linux-kernel - RE: [RFC PATCH V2 06/18] x86/hyperv: Use vmmcall to implement hvcall in sev-snp enlightened guest

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Date:   Mon, 9 Jan 2023 07:24:37 +0000
From:   Dexuan Cui <decui@...rosoft.com>
To:     Tianyu Lan <ltykernel@...il.com>,
        "luto@...nel.org" <luto@...nel.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
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        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "jgross@...e.com" <jgross@...e.com>,
        Tianyu Lan <Tianyu.Lan@...rosoft.com>,
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CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>
Subject: RE: [RFC PATCH V2 06/18] x86/hyperv: Use vmmcall to implement hvcall
 in sev-snp enlightened guest

> From: Tianyu Lan <ltykernel@...il.com>
> Sent: Friday, November 18, 2022 7:46 PM
> --- a/arch/x86/include/asm/mshyperv.h
> +++ b/arch/x86/include/asm/mshyperv.h
> @@ -45,16 +45,25 @@ static inline u64 hv_do_hypercall(u64 control, void
> *input, void *output)
>  	u64 hv_status;
> 
>  #ifdef CONFIG_X86_64
> -	if (!hv_hypercall_pg)
> -		return U64_MAX;
> +	if (hv_isolation_type_en_snp()) {
> +		__asm__ __volatile__("mov %4, %%r8\n"
> +				"vmmcall"
> +				: "=a" (hv_status), ASM_CALL_CONSTRAINT,
> +				"+c" (control), "+d" (input_address)
> +				:  "r" (output_address)
> +				: "cc", "memory", "r8", "r9", "r10", "r11");

Add a "return hv_status;" here to avoid chaning the indentation below?

> +	} else {
> +		if (!hv_hypercall_pg)
> +			return U64_MAX;
> 
> -	__asm__ __volatile__("mov %4, %%r8\n"
> -			     CALL_NOSPEC
> -			     : "=a" (hv_status), ASM_CALL_CONSTRAINT,
> -			       "+c" (control), "+d" (input_address)
> -			     :  "r" (output_address),
> -				THUNK_TARGET(hv_hypercall_pg)
> -			     : "cc", "memory", "r8", "r9", "r10", "r11");
> +		__asm__ __volatile__("mov %4, %%r8\n"
> +				CALL_NOSPEC
> +				: "=a" (hv_status), ASM_CALL_CONSTRAINT,
> +				"+c" (control), "+d" (input_address)
> +				:  "r" (output_address),
> +					THUNK_TARGET(hv_hypercall_pg)
> +				: "cc", "memory", "r8", "r9", "r10", "r11");
> +	}
>  #else