Re: [RFC PATCH v2 61/69] KVM: VMX: Move AR_BYTES encoder/decoder helpers to common.h

[Paolo Bonzini]

On 03/07/21 00:05, isaku.yamahata@xxxxxxxxx wrote:
> From: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
>
> Move the AR_BYTES helpers to common.h so that future patches can reuse
> them to decode/encode AR for TDX.
>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
> ---
>   arch/x86/kvm/vmx/common.h | 41 ++++++++++++++++++++++++++++++++++
>   arch/x86/kvm/vmx/vmx.c    | 47 ++++-----------------------------------
>   2 files changed, 45 insertions(+), 43 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx/common.h b/arch/x86/kvm/vmx/common.h
> index aa6a569b87d1..755aaec85199 100644
> --- a/arch/x86/kvm/vmx/common.h
> +++ b/arch/x86/kvm/vmx/common.h
> @@ -4,6 +4,7 @@
>   
>   #include <linux/kvm_host.h>
>   
> +#include <asm/kvm.h>
>   #include <asm/traps.h>
>   #include <asm/vmx.h>
>   
> @@ -119,4 +120,44 @@ static inline int __vmx_handle_ept_violation(struct kvm_vcpu *vcpu, gpa_t gpa,
>   	return kvm_mmu_page_fault(vcpu, gpa, error_code, NULL, 0);
>   }
>   
> +static inline u32 vmx_encode_ar_bytes(struct kvm_segment *var)
> +{
> +	u32 ar;
> +
> +	if (var->unusable || !var->present)
> +		ar = 1 << 16;
> +	else {
> +		ar = var->type & 15;
> +		ar |= (var->s & 1) << 4;
> +		ar |= (var->dpl & 3) << 5;
> +		ar |= (var->present & 1) << 7;
> +		ar |= (var->avl & 1) << 12;
> +		ar |= (var->l & 1) << 13;
> +		ar |= (var->db & 1) << 14;
> +		ar |= (var->g & 1) << 15;
> +	}
> +
> +	return ar;
> +}
> +
> +static inline void vmx_decode_ar_bytes(u32 ar, struct kvm_segment *var)
> +{
> +	var->unusable = (ar >> 16) & 1;
> +	var->type = ar & 15;
> +	var->s = (ar >> 4) & 1;
> +	var->dpl = (ar >> 5) & 3;
> +	/*
> +	 * Some userspaces do not preserve unusable property. Since usable
> +	 * segment has to be present according to VMX spec we can use present
> +	 * property to amend userspace bug by making unusable segment always
> +	 * nonpresent. vmx_encode_ar_bytes() already marks nonpresent
> +	 * segment as unusable.
> +	 */
> +	var->present = !var->unusable;
> +	var->avl = (ar >> 12) & 1;
> +	var->l = (ar >> 13) & 1;
> +	var->db = (ar >> 14) & 1;
> +	var->g = (ar >> 15) & 1;
> +}
> +
>   #endif /* __KVM_X86_VMX_COMMON_H */
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 3c3bfc80d2bb..40843ca2fb33 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -365,8 +365,6 @@ static const struct kernel_param_ops vmentry_l1d_flush_ops = {
>   };
>   module_param_cb(vmentry_l1d_flush, &vmentry_l1d_flush_ops, NULL, 0644);
>   
> -static u32 vmx_segment_access_rights(struct kvm_segment *var);
> -
>   void vmx_vmexit(void);
>   
>   #define vmx_insn_failed(fmt...)		\
> @@ -2826,7 +2824,7 @@ static void fix_rmode_seg(int seg, struct kvm_segment *save)
>   	vmcs_write16(sf->selector, var.selector);
>   	vmcs_writel(sf->base, var.base);
>   	vmcs_write32(sf->limit, var.limit);
> -	vmcs_write32(sf->ar_bytes, vmx_segment_access_rights(&var));
