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[PATCH v3 3/5] x86/tdx: Add tdx_mcall_extend_rtmr() interface

Cedric Xing posted 5 patches 10 months, 1 week ago
There is a newer version of this series
[PATCH v3 3/5] x86/tdx: Add tdx_mcall_extend_rtmr() interface
Posted by Cedric Xing 10 months, 1 week ago 
The TDX guest exposes one MRTD (Build-time Measurement Register) and four
RTMR (Run-time Measurement Register) registers to record the build and boot
measurements of a virtual machine (VM). These registers are similar to PCR
(Platform Configuration Register) registers in the TPM (Trusted Platform
Module) space. This measurement data is used to implement security features
like attestation and trusted boot.

To facilitate updating the RTMR registers, the TDX module provides support
for the `TDG.MR.RTMR.EXTEND` TDCALL which can be used to securely extend
the RTMR registers.

Add helper function to update RTMR registers. It will be used by the TDX
guest driver in enabling RTMR extension support.

Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Signed-off-by: Cedric Xing <cedric.xing@intel.com>
---
 arch/x86/coco/tdx/tdx.c           | 36 ++++++++++++++++++++++++++++++++++++
 arch/x86/include/asm/shared/tdx.h |  1 +
 arch/x86/include/asm/tdx.h        |  2 ++
 3 files changed, 39 insertions(+)

diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
index edab6d6049be..b042ca74bcd3 100644
--- a/arch/x86/coco/tdx/tdx.c
+++ b/arch/x86/coco/tdx/tdx.c
@@ -36,6 +36,7 @@
 /* TDX Module call error codes */
 #define TDCALL_RETURN_CODE(a)	((a) >> 32)
 #define TDCALL_INVALID_OPERAND	0xc0000100
+#define TDCALL_OPERAND_BUSY	0x80000200
 
 #define TDREPORT_SUBTYPE_0	0
 
@@ -136,6 +137,41 @@ int tdx_mcall_get_report0(u8 *reportdata, u8 *tdreport)
 }
 EXPORT_SYMBOL_GPL(tdx_mcall_get_report0);
 
+/**
+ * tdx_mcall_extend_rtmr() - Wrapper to extend RTMR registers using
+ *			     TDG.MR.RTMR.EXTEND TDCALL.
+ * @index: Index of RTMR register to be extended.
+ * @data: Address of the input buffer with RTMR register extend data.
+ *
+ * Refer to section titled "TDG.MR.RTMR.EXTEND leaf" in the TDX Module
+ * v1.0 specification for more information on TDG.MR.RTMR.EXTEND TDCALL.
+ * It is used in the TDX guest driver module to allow user extend the
+ * RTMR registers (index > 1).
+ *
+ * Return 0 on success, -EINVAL for invalid operands, -EBUSY for busy
+ * operation or -EIO on other TDCALL failures.
+ */
+int tdx_mcall_extend_rtmr(u8 index, u8 *data)
+{
+	struct tdx_module_args args = {
+		.rcx = virt_to_phys(data),
+		.rdx = index,
+	};
+	u64 ret;
+
+	ret = __tdcall(TDG_MR_RTMR_EXTEND, &args);
+	if (ret) {
+		if (TDCALL_RETURN_CODE(ret) == TDCALL_INVALID_OPERAND)
+			return -EINVAL;
+		if (TDCALL_RETURN_CODE(ret) == TDCALL_OPERAND_BUSY)
+			return -EBUSY;
+		return -EIO;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(tdx_mcall_extend_rtmr);
+
 /**
  * tdx_hcall_get_quote() - Wrapper to request TD Quote using GetQuote
  *                         hypercall.
diff --git a/arch/x86/include/asm/shared/tdx.h b/arch/x86/include/asm/shared/tdx.h
index a28ff6b14145..738f583f65cb 100644
--- a/arch/x86/include/asm/shared/tdx.h
+++ b/arch/x86/include/asm/shared/tdx.h
@@ -13,6 +13,7 @@
 /* TDX module Call Leaf IDs */
 #define TDG_VP_VMCALL			0
 #define TDG_VP_INFO			1
+#define TDG_MR_RTMR_EXTEND		2
 #define TDG_VP_VEINFO_GET		3
 #define TDG_MR_REPORT			4
 #define TDG_MEM_PAGE_ACCEPT		6
diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
index 4a1922ec80cf..12d17f3ca301 100644
--- a/arch/x86/include/asm/tdx.h
+++ b/arch/x86/include/asm/tdx.h
@@ -64,6 +64,8 @@ bool tdx_early_handle_ve(struct pt_regs *regs);
 
 int tdx_mcall_get_report0(u8 *reportdata, u8 *tdreport);
 
