linux-kernel - Re: [PATCH v12 05/22] x86/virt/tdx: Add SEAMCALL infrastructure

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Date:   Tue, 27 Jun 2023 12:48:56 +0300
From:   kirill.shutemov@...ux.intel.com
To:     Kai Huang <kai.huang@...el.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        linux-mm@...ck.org, x86@...nel.org, dave.hansen@...el.com,
        tony.luck@...el.com, peterz@...radead.org, tglx@...utronix.de,
        bp@...en8.de, mingo@...hat.com, hpa@...or.com, seanjc@...gle.com,
        pbonzini@...hat.com, david@...hat.com, dan.j.williams@...el.com,
        rafael.j.wysocki@...el.com, ashok.raj@...el.com,
        reinette.chatre@...el.com, len.brown@...el.com, ak@...ux.intel.com,
        isaku.yamahata@...el.com, ying.huang@...el.com, chao.gao@...el.com,
        sathyanarayanan.kuppuswamy@...ux.intel.com, nik.borisov@...e.com,
        bagasdotme@...il.com, sagis@...gle.com, imammedo@...hat.com
Subject: Re: [PATCH v12 05/22] x86/virt/tdx: Add SEAMCALL infrastructure

On Tue, Jun 27, 2023 at 02:12:35AM +1200, Kai Huang wrote:
> +/*
> + * Wrapper of __seamcall() to convert SEAMCALL leaf function error code
> + * to kernel error code.  @seamcall_ret and @out contain the SEAMCALL
> + * leaf function return code and the additional output respectively if
> + * not NULL.
> + */
> +static int __always_unused seamcall(u64 fn, u64 rcx, u64 rdx, u64 r8, u64 r9,
> +				    u64 *seamcall_ret,
> +				    struct tdx_module_output *out)
> +{
> +	u64 sret;
> +	int cpu;
> +
> +	/* Need a stable CPU id for printing error message */
> +	cpu = get_cpu();
> +	sret = __seamcall(fn, rcx, rdx, r8, r9, out);
> +	put_cpu();
> +
> +	/* Save SEAMCALL return code if the caller wants it */
> +	if (seamcall_ret)
> +		*seamcall_ret = sret;
> +
> +	switch (sret) {
> +	case 0:
> +		/* SEAMCALL was successful */
> +		return 0;
> +	case TDX_SEAMCALL_VMFAILINVALID:
> +		pr_err_once("module is not loaded.\n");
> +		return -ENODEV;
> +	default:
> +		pr_err_once("SEAMCALL failed: CPU %d: leaf %llu, error 0x%llx.\n",
> +				cpu, fn, sret);
> +		if (out)
> +			pr_err_once("additional output: rcx 0x%llx, rdx 0x%llx, r8 0x%llx, r9 0x%llx, r10 0x%llx, r11 0x%llx.\n",
> +					out->rcx, out->rdx, out->r8,
> +					out->r9, out->r10, out->r11);

This look excessively noisy.

Don't we have SEAMCALL leafs that can fail in normal situation? Like
TDX_OPERAND_BUSY error code that indicate that operation likely will
succeed on retry.

Or is that wrapper only used for never-fail SEAMCALLs? If so, please
document it.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov