linux-kernel - Re: [PATCH 3.10 19/24] nEPT: Nested INVEPT

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Date:	Mon, 15 Dec 2014 10:32:38 +0100
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-kernel@...r.kernel.org
CC:	stable@...r.kernel.org,
	Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>,
	Nadav HarEl <nyh@...ibm.com>,
	Jun Nakajima <jun.nakajima@...el.com>,
	Xinhao Xu <xinhao.xu@...el.com>,
	Yang Zhang <yang.z.zhang@...el.com>,
	Gleb Natapov <gleb@...hat.com>,
	Ben Hutchings <ben@...adent.org.uk>,
	Vinson Lee <vlee@...pensource.com>
Subject: Re: [PATCH 3.10 19/24] nEPT: Nested INVEPT



On 14/12/2014 21:20, Greg Kroah-Hartman wrote:
> 3.10-stable review patch.  If anyone has any objections, please let me know.
> 
> ------------------
> 
> From: Nadav Har'El <nyh@...ibm.com>
> 
> commit bfd0a56b90005f8c8a004baf407ad90045c2b11e upstream.
> 
> If we let L1 use EPT, we should probably also support the INVEPT instruction.
> 
> In our current nested EPT implementation, when L1 changes its EPT table
> for L2 (i.e., EPT12), L0 modifies the shadow EPT table (EPT02), and in
> the course of this modification already calls INVEPT. But if last level
> of shadow page is unsync not all L1's changes to EPT12 are intercepted,
> which means roots need to be synced when L1 calls INVEPT. Global INVEPT
> should not be different since roots are synced by kvm_mmu_load() each
> time EPTP02 changes.
> 
> Reviewed-by: Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
> Signed-off-by: Nadav Har'El <nyh@...ibm.com>
> Signed-off-by: Jun Nakajima <jun.nakajima@...el.com>
> Signed-off-by: Xinhao Xu <xinhao.xu@...el.com>
> Signed-off-by: Yang Zhang <yang.z.zhang@...el.com>
> Signed-off-by: Gleb Natapov <gleb@...hat.com>
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
> [bwh: Backported to 3.2:
>  - Adjust context, filename
>  - Simplify handle_invept() as recommended by Paolo - nEPT is not
>    supported so we always raise #UD]
> Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
> Cc: Vinson Lee <vlee@...pensource.com>
> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> 
> ---
>  arch/x86/include/uapi/asm/vmx.h |    1 +
>  arch/x86/kvm/vmx.c              |    8 ++++++++
>  2 files changed, 9 insertions(+)
> 
> --- a/arch/x86/include/uapi/asm/vmx.h
> +++ b/arch/x86/include/uapi/asm/vmx.h
> @@ -65,6 +65,7 @@
>  #define EXIT_REASON_EOI_INDUCED         45
>  #define EXIT_REASON_EPT_VIOLATION       48
>  #define EXIT_REASON_EPT_MISCONFIG       49
> +#define EXIT_REASON_INVEPT              50
>  #define EXIT_REASON_PREEMPTION_TIMER    52
>  #define EXIT_REASON_WBINVD              54
>  #define EXIT_REASON_XSETBV              55
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -6242,6 +6242,12 @@ static int handle_vmptrst(struct kvm_vcp
>  	return 1;
>  }
>  
> +static int handle_invept(struct kvm_vcpu *vcpu)
> +{
> +	kvm_queue_exception(vcpu, UD_VECTOR);
> +	return 1;
> +}
> +
>  /*
>   * The exit handlers return 1 if the exit was handled fully and guest execution
>   * may resume.  Otherwise they set the kvm_run parameter to indicate what needs
> @@ -6286,6 +6292,7 @@ static int (*const kvm_vmx_exit_handlers
>  	[EXIT_REASON_PAUSE_INSTRUCTION]       = handle_pause,
>  	[EXIT_REASON_MWAIT_INSTRUCTION]	      = handle_invalid_op,
>  	[EXIT_REASON_MONITOR_INSTRUCTION]     = handle_invalid_op,
> +	[EXIT_REASON_INVEPT]                  = handle_invept,
>  };
>  
>  static const int kvm_vmx_max_exit_handlers =
> @@ -6512,6 +6519,7 @@ static bool nested_vmx_exit_handled(stru
>  	case EXIT_REASON_VMPTRST: case EXIT_REASON_VMREAD:
>  	case EXIT_REASON_VMRESUME: case EXIT_REASON_VMWRITE:
>  	case EXIT_REASON_VMOFF: case EXIT_REASON_VMON:
> +	case EXIT_REASON_INVEPT:
>  		/*
>  		 * VMX instructions trap unconditionally. This allows L1 to
>  		 * emulate them for its L2 guest, i.e., allows 3-level nesting!
> 
> 

Reviewed-by: Paolo Bonzini <pbonzini@...hat.com>

Thanks Greg.

Paolo
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