Date:   Tue, 14 Feb 2023 13:42:53 +0100
From:   Peter Zijlstra <peterz@infradead.org>
To:     Kai Huang <kai.huang@intel.com>
Cc:     linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
        linux-mm@kvack.org, dave.hansen@intel.com, tglx@linutronix.de,
        seanjc@google.com, pbonzini@redhat.com, dan.j.williams@intel.com,
        rafael.j.wysocki@intel.com, kirill.shutemov@linux.intel.com,
        ying.huang@intel.com, reinette.chatre@intel.com,
        len.brown@intel.com, tony.luck@intel.com, ak@linux.intel.com,
        isaku.yamahata@intel.com, chao.gao@intel.com,
        sathyanarayanan.kuppuswamy@linux.intel.com, david@redhat.com,
        bagasdotme@gmail.com, sagis@google.com, imammedo@redhat.com
Subject: Re: [PATCH v9 05/18] x86/virt/tdx: Add SEAMCALL infrastructure
Message-ID: <Y+uBzZOUt95YTQ4J@hirez.programming.kicks-ass.net>
References: <cover.1676286526.git.kai.huang@intel.com>
 <dd18d6b42768e0107d212fdebedae92cfd72cfe1.1676286526.git.kai.huang@intel.com>
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On Tue, Feb 14, 2023 at 12:59:12AM +1300, 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)
> +{
> +	int cpu, ret = 0;
> +	u64 sret;
> +
> +	/* Need a stable CPU id for printing error message */
> +	cpu = get_cpu();
> +
> +	sret = __seamcall(fn, rcx, rdx, r8, r9, out);
> +
> +	/* Save SEAMCALL return code if the caller wants it */
> +	if (seamcall_ret)
> +		*seamcall_ret = sret;
> +
> +	/* SEAMCALL was successful */
> +	if (!sret)
> +		goto out;

I'm thinking you want if (likely(!sret)), here. That whole switch thing
should end up in cold storage.

> +
> +	switch (sret) {
> +	case TDX_SEAMCALL_GP:
> +		/*
> +		 * tdx_enable() has already checked that BIOS has
> +		 * enabled TDX at the very beginning before going
> +		 * forward.  It's likely a firmware bug if the
> +		 * SEAMCALL still caused #GP.
> +		 */
> +		pr_err_once("[firmware bug]: TDX is not enabled by BIOS.\n");
> +		ret = -ENODEV;
> +		break;
> +	case TDX_SEAMCALL_VMFAILINVALID:
> +		pr_err_once("TDX module is not loaded.\n");
> +		ret = -ENODEV;
> +		break;
> +	case TDX_SEAMCALL_UD:
> +		pr_err_once("SEAMCALL failed: CPU %d is not in VMX operation.\n",
> +				cpu);
> +		ret = -EINVAL;
> +		break;
> +	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);
> +		ret = -EIO;
> +	}
> +out:
> +	put_cpu();
> +	return ret;
> +}