linux-kernel - Re: [PATCH v2 3/5] KVM: nVMX: emulate the INVVPID instruction

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Date:	Tue, 13 Oct 2015 16:35:09 +0200
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Wanpeng Li <wanpeng.li@...mail.com>
Cc:	Jan Kiszka <jan.kiszka@...mens.com>, Bandan Das <bsd@...hat.com>,
	Wincy Van <fanwenyi0529@...il.com>, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/5] KVM: nVMX: emulate the INVVPID instruction



On 08/10/2015 07:57, Wanpeng Li wrote:
> Add the INVVPID instruction emulation.
> 
> Reviewed-by: Wincy Van <fanwenyi0529@...il.com>
> Signed-off-by: Wanpeng Li <wanpeng.li@...mail.com>
> ---
>  arch/x86/include/asm/vmx.h |  3 +++
>  arch/x86/kvm/vmx.c         | 49 +++++++++++++++++++++++++++++++++++++++++++++-
>  2 files changed, 51 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/include/asm/vmx.h b/arch/x86/include/asm/vmx.h
> index 448b7ca..af5fdaf 100644
> --- a/arch/x86/include/asm/vmx.h
> +++ b/arch/x86/include/asm/vmx.h
> @@ -397,8 +397,10 @@ enum vmcs_field {
>  #define IDENTITY_PAGETABLE_PRIVATE_MEMSLOT	(KVM_USER_MEM_SLOTS + 2)
>  
>  #define VMX_NR_VPIDS				(1 << 16)
> +#define VMX_VPID_EXTENT_INDIVIDUAL_ADDR 	0
>  #define VMX_VPID_EXTENT_SINGLE_CONTEXT		1
>  #define VMX_VPID_EXTENT_ALL_CONTEXT		2
> +#define VMX_VPID_EXTENT_SHIFT			40

This is not used.

Comparing handle_invept with handle_invvpid, some differences are 
apparent:

>  static int handle_invvpid(struct kvm_vcpu *vcpu)
>  {
> -	kvm_queue_exception(vcpu, UD_VECTOR);
> +	struct vcpu_vmx *vmx = to_vmx(vcpu);
> +	u32 vmx_instruction_info;
> +	unsigned long type;
> +	gva_t gva;
> +	struct x86_exception e;
> +	int vpid;
> +
> +	if (!(vmx->nested.nested_vmx_secondary_ctls_high &
> +	      SECONDARY_EXEC_ENABLE_VPID)) {

This lacks a check against VMX_VPID_INVVPID_BIT.

> +		kvm_queue_exception(vcpu, UD_VECTOR);
> +		return 1;
> +	}
> +
> +	if (!nested_vmx_check_permission(vcpu))
> +		return 1;
> +
> +	vmx_instruction_info = vmcs_read32(VMX_INSTRUCTION_INFO);
> +	type = kvm_register_readl(vcpu, (vmx_instruction_info >> 28) & 0xf);

This is missing the equivalent of this invept code:

        types = (vmx->nested.nested_vmx_ept_caps >> VMX_EPT_EXTENT_SHIFT) & 6;

        if (!(types & (1UL << type))) {
                nested_vmx_failValid(vcpu,
                                VMXERR_INVALID_OPERAND_TO_INVEPT_INVVPID);
                return 1;
        }

> +	/* according to the intel vmx instruction reference, the memory
> +	 * operand is read even if it isn't needed (e.g., for type==global)
> +	 */
> +	if (get_vmx_mem_address(vcpu, vmcs_readl(EXIT_QUALIFICATION),
> +			vmx_instruction_info, false, &gva))
> +		return 1;
> +	if (kvm_read_guest_virt(&vcpu->arch.emulate_ctxt, gva, &vpid,
> +				sizeof(u32), &e)) {
> +		kvm_inject_page_fault(vcpu, &e);
> +		return 1;
> +	}
> +
> +	switch (type) {
> +	case VMX_VPID_EXTENT_ALL_CONTEXT:
> +		if (get_vmcs12(vcpu)->virtual_processor_id == 0) {
> +			nested_vmx_failValid(vcpu,
> +				VMXERR_INVALID_OPERAND_TO_INVEPT_INVVPID);
> +			return 1;
> +		}
> +		vmx_flush_tlb(vcpu);
> +		nested_vmx_succeed(vcpu);
> +		break;
> +	default:
> +		/* Trap single context invalidation invvpid calls */
> +		BUG_ON(1);

... which means that this BUG_ON(1) is guest triggerable.

Unit tests would have caught this... :)

Paolo

> +		break;
> +	}
> +
> +	skip_emulated_instruction(vcpu);
>  	return 1;
>  }
>  
> 
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