Re: [Xen-devel] [PATCH] nvmx: fix resource relinquish for nested VMX

[Keir Fraser <keir@xxxxxxx>]

On 23/08/2012 04:11, "Dongxiao Xu" <dongxiao.xu@xxxxxxxxx> wrote:

> The previous order of relinquish resource is:
> relinquish_domain_resources() -> vcpu_destroy() -> nvmx_vcpu_destroy().
> However some L1 resources like nv_vvmcx and io_bitmaps are free in
> nvmx_vcpu_destroy(), therefore the relinquish_domain_resources()
> will not reduce the refcnt of the domain to 0, therefore the latter
> vcpu release functions will not be called.
> 
> To fix this issue, we need to release the nv_vvmcx and io_bitmaps in
> relinquish_domain_resources().
> 
> Besides, after destroy the nested vcpu, we need to switch the vmx->vmcs
> back to the L1 and let the vcpu_destroy() logic to free the L1 VMCS page.
> 
> Signed-off-by: Dongxiao Xu <dongxiao.xu@xxxxxxxxx>

Couple of comments below.

> diff --git a/xen/arch/x86/hvm/vmx/vvmx.c b/xen/arch/x86/hvm/vmx/vvmx.c
> index 2e0b79d..1f610eb 100644
> --- a/xen/arch/x86/hvm/vmx/vvmx.c
> +++ b/xen/arch/x86/hvm/vmx/vvmx.c
> @@ -57,6 +57,9 @@ void nvmx_vcpu_destroy(struct vcpu *v)
>  {
>      struct nestedvcpu *nvcpu = &vcpu_nestedhvm(v);
>  
> +    if ( nvcpu->nv_n1vmcx )
> +        v->arch.hvm_vmx.vmcs = nvcpu->nv_n1vmcx;

Okay, this undoes the fork in nvmx_handle_vmxon()? A small code comment to
explain that would be handy.

>      nvmx_purge_vvmcs(v);

This call of nvmx_purge_vvmcs() is no longer needed, and should be removed?

 -- Keir

>      if ( nvcpu->nv_n2vmcx ) {
>          __vmpclear(virt_to_maddr(nvcpu->nv_n2vmcx));
> @@ -65,6 +68,14 @@ void nvmx_vcpu_destroy(struct vcpu *v)
>      }
>  }
>   
> +void nvmx_domain_relinquish_resources(struct domain *d)
> +{
> +    struct vcpu *v;
> +
> +    for_each_vcpu ( d, v )
> +        nvmx_purge_vvmcs(v);
> +}
> +
>  int nvmx_vcpu_reset(struct vcpu *v)
>  {
>      return 0;
> diff --git a/xen/include/asm-x86/hvm/hvm.h b/xen/include/asm-x86/hvm/hvm.h
> index 7243c4e..3592a8c 100644
> --- a/xen/include/asm-x86/hvm/hvm.h
> +++ b/xen/include/asm-x86/hvm/hvm.h
> @@ -179,6 +179,7 @@ struct hvm_function_table {
>      bool_t (*nhvm_vmcx_hap_enabled)(struct vcpu *v);
>  
>      enum hvm_intblk (*nhvm_intr_blocked)(struct vcpu *v);
> +    void (*nhvm_domain_relinquish_resources)(struct domain *d);
>  };
>  
>  extern struct hvm_function_table hvm_funcs;
> diff --git a/xen/include/asm-x86/hvm/vmx/vvmx.h
> b/xen/include/asm-x86/hvm/vmx/vvmx.h
> index 995f9f4..bbc34e7 100644
> --- a/xen/include/asm-x86/hvm/vmx/vvmx.h
> +++ b/xen/include/asm-x86/hvm/vmx/vvmx.h
> @@ -96,6 +96,7 @@ uint32_t nvmx_vcpu_asid(struct vcpu *v);
>  enum hvm_intblk nvmx_intr_blocked(struct vcpu *v);
>  int nvmx_intercepts_exception(struct vcpu *v,
>                                unsigned int trap, int error_code);
> +void nvmx_domain_relinquish_resources(struct domain *d);
>  
>  int nvmx_handle_vmxon(struct cpu_user_regs *regs);
>  int nvmx_handle_vmxoff(struct cpu_user_regs *regs);



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