> +	vmcs_write32(sf->ar_bytes, vmx_encode_ar_bytes(&var));
>   }
>   
>   static void enter_rmode(struct kvm_vcpu *vcpu)
> @@ -3217,7 +3215,6 @@ void vmx_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
>   void vmx_get_segment(struct kvm_vcpu *vcpu, struct kvm_segment *var, int seg)
>   {
>   	struct vcpu_vmx *vmx = to_vmx(vcpu);
> -	u32 ar;
>   
>   	if (vmx->rmode.vm86_active && seg != VCPU_SREG_LDTR) {
>   		*var = vmx->rmode.segs[seg];
> @@ -3231,23 +3228,7 @@ void vmx_get_segment(struct kvm_vcpu *vcpu, struct kvm_segment *var, int seg)
>   	var->base = vmx_read_guest_seg_base(vmx, seg);
>   	var->limit = vmx_read_guest_seg_limit(vmx, seg);
>   	var->selector = vmx_read_guest_seg_selector(vmx, seg);
> -	ar = vmx_read_guest_seg_ar(vmx, seg);
> -	var->unusable = (ar >> 16) & 1;
> -	var->type = ar & 15;
> -	var->s = (ar >> 4) & 1;
> -	var->dpl = (ar >> 5) & 3;
> -	/*
> -	 * Some userspaces do not preserve unusable property. Since usable
> -	 * segment has to be present according to VMX spec we can use present
> -	 * property to amend userspace bug by making unusable segment always
> -	 * nonpresent. vmx_segment_access_rights() already marks nonpresent
> -	 * segment as unusable.
> -	 */
> -	var->present = !var->unusable;
> -	var->avl = (ar >> 12) & 1;
> -	var->l = (ar >> 13) & 1;
> -	var->db = (ar >> 14) & 1;
> -	var->g = (ar >> 15) & 1;
> +	vmx_decode_ar_bytes(vmx_read_guest_seg_ar(vmx, seg), var);
>   }
>   
>   static u64 vmx_get_segment_base(struct kvm_vcpu *vcpu, int seg)
> @@ -3273,26 +3254,6 @@ int vmx_get_cpl(struct kvm_vcpu *vcpu)
>   	}
>   }
>   
> -static u32 vmx_segment_access_rights(struct kvm_segment *var)
> -{
> -	u32 ar;
> -
> -	if (var->unusable || !var->present)
> -		ar = 1 << 16;
> -	else {
> -		ar = var->type & 15;
> -		ar |= (var->s & 1) << 4;
> -		ar |= (var->dpl & 3) << 5;
> -		ar |= (var->present & 1) << 7;
> -		ar |= (var->avl & 1) << 12;
> -		ar |= (var->l & 1) << 13;
> -		ar |= (var->db & 1) << 14;
> -		ar |= (var->g & 1) << 15;
> -	}
> -
> -	return ar;
> -}
> -
>   void vmx_set_segment(struct kvm_vcpu *vcpu, struct kvm_segment *var, int seg)
>   {
>   	struct vcpu_vmx *vmx = to_vmx(vcpu);
> @@ -3327,7 +3288,7 @@ void vmx_set_segment(struct kvm_vcpu *vcpu, struct kvm_segment *var, int seg)
>   	if (is_unrestricted_guest(vcpu) && (seg != VCPU_SREG_LDTR))
>   		var->type |= 0x1; /* Accessed */
>   
> -	vmcs_write32(sf->ar_bytes, vmx_segment_access_rights(var));
> +	vmcs_write32(sf->ar_bytes, vmx_encode_ar_bytes(var));
>   
>   out:
>   	vmx->emulation_required = emulation_required(vcpu);
> @@ -3374,7 +3335,7 @@ static bool rmode_segment_valid(struct kvm_vcpu *vcpu, int seg)
>   	var.dpl = 0x3;
>   	if (seg == VCPU_SREG_CS)
>   		var.type = 0x3;
> -	ar = vmx_segment_access_rights(&var);
> +	ar = vmx_encode_ar_bytes(&var);
>   
>   	if (var.base != (var.selector << 4))
>   		return false;

Reviewed-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>