Re: [PATCH V7 5/9] x86/sev-es: Expose __sev_es_ghcb_hv_call() to call ghcb hv call out of sev code

[Tianyu Lan <ltykernel@gmail.com>]

Hi @Tom and Borislav:
      Please have a look at this patch. If it's ok, could you give your ack.

Thanks.

On 10/6/2021 2:36 PM, Tianyu Lan wrote:
> From: Tianyu Lan <Tianyu.Lan@microsoft.com>
> 
> Hyper-V also needs to call ghcb hv call to write/read MSR in Isolation VM.
> So expose __sev_es_ghcb_hv_call() to call it in the Hyper-V code.
> 
> Signed-off-by: Tianyu Lan <Tianyu.Lan@microsoft.com>
> ---
>   arch/x86/include/asm/sev.h   | 10 +++++++++
>   arch/x86/kernel/sev-shared.c | 43 +++++++++++++++++++++++++-----------
>   2 files changed, 40 insertions(+), 13 deletions(-)
> 
> diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
> index fa5cd05d3b5b..2e96869f3e9b 100644
> --- a/arch/x86/include/asm/sev.h
> +++ b/arch/x86/include/asm/sev.h
> @@ -81,12 +81,22 @@ static __always_inline void sev_es_nmi_complete(void)
>   		__sev_es_nmi_complete();
>   }
>   extern int __init sev_es_efi_map_ghcbs(pgd_t *pgd);
> +extern enum es_result __sev_es_ghcb_hv_call(struct ghcb *ghcb,
> +					    u64 exit_code, u64 exit_info_1,
> +					    u64 exit_info_2);
>   #else
>   static inline void sev_es_ist_enter(struct pt_regs *regs) { }
>   static inline void sev_es_ist_exit(void) { }
>   static inline int sev_es_setup_ap_jump_table(struct real_mode_header *rmh) { return 0; }
>   static inline void sev_es_nmi_complete(void) { }
>   static inline int sev_es_efi_map_ghcbs(pgd_t *pgd) { return 0; }
> +static inline enum es_result
> +__sev_es_ghcb_hv_call(struct ghcb *ghcb,
> +		      u64 exit_code, u64 exit_info_1,
> +		      u64 exit_info_2)
> +{
> +	return ES_VMM_ERROR;
> +}
>   #endif
>   
>   #endif
> diff --git a/arch/x86/kernel/sev-shared.c b/arch/x86/kernel/sev-shared.c
> index 9f90f460a28c..946c203be08c 100644
> --- a/arch/x86/kernel/sev-shared.c
> +++ b/arch/x86/kernel/sev-shared.c
> @@ -94,10 +94,13 @@ static void vc_finish_insn(struct es_em_ctxt *ctxt)
>   	ctxt->regs->ip += ctxt->insn.length;
>   }
>   
> -static enum es_result sev_es_ghcb_hv_call(struct ghcb *ghcb,
> -					  struct es_em_ctxt *ctxt,
> -					  u64 exit_code, u64 exit_info_1,
> -					  u64 exit_info_2)
> +/*
> + * __sev_es_ghcb_hv_call() is also used in the other platform code(e.g
> + * Hyper-V).
> + */
> +enum es_result __sev_es_ghcb_hv_call(struct ghcb *ghcb,
> +				     u64 exit_code, u64 exit_info_1,
> +				     u64 exit_info_2)
>   {
>   	enum es_result ret;
>   
> @@ -109,15 +112,33 @@ static enum es_result sev_es_ghcb_hv_call(struct ghcb *ghcb,
>   	ghcb_set_sw_exit_info_1(ghcb, exit_info_1);
>   	ghcb_set_sw_exit_info_2(ghcb, exit_info_2);
>   
> -	sev_es_wr_ghcb_msr(__pa(ghcb));
>   	VMGEXIT();
>   
> +	if (ghcb->save.sw_exit_info_1 & 0xffffffff)
> +		ret = ES_VMM_ERROR;
> +	else
> +		ret = ES_OK;
> +
> +	return ret;
> +}
> +
> +static enum es_result sev_es_ghcb_hv_call(struct ghcb *ghcb,
> +					  struct es_em_ctxt *ctxt,
> +					  u64 exit_code, u64 exit_info_1,
> +					  u64 exit_info_2)
> +{
> +	enum es_result ret;
> +
> +	sev_es_wr_ghcb_msr(__pa(ghcb));
> +
> +	ret = __sev_es_ghcb_hv_call(ghcb, exit_code, exit_info_1,
> +					 exit_info_2);
> +	if (ret == ES_OK)
> +		return ret;
> +
>   	if ((ghcb->save.sw_exit_info_1 & 0xffffffff) == 1) {
>   		u64 info = ghcb->save.sw_exit_info_2;
> -		unsigned long v;
> -
> -		info = ghcb->save.sw_exit_info_2;
> -		v = info & SVM_EVTINJ_VEC_MASK;
> +		unsigned long v = info & SVM_EVTINJ_VEC_MASK;
>   
>   		/* Check if exception information from hypervisor is sane. */
>   		if ((info & SVM_EVTINJ_VALID) &&
> @@ -127,11 +148,7 @@ static enum es_result sev_es_ghcb_hv_call(struct ghcb *ghcb,
>   			if (info & SVM_EVTINJ_VALID_ERR)
>   				ctxt->fi.error_code = info >> 32;
>   			ret = ES_EXCEPTION;
> -		} else {
> -			ret = ES_VMM_ERROR;
>   		}
> -	} else {
> -		ret = ES_OK;
>   	}
>   
>   	return ret;
>