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

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Date:   Tue, 15 Nov 2022 22:25:50 -0800
From:   Sathyanarayanan Kuppuswamy 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
To:     Dave Hansen <dave.hansen@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        Shuah Khan <shuah@...nel.org>, Jonathan Corbet <corbet@....net>
Cc:     "H . Peter Anvin" <hpa@...or.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Tony Luck <tony.luck@...el.com>,
        Kai Huang <kai.huang@...el.com>,
        Wander Lairson Costa <wander@...hat.com>,
        Isaku Yamahata <isaku.yamahata@...il.com>,
        marcelo.cerri@...onical.com, tim.gardner@...onical.com,
        khalid.elmously@...onical.com, philip.cox@...onical.com,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
        linux-doc@...r.kernel.org
Subject: Re: [PATCH v17 1/3] x86/tdx: Add a wrapper to get TDREPORT from the
 TDX Module

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