+int tdx_mcall_extend_rtmr(u8 index, u8 *data);
+
 u64 tdx_hcall_get_quote(u8 *buf, size_t size);
 
 void __init tdx_dump_attributes(u64 td_attr);

-- 
2.43.0
Re: [PATCH v3 3/5] x86/tdx: Add tdx_mcall_extend_rtmr() interface
Posted by Dan Williams 10 months ago 
Cedric Xing wrote:
> The TDX guest exposes one MRTD (Build-time Measurement Register) and four
> RTMR (Run-time Measurement Register) registers to record the build and boot
> measurements of a virtual machine (VM). These registers are similar to PCR
> (Platform Configuration Register) registers in the TPM (Trusted Platform
> Module) space. This measurement data is used to implement security features
> like attestation and trusted boot.
> 
> To facilitate updating the RTMR registers, the TDX module provides support
> for the `TDG.MR.RTMR.EXTEND` TDCALL which can be used to securely extend
> the RTMR registers.
> 
> Add helper function to update RTMR registers. It will be used by the TDX
> guest driver in enabling RTMR extension support.
> 
> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>

Typically Signed-off-by without Co-developed-by means that the patch was
submitted upstream be Sathya, so did you also intend to add a
Co-developed-by or should this solo tag just be Reviewed-by?

> Signed-off-by: Cedric Xing <cedric.xing@intel.com>
> ---
>  arch/x86/coco/tdx/tdx.c           | 36 ++++++++++++++++++++++++++++++++++++
>  arch/x86/include/asm/shared/tdx.h |  1 +
>  arch/x86/include/asm/tdx.h        |  2 ++
>  3 files changed, 39 insertions(+)
> 
> diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
> index edab6d6049be..b042ca74bcd3 100644
> --- a/arch/x86/coco/tdx/tdx.c
> +++ b/arch/x86/coco/tdx/tdx.c
> @@ -36,6 +36,7 @@
>  /* TDX Module call error codes */
>  #define TDCALL_RETURN_CODE(a)	((a) >> 32)
>  #define TDCALL_INVALID_OPERAND	0xc0000100
> +#define TDCALL_OPERAND_BUSY	0x80000200
>  
>  #define TDREPORT_SUBTYPE_0	0
>  
> @@ -136,6 +137,41 @@ int tdx_mcall_get_report0(u8 *reportdata, u8 *tdreport)
>  }
>  EXPORT_SYMBOL_GPL(tdx_mcall_get_report0);
>  
> +/**
> + * tdx_mcall_extend_rtmr() - Wrapper to extend RTMR registers using
> + *			     TDG.MR.RTMR.EXTEND TDCALL.
> + * @index: Index of RTMR register to be extended.
> + * @data: Address of the input buffer with RTMR register extend data.
> + *
> + * Refer to section titled "TDG.MR.RTMR.EXTEND leaf" in the TDX Module
> + * v1.0 specification for more information on TDG.MR.RTMR.EXTEND TDCALL.
> + * It is used in the TDX guest driver module to allow user extend the
> + * RTMR registers (index > 1).
> + *
> + * Return 0 on success, -EINVAL for invalid operands, -EBUSY for busy
> + * operation or -EIO on other TDCALL failures.
> + */
> +int tdx_mcall_extend_rtmr(u8 index, u8 *data)
> +{
> +	struct tdx_module_args args = {
> +		.rcx = virt_to_phys(data),
> +		.rdx = index,
> +	};
> +	u64 ret;
> +
> +	ret = __tdcall(TDG_MR_RTMR_EXTEND, &args);
> +	if (ret) {
> +		if (TDCALL_RETURN_CODE(ret) == TDCALL_INVALID_OPERAND)
> +			return -EINVAL;

Here is where the ABI documentation can help to make sure that userspace
can tell the difference between userspace bugs, kernel bugs, or TDX
internal errors. So perhaps translate this EINVAL to 
ENXIO in tsm-mr.c. Otherwise, this patch looks good to me:

Reviewed-by: Dan Williams <dan.j.williams@intel.com>

[..]
Re: [PATCH v3 3/5] x86/tdx: Add tdx_mcall_extend_rtmr() interface
Posted by Xing, Cedric 10 months ago 
On 4/9/2025 12:10 AM, Dan Williams wrote:
> Cedric Xing wrote:
>> The TDX guest exposes one MRTD (Build-time Measurement Register) and four
>> RTMR (Run-time Measurement Register) registers to record the build and boot
>> measurements of a virtual machine (VM). These registers are similar to PCR
>> (Platform Configuration Register) registers in the TPM (Trusted Platform
>> Module) space. This measurement data is used to implement security features
>> like attestation and trusted boot.
>>
>> To facilitate updating the RTMR registers, the TDX module provides support
>> for the `TDG.MR.RTMR.EXTEND` TDCALL which can be used to securely extend
>> the RTMR registers.
>>
>> Add helper function to update RTMR registers. It will be used by the TDX
>> guest driver in enabling RTMR extension support.
>>
>> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
> 
> Typically Signed-off-by without Co-developed-by means that the patch was
> submitted upstream be Sathya, so did you also intend to add a
> Co-developed-by or should this solo tag just be Reviewed-by?
> 
I did modify slightly this commit from Sathya. I could be wrong but was 
told that "Signed-off-by:" was necessary to certify I had the authority 
to submit this patch. scripts/checkpatch.py complained about the 
co-existence of "Co-developed-by" and "Signed-off-by". So I had to keep 
the "Signed-off-by" tag only.

>> Signed-off-by: Cedric Xing <cedric.xing@intel.com>
>> ---
>>   arch/x86/coco/tdx/tdx.c           | 36 ++++++++++++++++++++++++++++++++++++
>>   arch/x86/include/asm/shared/tdx.h |  1 +
>>   arch/x86/include/asm/tdx.h        |  2 ++
>>   3 files changed, 39 insertions(+)
>>
>> diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
>> index edab6d6049be..b042ca74bcd3 100644
>> --- a/arch/x86/coco/tdx/tdx.c
>> +++ b/arch/x86/coco/tdx/tdx.c
>> @@ -36,6 +36,7 @@
>>   /* TDX Module call error codes */
>>   #define TDCALL_RETURN_CODE(a)	((a) >> 32)
>>   #define TDCALL_INVALID_OPERAND	0xc0000100
>> +#define TDCALL_OPERAND_BUSY	0x80000200
>>   
>>   #define TDREPORT_SUBTYPE_0	0
>>   
>> @@ -136,6 +137,41 @@ int tdx_mcall_get_report0(u8 *reportdata, u8 *tdreport)
>>   }
>>   EXPORT_SYMBOL_GPL(tdx_mcall_get_report0);
>>   
>> +/**
>> + * tdx_mcall_extend_rtmr() - Wrapper to extend RTMR registers using
>> + *			     TDG.MR.RTMR.EXTEND TDCALL.
>> + * @index: Index of RTMR register to be extended.
>> + * @data: Address of the input buffer with RTMR register extend data.
>> + *
>> + * Refer to section titled "TDG.MR.RTMR.EXTEND leaf" in the TDX Module
>> + * v1.0 specification for more information on TDG.MR.RTMR.EXTEND TDCALL.
>> + * It is used in the TDX guest driver module to allow user extend the
>> + * RTMR registers (index > 1).
>> + *
>> + * Return 0 on success, -EINVAL for invalid operands, -EBUSY for busy
>> + * operation or -EIO on other TDCALL failures.
>> + */
>> +int tdx_mcall_extend_rtmr(u8 index, u8 *data)
>> +{
>> +	struct tdx_module_args args = {
>> +		.rcx = virt_to_phys(data),
>> +		.rdx = index,
>> +	};
>> +	u64 ret;
>> +
>> +	ret = __tdcall(TDG_MR_RTMR_EXTEND, &args);
>> +	if (ret) {
>> +		if (TDCALL_RETURN_CODE(ret) == TDCALL_INVALID_OPERAND)
>> +			return -EINVAL;
> 
> Here is where the ABI documentation can help to make sure that userspace
> can tell the difference between userspace bugs, kernel bugs, or TDX
> internal errors. So perhaps translate this EINVAL to
> ENXIO in tsm-mr.c. Otherwise, this patch looks good to me:
> 
> Reviewed-by: Dan Williams <dan.j.williams@intel.com>
> 
Agreed. I'll change -EINVAL to -ENXIO as this would be due to the 
inability to convert VA to GPA.

> [..]

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