RE: [PATCH 9/24] Implement VMCLEAR

["Dong, Eddie" <eddie.dong@intel.com>]

Nadav Har'El wrote:
> This patch implements the VMCLEAR instruction.
> 
> Signed-off-by: Nadav Har'El <nyh@il.ibm.com>
> ---
> --- .before/arch/x86/kvm/vmx.c	2010-06-13 15:01:29.000000000 +0300
> +++ .after/arch/x86/kvm/vmx.c	2010-06-13 15:01:29.000000000 +0300
> @@ -138,6 +138,8 @@ struct __attribute__ ((__packed__)) vmcs
>  	 */
>  	u32 revision_id;
>  	u32 abort;
> +
> +	bool launch_state; /* set to 0 by VMCLEAR, to 1 by VMLAUNCH */
>  };
> 
>  struct vmcs_list {
> @@ -3827,6 +3829,46 @@ static int read_guest_vmcs_gpa(struct kv
>  	return 0;
>  }
> 
> +static void clear_rflags_cf_zf(struct kvm_vcpu *vcpu)
> +{
> +	unsigned long rflags;
> +	rflags = vmx_get_rflags(vcpu);
> +	rflags &= ~(X86_EFLAGS_CF | X86_EFLAGS_ZF);
> +	vmx_set_rflags(vcpu, rflags);
> +}
> +
> +/* Emulate the VMCLEAR instruction */
> +static int handle_vmclear(struct kvm_vcpu *vcpu)
> +{
> +	struct vcpu_vmx *vmx = to_vmx(vcpu);
> +	gpa_t guest_vmcs_addr, save_current_vmptr;
> +
> +	if (!nested_vmx_check_permission(vcpu))
> +		return 1;
> +
> +	if (read_guest_vmcs_gpa(vcpu, &guest_vmcs_addr))
> +		return 1;
> +

SDM implements alignment check, range check and reserve bit check and may generate VMfail(VMCLEAR with invalid physical address).
As well as "addr != VMXON pointer" check
Missed?

> +	save_current_vmptr = vmx->nested.current_vmptr;
> +
> +	vmx->nested.current_vmptr = guest_vmcs_addr;
> +	if (!nested_map_current(vcpu))
> +		return 1;
> +	vmx->nested.current_l2_page->launch_state = 0;
> +	nested_unmap_current(vcpu);
> +
> +	nested_free_current_vmcs(vcpu);
> +
> +	if (save_current_vmptr == guest_vmcs_addr)
> +		vmx->nested.current_vmptr = -1ull;
> +	else
> +		vmx->nested.current_vmptr = save_current_vmptr;
> +
> +	skip_emulated_instruction(vcpu);
> +	clear_rflags_cf_zf(vcpu);

SDM has formal definition of VMSucceed. Cleating CF/ZF only is not sufficient as SDM 2B 5.2 mentioned.
Any special concern here?

BTW, should we define formal VMfail() & VMsucceed() API for easy understand and map to SDM?

> +	return 1;
> +}
> +
>  static int handle_invlpg(struct kvm_vcpu *vcpu)
>  {
>  	unsigned long exit_qualification = vmcs_readl(EXIT_QUALIFICATION);
> @@ -4109,7 +4151,7 @@ static int (*kvm_vmx_exit_handlers[])(st
>  	[EXIT_REASON_HLT]                     = handle_halt,
>  	[EXIT_REASON_INVLPG]		      = handle_invlpg,
>  	[EXIT_REASON_VMCALL]                  = handle_vmcall,
> -	[EXIT_REASON_VMCLEAR]	              = handle_vmx_insn,
> +	[EXIT_REASON_VMCLEAR]	              = handle_vmclear,
>  	[EXIT_REASON_VMLAUNCH]                = handle_vmx_insn,
>  	[EXIT_REASON_VMPTRLD]                 = handle_vmx_insn,
>  	[EXIT_REASON_VMPTRST]                 = handle_vmx_insn,