unlikely(!cpu_has_virtual_nmis() && vmx->soft_vnmi_blocked))
> @@ -7496,6 +7514,8 @@ static int nested_vmx_run(struct kvm_vcp
>  	skip_emulated_instruction(vcpu);
>  	vmcs12 = get_vmcs12(vcpu);
>  
> +	if (enable_shadow_vmcs)
> +		copy_shadow_to_vmcs12(vmx);
And free line here.

>  	/*
>  	 * The nested entry process starts with enforcing various prerequisites
>  	 * on vmcs12 as required by the Intel SDM, and act appropriately when
> @@ -7938,6 +7958,8 @@ static void nested_vmx_vmexit(struct kvm
>  		nested_vmx_failValid(vcpu, vmcs_read32(VM_INSTRUCTION_ERROR));
>  	} else
>  		nested_vmx_succeed(vcpu);
> +	if (enable_shadow_vmcs)
> +		vmx->nested.sync_shadow_vmcs = true;
>  }
>  
>  /*
> @@ -7955,6 +7977,8 @@ static void nested_vmx_entry_failure(str
>  	vmcs12->vm_exit_reason = reason | VMX_EXIT_REASONS_FAILED_VMENTRY;
>  	vmcs12->exit_qualification = qualification;
>  	nested_vmx_succeed(vcpu);
> +	if (enable_shadow_vmcs)
> +		to_vmx(vcpu)->nested.sync_shadow_vmcs = true;
>  }
>  
>  static int vmx_check_intercept(struct kvm_vcpu *vcpu,
> 
> --
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--
			Gleb.