Re: [PATCH v17 1/3] x86/tdx: Add a wrapper to get TDREPORT from the TDX Module

From: Sathyanarayanan Kuppuswamy  <sathyanarayanan.kuppuswamy@linux.intel.com>
To: Dave Hansen <dave.hansen@intel.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	x86@kernel.org, Shuah Khan <shuah@kernel.org>,
	Jonathan Corbet <corbet@lwn.net>
Cc: "H . Peter Anvin" <hpa@zytor.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
	Tony Luck <tony.luck@intel.com>, Kai Huang <kai.huang@intel.com>,
	Wander Lairson Costa <wander@redhat.com>,
	Isaku Yamahata <isaku.yamahata@gmail.com>,
	marcelo.cerri@canonical.com, tim.gardner@canonical.com,
	khalid.elmously@canonical.com, philip.cox@canonical.com,
	linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org,
	linux-doc@vger.kernel.org
Subject: Re: [PATCH v17 1/3] x86/tdx: Add a wrapper to get TDREPORT from the TDX Module
Date: Tue, 15 Nov 2022 22:25:50 -0800	[thread overview]
Message-ID: <556a2475-f0e1-d1cf-1c46-bbe052e5ef40@linux.intel.com> (raw)
In-Reply-To: <e7147e03-705e-d2a8-9c9c-b4243ed5b451@intel.com>

Hi Dave,

On 11/14/22 4:54 PM, Dave Hansen wrote:
>> In both the commit log and the comments, I can highlight the "subtype 0"
>> information. Will that work for you, or do you prefer that this wrapper
>> take the "subtype" option as argument and we pass 0 for the subtype value
>> from the TDX guest driver?
> I actually think it's a *lot* more clear if the User<->Kernel ABI just
> takes the subtype.  But, I also heard Greg's concerns about making the
> ABI _too_ open-ended.
> 
> So, I really don't care.  Just make it clear that, as is, this ABI is
> not the "TDREPORT ABI".
> 

Are you fine with the following version?

+/* TDX Module call error codes */
+#define TDCALL_RETURN_CODE(a)  ((a) >> 32)
+#define TDCALL_INVALID_OPERAND 0xc0000100
+
+#define TDREPORT_SUBTYPE_0     0
+ 
+/**
+ * tdx_mcall_get_report0() - Wrapper to get TDREPORT0 (a.k.a. TDREPORT
+ *                           subtype 0) using TDG.MR.REPORT TDCALL.
+ * @reportdata: Address of the input buffer which contains user-defined
+ *              REPORTDATA to be included into TDREPORT.
+ * @tdreport: Address of the output buffer to store TDREPORT.
+ *
+ * Refer to section titled "TDG.MR.REPORT leaf" in the TDX Module
+ * v1.0 specification for more information on TDG.MR.REPORT TDCALL.
+ * It is used in the TDX guest driver module to get the TDREPORT0.
+ *
+ * Return 0 on success, -EINVAL for invalid operands, or -EIO on
+ * other TDCALL failures.
+ */
+int tdx_mcall_get_report0(u8 *reportdata, u8 *tdreport)
+{
+       u64 ret;
+
+       ret = __tdx_module_call(TDX_GET_REPORT, virt_to_phys(tdreport),
+                               virt_to_phys(reportdata), TDREPORT_SUBTYPE_0,
+                               0, NULL);
+       if (ret) {
+               if (TDCALL_RETURN_CODE(ret) == TDCALL_INVALID_OPERAND)
+                       return -EINVAL;
+               return -EIO;
+       }
+
+       return 0;
+}
+EXPORT_SYMBOL_GPL(tdx_mcall_get_report0);

-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer