Hi Dionna Amalie Glaze,

Thanks for the review.

On 4/26/23 8:40 AM, Dionna Amalie Glaze wrote:

On Wed, Apr 12, 2023 at 8:42 PM Kuppuswamy Sathyanarayanan sathyanarayanan.kuppuswamy@linux.intel.com wrote:

...

In TDX guest, the second stage in attestation process is to send the TDREPORT to QE/QGS to generate the TD Quote. For platforms that does

Is it common to state TDREPORT when TDREPORT_STRUCT is meant? Here and below. The GHCI documentation seems to use the two as synonyms but doesn't explicitly say so.

In general, we just use the term "TDREPORT" to refer to the generated report. TDREPORT_STRUCT is mainly used when we want to make reference to the structure of the TDREPORT in the GHCI specification (very rarely used). Also, as you mentioned, even in GHCI specification, both terms are used as synonyms.

nit: platforms that do not

...

not support communication channels like vsock or TCP/IP, implement support to get TD Quote using hypercall. GetQuote hypercall can be used by the TD guest to request VMM facilitate the Quote generation via

nit: request the VMM to facilitate

...

QE/QGS. More details about GetQuote hypercall can be found in TDX Guest-Host Communication Interface (GHCI) for Intel TDX 1.0, section titled "TDG.VP.VMCALL<GetQuote>".

Add support for TDX_CMD_GET_QUOTE IOCTL to allow attestation agent

nit: an attestation agent to

...

submit GetQuote requests from the user space using GetQuote hypercall.

Since GetQuote is an asynchronous request hypercall, VMM will use callback interrupt vector configured by SetupEventNotifyInterrupt

nit: a callback interrupt vector configured by the SetupEventNotifyInterrupt

...

hypercall to notify the guest about Quote generation completion or failure. So register an IRQ handler for it.

GetQuote TDVMCALL requires TD guest pass a 4K aligned shared buffer with TDREPORT data as input, which is further used by the VMM to copy the TD Quote result after successful Quote generation. To create the shared buffer, allocate the required memory using alloc_pages() and mark it shared using set_memory_decrypted() in tdx_guest_init(). This buffer will be re-used for GetQuote requests in TDX_CMD_GET_QUOTE

suggestion: will be cleared and re-used

...

IOCTL handler.

Although this method will reserve a fixed chunk of memory for GetQuote requests during the init time, it is preferable to the

The reservation isn't just during the init time. The reservation is for the lifetime of the driver.

I think I can remove the "during the init time" part.

...

alternative choice of allocating/freeing the shared buffer in the TDX_CMD_GET_QUOTE IOCTL handler, which will damage the direct map.

Why does allocation during the ioctl damage the direct map and allocation on init doesn't?> I would suggest rephrasing to say that you're avoiding multiple bookkeeping round-trips with the VMM for direct map updates.

How about the following?

Although this method reserves a fixed chunk of memory for GetQuote requests, such one-time allocation is preferable to the alternative choice of repeatedly allocating/freeing the shared buffer in the TDX_CMD_GET_QUOTE IOCTL handler, which will damage the direct map (because the sharing/unsharing process modifies the direct map). This allocation model is similar to that used by the AMD SEV guest driver.

...

Reviewed-by: Tony Luck tony.luck@intel.com Reviewed-by: Andi Kleen ak@linux.intel.com Reviewed-by: Mika Westerberg mika.westerberg@linux.intel.com Acked-by: Kirill A. Shutemov kirill.shutemov@linux.intel.com Signed-off-by: Kuppuswamy Sathyanarayanan sathyanarayanan.kuppuswamy@linux.intel.com

---

Changes since v1:

• Removed platform bus device support.
• Instead of allocating the shared buffers using DMA APIs in IOCTL handler, allocated it once in tdx_guest_init() and re-used it in GetQuote IOCTL handler.
• To simplify the design, removed the support for parallel GetQuote requests. It can be added when there is a real requirement for it.
• Fixed commit log and comments to reflect the latest changes.

Documentation/virt/coco/tdx-guest.rst | 11 ++ arch/x86/coco/tdx/tdx.c | 40 ++++++ arch/x86/include/asm/tdx.h | 2 + drivers/virt/coco/tdx-guest/tdx-guest.c | 168 +++++++++++++++++++++++- include/uapi/linux/tdx-guest.h | 43 ++++++ 5 files changed, 263 insertions(+), 1 deletion(-)

diff --git a/Documentation/virt/coco/tdx-guest.rst b/Documentation/virt/coco/tdx-guest.rst index 46e316db6bb4..54601dcd5864 100644 --- a/Documentation/virt/coco/tdx-guest.rst +++ b/Documentation/virt/coco/tdx-guest.rst @@ -42,6 +42,17 @@ ABI. However, in the future, if the TDX Module supports more than one subtype, a new IOCTL CMD will be created to handle it. To keep the IOCTL naming consistent, a subtype index is added as part of the IOCTL CMD.

+2.2 TDX_CMD_GET_QUOTE +----------------------

+:Input parameters: struct tdx_quote_req +:Output: Return 0 on success, -EIO on TDCALL failure or standard error number

•     on common failures. Upon successful execution, QUOTE data is copied
  

•     to tdx_quote_req.buf.
  

+The TDX_CMD_GET_QUOTE IOCTL can be used by attestation software to generate +QUOTE for the given TDREPORT using TDG.VP.VMCALL<GetQuote> hypercall.

Reference

diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c index 26f6e2eaf5c8..09b5925eec67 100644 --- a/arch/x86/coco/tdx/tdx.c +++ b/arch/x86/coco/tdx/tdx.c @@ -33,6 +33,7 @@ #define TDVMCALL_MAP_GPA 0x10001 #define TDVMCALL_REPORT_FATAL_ERROR 0x10003 #define TDVMCALL_SETUP_NOTIFY_INTR 0x10004 +#define TDVMCALL_GET_QUOTE 0x10002

/* MMIO direction */ #define EPT_READ 0 @@ -198,6 +199,45 @@ static void __noreturn tdx_panic(const char *msg) __tdx_hypercall(&args, 0); }

+/**

• • tdx_hcall_get_quote() - Wrapper to request TD Quote using GetQuote

• •                     hypercall.
    

• • @tdquote: Address of the direct mapped shared kernel buffer which

• •      contains TDREPORT data. The same buffer will be used by
    

• •      VMM to store the generated TD Quote output.
    

• • @size: size of the tdquote buffer.
• • Refer to section titled "TDG.VP.VMCALL<GetQuote>" in the TDX GHCI
• • v1.0 specification for more information on GetQuote hypercall.
• • It is used in the TDX guest driver module to get the TD Quote.
• • Return 0 on success or error code on failure.
• */

+int tdx_hcall_get_quote(u8 *tdquote, size_t size) +{

•   struct tdx_hypercall_args args = {0};
  

•   /*
  

•    * TDX guest driver is the only user of this function and it uses
  

•    * the kernel mapped memory. So use virt_to_phys() to get the
  

•    * physical address of the TDQuote buffer without any additional
  

•    * checks for memory type.
  

•    */
  

•   args.r10 = TDX_HYPERCALL_STANDARD;
  

•   args.r11 = TDVMCALL_GET_QUOTE;
  

•   args.r12 = cc_mkdec(virt_to_phys(tdquote));
  

•   args.r13 = size;
  

•   /*
  

•    * Pass the physical address of TDREPORT to the VMM and
  

•    * trigger the Quote generation. It is not a blocking
  

•    * call, hence completion of this request will be notified to
  

•    * the TD guest via a callback interrupt.
  

•    */
  

•   return __tdx_hypercall(&args, 0);
  

+} +EXPORT_SYMBOL_GPL(tdx_hcall_get_quote);

static void tdx_parse_tdinfo(u64 *cc_mask) { struct tdx_module_output out; diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h index 8807fe1b1f3f..a72bd7b96564 100644 --- a/arch/x86/include/asm/tdx.h +++ b/arch/x86/include/asm/tdx.h @@ -75,6 +75,8 @@ int tdx_register_event_irq_cb(tdx_event_irq_cb_t handler, void *data);

int tdx_unregister_event_irq_cb(tdx_event_irq_cb_t handler, void *data);

+int tdx_hcall_get_quote(u8 *tdquote, size_t size);

#else

static inline void tdx_early_init(void) { }; diff --git a/drivers/virt/coco/tdx-guest/tdx-guest.c b/drivers/virt/coco/tdx-guest/tdx-guest.c index 5e44a0fa69bd..a275d6b55f33 100644 --- a/drivers/virt/coco/tdx-guest/tdx-guest.c +++ b/drivers/virt/coco/tdx-guest/tdx-guest.c @@ -12,12 +12,105 @@ #include <linux/mod_devicetable.h> #include <linux/string.h> #include <linux/uaccess.h> +#include <linux/set_memory.h>

#include <uapi/linux/tdx-guest.h>

#include <asm/cpu_device_id.h> #include <asm/tdx.h>

+#define GET_QUOTE_MAX_SIZE (4 * PAGE_SIZE)

+/**

• • struct quote_entry - Quote request struct
• • @valid: Flag to check validity of the GetQuote request.
• • @buf: Kernel buffer to share data with VMM (size is page aligned).
• • @buf_len: Size of the buf in bytes.
• • @compl: Completion object to track completion of GetQuote request.
• */

+struct quote_entry {

•   bool valid;
  

•   void *buf;
  

•   size_t buf_len;
  

•   struct completion compl;
  

+};

+/* Quote data entry */ +static struct quote_entry *qentry;

+/* Lock to streamline quote requests */ +static DEFINE_MUTEX(quote_lock);

+static int quote_cb_handler(void *dev_id) +{

•   struct quote_entry *entry = dev_id;
  

•   struct tdx_quote_hdr *quote_hdr = entry->buf;
  

•   if (entry->valid && quote_hdr->status != GET_QUOTE_IN_FLIGHT)
  

•           complete(&entry->compl);
  

•   return 0;
  

+}

+static void free_shared_pages(void *buf, size_t len) +{

•   unsigned int count = PAGE_ALIGN(len) >> PAGE_SHIFT;
  

•   if (!buf)
  

•           return;
  

•   set_memory_encrypted((unsigned long)buf, count);
  

•   __free_pages(virt_to_page(buf), get_order(len));
  

+}

+static void *alloc_shared_pages(size_t len) +{

•   unsigned int count = PAGE_ALIGN(len) >> PAGE_SHIFT;
  

•   struct page *page;
  

•   int ret;
  

•   page = alloc_pages(GFP_KERNEL, get_order(len));
  

•   if (!page)
  

•           return NULL;
  

•   ret = set_memory_decrypted((unsigned long)page_address(page), count);
  

•   if (ret) {
  

•           __free_pages(page, get_order(len));
  

•           return NULL;
  

•   }
  

•   return page_address(page);
  

+}

+static struct quote_entry *alloc_quote_entry(size_t len) +{

•   struct quote_entry *entry = NULL;
  

•   size_t new_len = PAGE_ALIGN(len);
  

•   entry = kmalloc(sizeof(*entry), GFP_KERNEL);
  

•   if (!entry)
  

•           return NULL;
  

•   entry->buf = alloc_shared_pages(new_len);
  

•   if (!entry->buf) {
  

•           kfree(entry);
  

•           return NULL;
  

•   }
  

•   entry->buf_len = new_len;
  

•   init_completion(&entry->compl);
  

•   entry->valid = false;
  

•   return entry;
  

+}

+static void free_quote_entry(struct quote_entry *entry) +{

•   free_shared_pages(entry->buf, entry->buf_len);
  

•   kfree(entry);
  

+}

static long tdx_get_report0(struct tdx_report_req __user *req) { u8 *reportdata, *tdreport; @@ -53,12 +146,59 @@ static long tdx_get_report0(struct tdx_report_req __user *req) return ret; }

+static long tdx_get_quote(struct tdx_quote_req __user *ureq) +{

•   struct tdx_quote_req req;
  

•   long ret;
  

•   if (copy_from_user(&req, ureq, sizeof(req)))
  

•           return -EFAULT;
  

•   mutex_lock(&quote_lock);
  

•   if (!req.len || req.len > qentry->buf_len) {
  

•           ret = -EINVAL;
  

•           goto quote_failed;
  

•   }
  

Since the qentry is reused across calls, I think you need to clear it out before repopulating it with maybe less data:

memset(qentry->buf, 0, qentry->buf_len)

Good point. I will fix it.

I'm not particularly clear on why there is a length though, since the buffer should always be a TDREPORT_STRUCT. I guess version updates could expand the size.

Since ABI cannot be changed, added it to handle future changes.

...

•   if (copy_from_user(qentry->buf, (void __user *)req.buf, req.len)) {
  

•           ret = -EFAULT;
  

•           goto quote_failed;
  

•   }
  

•   qentry->valid = true;
  

Is the valid field used anywhere? I only see it written and never read.

It is used in quote_cb_handler().

On Wed, 2023-04-12 at 20:41 -0700, Kuppuswamy Sathyanarayanan wrote:

In TDX guest, the second stage in attestation process is to send the TDREPORT to QE/QGS to generate the TD Quote. For platforms that does not support communication channels like vsock or TCP/IP, implement support to get TD Quote using hypercall. GetQuote hypercall can be used by the TD guest to request VMM facilitate the Quote generation via QE/QGS. More details about GetQuote hypercall can be found in TDX Guest-Host Communication Interface (GHCI) for Intel TDX 1.0, section titled "TDG.VP.VMCALL<GetQuote>".

When this patch gets merged, the patch to get the TDREPORT would be long before this patch. To help the git blamers to understand more easily, I think it's better to provide some background here.

FYI below:

" In TDX attestation, the TDREPORT of a TDX guest contains information to uniquely identify the TDX guest along with the TEE environment of the local machine. TDREPORT is integrity-protected and can only be verified on the local machine.

To support TDX remote attestation, in SGX-based attestation, after the TDX guest gets the TDREPORT from the TDX module, the TDREPORT needs to be sent to the SGX Quoting Enclave (QE) to convert it to a remote verifiable Quote.

SGX QE can only run outside of the TDX guest (i.e. in a host process or in a normal VM). For security concern the TDX guest may not support normal communication channels like vsock or TCP/IP. To support remote attestation for such case, TDX uses GetQuote TDVMCALL to ask the host VMM to communicate with the SGX QE. More details about GetQuote TDVMCALL can be found in ... "

Add support for TDX_CMD_GET_QUOTE IOCTL to allow attestation agent submit GetQuote requests from the user space using GetQuote hypercall.

Since GetQuote is an asynchronous request hypercall, VMM will use callback interrupt vector configured by SetupEventNotifyInterrupt hypercall to notify the guest about Quote generation completion or failure. So register an IRQ handler for it.

GetQuote TDVMCALL requires TD guest pass a 4K aligned shared buffer with TDREPORT data as input, which is further used by the VMM to copy the TD Quote result after successful Quote generation. To create the shared buffer, allocate the required memory using alloc_pages() and mark it shared using set_memory_decrypted() in tdx_guest_init().

Personally I think you don't need to mention "using alloc_pages() ... set_memory_decrypted()" staff. They belong to details and the code can tell.

This buffer will be re-used for GetQuote requests in TDX_CMD_GET_QUOTE IOCTL handler.

Besides the "re-used" part, I think it's better to explain the rational of choosing a fixed 16K (4 pages) shared buffer. For instance, in practice in Intel's SGX QE implementation a Quote is less than 8K, and 16K should be big enough in the foreseeable future even considering 3rd party's own implementation.

Also, I guess it's better to call out somewhere currently we don't support multiple GetQuote in parallel because of <xxx>, so allocating a single shared buffer at early time is OK.

Although this method will reserve a fixed chunk of memory for GetQuote requests during the init time, it is preferable to the alternative choice of allocating/freeing the shared buffer in the TDX_CMD_GET_QUOTE IOCTL handler, which will damage the direct map.

Reviewed-by: Tony Luck tony.luck@intel.com Reviewed-by: Andi Kleen ak@linux.intel.com Reviewed-by: Mika Westerberg mika.westerberg@linux.intel.com Acked-by: Kirill A. Shutemov kirill.shutemov@linux.intel.com Signed-off-by: Kuppuswamy Sathyanarayanan sathyanarayanan.kuppuswamy@linux.intel.com

---

Changes since v1:

• Removed platform bus device support.
• Instead of allocating the shared buffers using DMA APIs in IOCTL handler, allocated it once in tdx_guest_init() and re-used it in GetQuote IOCTL handler.
• To simplify the design, removed the support for parallel GetQuote requests. It can be added when there is a real requirement for it.
• Fixed commit log and comments to reflect the latest changes.

Documentation/virt/coco/tdx-guest.rst | 11 ++ arch/x86/coco/tdx/tdx.c | 40 ++++++ arch/x86/include/asm/tdx.h | 2 + drivers/virt/coco/tdx-guest/tdx-guest.c | 168 +++++++++++++++++++++++- include/uapi/linux/tdx-guest.h | 43 ++++++ 5 files changed, 263 insertions(+), 1 deletion(-)

diff --git a/Documentation/virt/coco/tdx-guest.rst b/Documentation/virt/coco/tdx-guest.rst index 46e316db6bb4..54601dcd5864 100644 --- a/Documentation/virt/coco/tdx-guest.rst +++ b/Documentation/virt/coco/tdx-guest.rst @@ -42,6 +42,17 @@ ABI. However, in the future, if the TDX Module supports more than one subtype, a new IOCTL CMD will be created to handle it. To keep the IOCTL naming consistent, a subtype index is added as part of the IOCTL CMD. +2.2 TDX_CMD_GET_QUOTE +----------------------

+:Input parameters: struct tdx_quote_req +:Output: Return 0 on success, -EIO on TDCALL failure or standard error number

•     on common failures. Upon successful execution, QUOTE data is copied
  

•     to tdx_quote_req.buf.
  

+The TDX_CMD_GET_QUOTE IOCTL can be used by attestation software to generate +QUOTE for the given TDREPORT using TDG.VP.VMCALL<GetQuote> hypercall.

Here QUOTE is used, but I see 'Quote' is used in changelog and the code as well, perhaps we need to make sure the consistency.

Reference

diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c index 26f6e2eaf5c8..09b5925eec67 100644 --- a/arch/x86/coco/tdx/tdx.c +++ b/arch/x86/coco/tdx/tdx.c @@ -33,6 +33,7 @@ #define TDVMCALL_MAP_GPA 0x10001 #define TDVMCALL_REPORT_FATAL_ERROR 0x10003 #define TDVMCALL_SETUP_NOTIFY_INTR 0x10004 +#define TDVMCALL_GET_QUOTE 0x10002 /* MMIO direction */ #define EPT_READ 0 @@ -198,6 +199,45 @@ static void __noreturn tdx_panic(const char *msg) __tdx_hypercall(&args, 0); } +/**

• • tdx_hcall_get_quote() - Wrapper to request TD Quote using GetQuote

• •                     hypercall.
    

• • @tdquote: Address of the direct mapped shared kernel buffer which

• •     contains TDREPORT data. The same buffer will be used by
    

• •     VMM to store the generated TD Quote output.
    

• • @size: size of the tdquote buffer.
• • Refer to section titled "TDG.VP.VMCALL<GetQuote>" in the TDX GHCI
• • v1.0 specification for more information on GetQuote hypercall.
• • It is used in the TDX guest driver module to get the TD Quote.
• • Return 0 on success or error code on failure.
• */

+int tdx_hcall_get_quote(u8 *tdquote, size_t size) +{

• struct tdx_hypercall_args args = {0};
• /*

• * TDX guest driver is the only user of this function and it uses
  

• * the kernel mapped memory. So use virt_to_phys() to get the
  

• * physical address of the TDQuote buffer without any additional
  

• * checks for memory type.
  

• */
  

How about just call out this function requires the buffer must be shared in kdoc style comment above this function? We should just focus on what this function is doing.

• args.r10 = TDX_HYPERCALL_STANDARD;
• args.r11 = TDVMCALL_GET_QUOTE;
• args.r12 = cc_mkdec(virt_to_phys(tdquote));
• args.r13 = size;
• /*

• * Pass the physical address of TDREPORT to the VMM and
  

• * trigger the Quote generation. It is not a blocking
  

• * call, hence completion of this request will be notified to
  

• * the TD guest via a callback interrupt.
  

• */
  

• return __tdx_hypercall(&args, 0);

+} +EXPORT_SYMBOL_GPL(tdx_hcall_get_quote);

static void tdx_parse_tdinfo(u64 *cc_mask) { struct tdx_module_output out; diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h index 8807fe1b1f3f..a72bd7b96564 100644 --- a/arch/x86/include/asm/tdx.h +++ b/arch/x86/include/asm/tdx.h @@ -75,6 +75,8 @@ int tdx_register_event_irq_cb(tdx_event_irq_cb_t handler, void *data); int tdx_unregister_event_irq_cb(tdx_event_irq_cb_t handler, void *data); +int tdx_hcall_get_quote(u8 *tdquote, size_t size);

#else static inline void tdx_early_init(void) { }; diff --git a/drivers/virt/coco/tdx-guest/tdx-guest.c b/drivers/virt/coco/tdx-guest/tdx-guest.c index 5e44a0fa69bd..a275d6b55f33 100644 --- a/drivers/virt/coco/tdx-guest/tdx-guest.c +++ b/drivers/virt/coco/tdx-guest/tdx-guest.c @@ -12,12 +12,105 @@ #include <linux/mod_devicetable.h> #include <linux/string.h> #include <linux/uaccess.h> +#include <linux/set_memory.h> #include <uapi/linux/tdx-guest.h> #include <asm/cpu_device_id.h> #include <asm/tdx.h> +#define GET_QUOTE_MAX_SIZE (4 * PAGE_SIZE)

A comment to explain why this particular size is chosen would be helpful.

+/**

• • struct quote_entry - Quote request struct
• • @valid: Flag to check validity of the GetQuote request.
• • @buf: Kernel buffer to share data with VMM (size is page aligned).
• • @buf_len: Size of the buf in bytes.
• • @compl: Completion object to track completion of GetQuote request.
• */

+struct quote_entry {

• bool valid;
• void *buf;
• size_t buf_len;
• struct completion compl;

+};

We have a static global @qentry below.

The buffer size is a fixed size (16K), why do we need @buf_len here?

And why do we need @valid? It seems ...

+/* Quote data entry */ +static struct quote_entry *qentry;

+/* Lock to streamline quote requests */ +static DEFINE_MUTEX(quote_lock);

+static int quote_cb_handler(void *dev_id) +{

• struct quote_entry *entry = dev_id;
• struct tdx_quote_hdr *quote_hdr = entry->buf;
• if (entry->valid && quote_hdr->status != GET_QUOTE_IN_FLIGHT)

• complete(&entry->compl);
  

... this handler is only called when we have received the notification from the VMM, so the VMM must have already put something into the buffer, meaning the buffer is already valid.

Could you explain why do we need @valid?

That being said, to me I found the 'struct quote_entry' itself is quite unnecessary. It looks like a leftover that you didn't remove when changing from supporting multiple GetQuote requests in parallel to only supporting one request at one time.

• return 0;

+}

+static void free_shared_pages(void *buf, size_t len) +{

• unsigned int count = PAGE_ALIGN(len) >> PAGE_SHIFT;
• if (!buf)

• return;
  

Looks like a NULL @buf cannot happen. Use WARN_ON_ONCE()?

• set_memory_encrypted((unsigned long)buf, count);
• __free_pages(virt_to_page(buf), get_order(len));

+}

+static void *alloc_shared_pages(size_t len) +{

• unsigned int count = PAGE_ALIGN(len) >> PAGE_SHIFT;
• struct page *page;
• int ret;
• page = alloc_pages(GFP_KERNEL, get_order(len));
• if (!page)

• return NULL;
  

• ret = set_memory_decrypted((unsigned long)page_address(page), count);
• if (ret) {

• __free_pages(page, get_order(len));
  

• return NULL;
  

• }
• return page_address(page);

+}

I think you can use alloc_pages_exact():

1) For 4 pages it doesn't matter, but in case in the future we want a non-power- of-2 size alloc_pages_exact() can save some memory.

2) It gives you a kernel virtual address directly, so you can save the page_address() call above.

+static struct quote_entry *alloc_quote_entry(size_t len) +{

• struct quote_entry *entry = NULL;
• size_t new_len = PAGE_ALIGN(len);

I don't think you need @new_len, because anyway alloc_shared_pages() will allocate enough space if you just pass @len?

• entry = kmalloc(sizeof(*entry), GFP_KERNEL);
• if (!entry)

• return NULL;
  

• entry->buf = alloc_shared_pages(new_len);
• if (!entry->buf) {

• kfree(entry);
  

• return NULL;
  

• }
• entry->buf_len = new_len;
• init_completion(&entry->compl);
• entry->valid = false;
• return entry;

+}

+static void free_quote_entry(struct quote_entry *entry) +{

• free_shared_pages(entry->buf, entry->buf_len);
• kfree(entry);

+}

static long tdx_get_report0(struct tdx_report_req __user *req) { u8 *reportdata, *tdreport; @@ -53,12 +146,59 @@ static long tdx_get_report0(struct tdx_report_req __user *req) return ret; } +static long tdx_get_quote(struct tdx_quote_req __user *ureq) +{

• struct tdx_quote_req req;
• long ret;
• if (copy_from_user(&req, ureq, sizeof(req)))

• return -EFAULT;
  

• mutex_lock(&quote_lock);
• if (!req.len || req.len > qentry->buf_len) {

• ret = -EINVAL;
  

• goto quote_failed;
  

• }
• if (copy_from_user(qentry->buf, (void __user *)req.buf, req.len)) {

• ret = -EFAULT;
  

• goto quote_failed;
  

• }
• qentry->valid = true;
• reinit_completion(&qentry->compl);
• /* Submit GetQuote Request using GetQuote hypercall */
• ret = tdx_hcall_get_quote(qentry->buf, qentry->buf_len);
• if (ret) {

• pr_err("GetQuote hypercall failed, status:%lx\n", ret);
  

• ret = -EIO;
  

• goto quote_failed;
  

• }
• /* Wait till GetQuote completion */
• wait_for_completion(&qentry->compl);

Non-killable wait w/o timeout worries me a little bit, because it can wait forever if VMM also couldn't get the Quote for whatever reason and doesn't have it's own timeout.  Unfortunately the GHCI doesn't put any requirement to the VMM on this, so we kinda depend on the VMM.

Perhaps for now it's OK to have this simple implementation, but looks we should at least call out the risk in the comment.

• if (copy_to_user((void __user *)req.buf, qentry->buf, req.len))

• ret = -EFAULT;
  

+quote_failed:

• qentry->valid = false;
• mutex_unlock(&quote_lock);
• return ret;

+}

static long tdx_guest_ioctl(struct file *file, unsigned int cmd, unsigned long arg) { switch (cmd) { case TDX_CMD_GET_REPORT0: return tdx_get_report0((struct tdx_report_req __user *)arg);

• case TDX_CMD_GET_QUOTE:

• return tdx_get_quote((struct tdx_quote_req *)arg);
  

  default: return -ENOTTY; }

@@ -84,15 +224,41 @@ MODULE_DEVICE_TABLE(x86cpu, tdx_guest_ids); static int __init tdx_guest_init(void) {

• int ret;
• if (!x86_match_cpu(tdx_guest_ids)) return -ENODEV;

• return misc_register(&tdx_misc_dev);

• ret = misc_register(&tdx_misc_dev);
• if (ret)

• return ret;
  

• qentry = alloc_quote_entry(GET_QUOTE_MAX_SIZE);
• if (!qentry) {

• pr_err("Quote entry allocation failed\n");
  

This is a rather confusing message from user's perspective. The result of this error isn't clear from this message. I think we should have clear message ...

• ret = -ENOMEM;
  

• goto free_misc;
  

• }
• ret = tdx_register_event_irq_cb(quote_cb_handler, qentry);
• if (ret)

• goto free_quote;
  

• return 0;

+free_quote:

• free_quote_entry(qentry);

+free_misc:

• misc_deregister(&tdx_misc_dev);

... here saying something like "Attestation is not available" so user can be clear about this.

• return ret;

} module_init(tdx_guest_init); static void __exit tdx_guest_exit(void) {

• tdx_unregister_event_irq_cb(quote_cb_handler, qentry);
• free_quote_entry(qentry); misc_deregister(&tdx_misc_dev);

} module_exit(tdx_guest_exit); diff --git a/include/uapi/linux/tdx-guest.h b/include/uapi/linux/tdx-guest.h index a6a2098c08ff..500cdfa025ad 100644 --- a/include/uapi/linux/tdx-guest.h +++ b/include/uapi/linux/tdx-guest.h @@ -17,6 +17,12 @@ /* Length of TDREPORT used in TDG.MR.REPORT TDCALL */ #define TDX_REPORT_LEN 1024 +/* TD Quote status codes */ +#define GET_QUOTE_SUCCESS 0 +#define GET_QUOTE_IN_FLIGHT 0xffffffffffffffff +#define GET_QUOTE_ERROR 0x8000000000000000 +#define GET_QUOTE_SERVICE_UNAVAILABLE 0x8000000000000001

/**

• struct tdx_report_req - Request struct for TDX_CMD_GET_REPORT0 IOCTL.

@@ -30,6 +36,35 @@ struct tdx_report_req { __u8 tdreport[TDX_REPORT_LEN]; }; +/* struct tdx_quote_hdr: Format of Quote request buffer header.

• • @version: Quote format version, filled by TD.
• • @status: Status code of Quote request, filled by VMM.
• • @in_len: Length of TDREPORT, filled by TD.
• • @out_len: Length of Quote data, filled by VMM.
• • @data: Quote data on output or TDREPORT on input.
• • More details of Quote data header can be found in TDX
• • Guest-Host Communication Interface (GHCI) for Intel TDX 1.0,
• • section titled "TDG.VP.VMCALL<GetQuote>"
• */

+struct tdx_quote_hdr {

• __u64 version;
• __u64 status;
• __u32 in_len;
• __u32 out_len;
• __u64 data[];

+};

This structure is weird. It's a header, but it contains the dynamic-size buffer. If you have __data[] in this structure, then it is already a buffer for the entire Quote, no? Then should we just call it 'struct tdx_quote'?

Or do you want to remove __data[]?

+/* struct tdx_quote_req: Request struct for TDX_CMD_GET_QUOTE IOCTL.

• • @buf: Address of user buffer that includes TDREPORT. Upon successful

• • completion of IOCTL, output is copied back to the same buffer.
    

This description isn't precise. "user buffer that includes TDREPORT" doesn't tell application writer where to put the TDREPORT at all. We need to explicitly call out the buffer starts with 'tdx_quote_hdr' followed by TDREPORT immediately.

• • @len: Length of the Quote buffer.
• */

+struct tdx_quote_req {

• __u64 buf;
• __u64 len;

+};

/*

• TDX_CMD_GET_REPORT0 - Get TDREPORT0 (a.k.a. TDREPORT subtype 0) using

•                   TDCALL[TDG.MR.REPORT]
  

@@ -39,4 +74,12 @@ struct tdx_report_req { */ #define TDX_CMD_GET_REPORT0 _IOWR('T', 1, struct tdx_report_req) +/*

• • TDX_CMD_GET_QUOTE - Get TD Guest Quote from QE/QGS using GetQuote

• •        TDVMCALL.
    

• • Returns 0 on success or standard errno on other failures.
• */

+#define TDX_CMD_GET_QUOTE _IOR('T', 2, struct tdx_quote_req)

#endif /* _UAPI_LINUX_TDX_GUEST_H_ */

On Sun, 2023-04-30 at 23:03 -0700, Sathyanarayanan Kuppuswamy wrote:

Hi Kai,

On 4/28/23 6:49 AM, Huang, Kai wrote:

...

On Wed, 2023-04-12 at 20:41 -0700, Kuppuswamy Sathyanarayanan wrote:

...

In TDX guest, the second stage in attestation process is to send the TDREPORT to QE/QGS to generate the TD Quote. For platforms that does not support communication channels like vsock or TCP/IP, implement support to get TD Quote using hypercall. GetQuote hypercall can be used by the TD guest to request VMM facilitate the Quote generation via QE/QGS. More details about GetQuote hypercall can be found in TDX Guest-Host Communication Interface (GHCI) for Intel TDX 1.0, section titled "TDG.VP.VMCALL<GetQuote>".

When this patch gets merged, the patch to get the TDREPORT would be long before this patch. To help the git blamers to understand more easily, I think it's better to provide some background here.

FYI below:

" In TDX attestation, the TDREPORT of a TDX guest contains information to uniquely identify the TDX guest along with the TEE environment of the local machine. TDREPORT is integrity-protected and can only be verified on the local machine.

To support TDX remote attestation, in SGX-based attestation, after the TDX guest gets the TDREPORT from the TDX module, the TDREPORT needs to be sent to the SGX Quoting Enclave (QE) to convert it to a remote verifiable Quote.

SGX QE can only run outside of the TDX guest (i.e. in a host process or in a normal VM). For security concern the TDX guest may not support normal communication channels like vsock or TCP/IP. To support remote attestation for such case, TDX uses GetQuote TDVMCALL to ask the host VMM to communicate with the SGX QE. More details about GetQuote TDVMCALL can be found in ... "

Ok. I will add some introduction to the commit log.

...

...

Add support for TDX_CMD_GET_QUOTE IOCTL to allow attestation agent submit GetQuote requests from the user space using GetQuote hypercall.

Since GetQuote is an asynchronous request hypercall, VMM will use callback interrupt vector configured by SetupEventNotifyInterrupt hypercall to notify the guest about Quote generation completion or failure. So register an IRQ handler for it.

GetQuote TDVMCALL requires TD guest pass a 4K aligned shared buffer with TDREPORT data as input, which is further used by the VMM to copy the TD Quote result after successful Quote generation. To create the shared buffer, allocate the required memory using alloc_pages() and mark it shared using set_memory_decrypted() in tdx_guest_init().

Personally I think you don't need to mention "using alloc_pages() ... set_memory_decrypted()" staff. They belong to details and the code can tell.

...

This buffer will be re-used for GetQuote requests in TDX_CMD_GET_QUOTE IOCTL handler.

Besides the "re-used" part, I think it's better to explain the rational of choosing a fixed 16K (4 pages) shared buffer. For instance, in practice in Intel's SGX QE implementation a Quote is less than 8K, and 16K should be big enough in the foreseeable future even considering 3rd party's own implementation.

I will add it part of the comment in the code.

...

Also, I guess it's better to call out somewhere currently we don't support multiple GetQuote in parallel because of <xxx>, so allocating a single shared buffer at early time is OK.

...

...

Although this method will reserve a fixed chunk of memory for GetQuote requests during the init time, it is preferable to the alternative choice of allocating/freeing the shared buffer in the TDX_CMD_GET_QUOTE IOCTL handler, which will damage the direct map.

Updated commit log looks like below:

In TDX guest, the attestation process is used to verify the TDX guest
trustworthiness to other entities before provisioning secrets to the
guest. The First step in the attestation process is TDREPORT
generation, which involves getting the guest measurement data in the
format of TDREPORT, which is further used to validate the authenticity
of the TDX guest. TDREPORT by design is integrity-protected and can
only be verified on the local machine.

To support remote verification of the TDREPORT (in a SGX-based attestation), the TDREPORT needs to be sent to the SGX Quoting Enclave (QE) to convert it to a remote verifiable Quote. SGX QE by design can only run outside of the TDX guest (i.e. in a host process or in a normal VM) and the guest can use communication channels like vsock or TCP/IP to send the TDREPORT to the QE. But for security concerns, some platforms may not support these communication channels. To handle such

"platforms may not support vsock/tcp/ip etc" isn't correct. It should be the "TDX guest" may not support those.

The security concern mainly is about the CSP doesn't want to expose vsock/tcp/ip to TDX guest to allow it to be able to communicate to host service (Quoting service in our example) directly. However the host will almost certainly support at least tcp/ip otherwise the machine is totally isolated.

cases, TDX defines a GetQuote hypercall which can be used by the guest
to request the host VMM to communicate with the SGX QE. More details
about GetQuote hypercall can be found in TDX Guest-Host Communication
Interface (GHCI) for Intel TDX 1.0, section titled
"TDG.VP.VMCALL<GetQuote>".

Add support for TDX_CMD_GET_QUOTE IOCTL to allow an attestation agent to submit GetQuote requests from the user space using GetQuote hypercall. Since GetQuote is an asynchronous request hypercall, VMM will use the callback interrupt vector configured by the SetupEventNotifyInterrupt hypercall to notify the guest about Quote generation completion or failure. So register an IRQ handler for it. GetQuote TDVMCALL requires TD guest pass a 4K aligned shared buffer with TDREPORT data as input, which is further used by the VMM to copy the TD Quote result after successful Quote generation. Allocate the required shared memory once in tdx_guest_init() and reuse it in the

"required" isn't very clear IMHO, because there's no mention of any requirement at all regarding to the buffer size. If you don't want to explain in changelog, perhaps you need to at least mention something like "allocate a large enough shared memory" etc.

TDX_CMD_GET_QUOTE IOCTL handler for GetQuote requests.

Although this method reserves a fixed chunk of memory for GetQuote requests, such one-time allocation is preferable to the alternative choice of repeatedly allocating/freeing the shared buffer in the TDX_CMD_GET_QUOTE IOCTL handler, which will damage the direct map (because the sharing/unsharing process modifies the direct map). This allocation model is similar to that used by the AMD SEV guest driver. Since the Quote generation process is not time-critical or frequently used, the current version do not support parallel GetQuote requests.

^ does not

[...]

...

...

diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c index 26f6e2eaf5c8..09b5925eec67 100644 --- a/arch/x86/coco/tdx/tdx.c +++ b/arch/x86/coco/tdx/tdx.c @@ -33,6 +33,7 @@ #define TDVMCALL_MAP_GPA 0x10001 #define TDVMCALL_REPORT_FATAL_ERROR 0x10003 #define TDVMCALL_SETUP_NOTIFY_INTR 0x10004 +#define TDVMCALL_GET_QUOTE 0x10002 /* MMIO direction */ #define EPT_READ 0 @@ -198,6 +199,45 @@ static void __noreturn tdx_panic(const char *msg) __tdx_hypercall(&args, 0); } +/**

• • tdx_hcall_get_quote() - Wrapper to request TD Quote using GetQuote

• •                     hypercall.
    

• • @tdquote: Address of the direct mapped shared kernel buffer which

• •     contains TDREPORT data. The same buffer will be used by
    

• •     VMM to store the generated TD Quote output.
    

• • @size: size of the tdquote buffer.

Better to call out @size must be in granularity of 4K.

...

...

• • Refer to section titled "TDG.VP.VMCALL<GetQuote>" in the TDX GHCI
• • v1.0 specification for more information on GetQuote hypercall.
• • It is used in the TDX guest driver module to get the TD Quote.
• • Return 0 on success or error code on failure.
• */

+int tdx_hcall_get_quote(u8 *tdquote, size_t size) +{

• struct tdx_hypercall_args args = {0};
• /*

• * TDX guest driver is the only user of this function and it uses
  

• * the kernel mapped memory. So use virt_to_phys() to get the
  

• * physical address of the TDQuote buffer without any additional
  

• * checks for memory type.
  

• */
  

How about just call out this function requires the buffer must be shared in kdoc style comment above this function? We should just focus on what this function is doing.

It was suggested in the previous review to add it. A comment about why using virt_to_phys() is fine here.

Sorry tried to dig but I couldn't find the comment you mentioned.

Anyway, IMHO you can just remove this comment, because after reading again, in fact IMHO it only confuses people:

1) "memory type" is confusing. I think I (as someone who is working on TDX too) understand by "memory type" you actually mean the virtual address is from kernel direct mapping, or it could be from vmalloc()/vmap() (do you?), but for others it could be cache related memory type (UC, WB, etc).

2) You already said the buffer is "direct mapped shared kernel buffer" (btw, should be "directly mapped" really) in the comment which explains @tdquote, thus it's clear how to get the physical address. "TDX guest driver is the only user of this function" doesn't matter -- when there's another user in the future and if it changes where the @tdquote comes from, then the comment of @tdquote and the code needs to be updated anyway.

So I don't see any good of this comment.

Btw, to me @tdquote isn't a good name because it gives me the impression that the Quote is used as input. How about just 'buf' (which you also used in 'tdx_quote_req' structure)?

...

...

• args.r10 = TDX_HYPERCALL_STANDARD;
• args.r11 = TDVMCALL_GET_QUOTE;
• args.r12 = cc_mkdec(virt_to_phys(tdquote));

Btw can we just use __pa()? To be honest I am ignorant on the difference between virt_to_phys() and __pa(), i.e. when should we use which.

Also, you _may_ want to add a comment why "cc_mkdec()" is used. By the nature of this TDVMCALL, it's obvious the buffer needs to be shared, and the VMM must check whether the buffer is actually shared, no matter whether the "shared-bit" is set here or not.

So to me it's just requested by the GHCI spec that we need to include the "shared-bit", but it _seems_ the GHCI spec doesn't explicitly say we need to do that because it only says "Shared buffer as input". So looks a comment can help to clarify a little bit.

...

...

• args.r13 = size;

The @size must be 4K-aligned per GHCI. I guess we should add a check and return early rather than depending on the TDVMCALL to fail?

...

...

• /*

• * Pass the physical address of TDREPORT to the VMM and
  

• * trigger the Quote generation. It is not a blocking
  

• * call, hence completion of this request will be notified to
  

• * the TD guest via a callback interrupt.
  

• */
  

• return __tdx_hypercall(&args, 0);

+} +EXPORT_SYMBOL_GPL(tdx_hcall_get_quote);

[...]

...

...

+/**

• • struct quote_entry - Quote request struct
• • @valid: Flag to check validity of the GetQuote request.
• • @buf: Kernel buffer to share data with VMM (size is page aligned).
• • @buf_len: Size of the buf in bytes.
• • @compl: Completion object to track completion of GetQuote request.
• */

+struct quote_entry {

• bool valid;
• void *buf;
• size_t buf_len;
• struct completion compl;

+};

We have a static global @qentry below.

The buffer size is a fixed size (16K), why do we need @buf_len here?

I have added it to support buf length changes in future (like adding a command line option to allow user change the GET_QUOTE_MAX_SIZE). Also, IMO, using buf_len is more readable than just using GET_QUOTE_MAX_SIZE macro in all places.

...

And why do we need @valid? It seems ...

As a precaution against spurious event notification. I also believe that in the future, event notification IRQs may be used for other purposes such as vTPM or other TDVMCALL services, and that this handler may be triggered without a valid GetQuote request. So, before we process the IRQ, I want to make sure we have a valid buffer.

OK. This is an shared IRQ basically, so we need to track whether we have any GetQuote request pending.

However I am wondering whether we need a dedicated @valid for this purpose. If I read correctly, we will make sure the buffer is zero-ed when there's no request pending, thus can we just use some member in 'tdx_quote_hdr' to track?

For instance, per-GHCI the 'version' must be set to 1 for a valid request. And I think in a foreseeable future we can also assume @in_len being the size of TDREPORT_STRUCT. Can we use one of them (i.e. version) for this purpose?

...

...

+/* Quote data entry */ +static struct quote_entry *qentry;

+/* Lock to streamline quote requests */ +static DEFINE_MUTEX(quote_lock);

+static int quote_cb_handler(void *dev_id) +{

• struct quote_entry *entry = dev_id;
• struct tdx_quote_hdr *quote_hdr = entry->buf;
• if (entry->valid && quote_hdr->status != GET_QUOTE_IN_FLIGHT)

• complete(&entry->compl);
  

... this handler is only called when we have received the notification from the VMM, so the VMM must have already put something into the buffer, meaning the buffer is already valid.

Could you explain why do we need @valid?

That being said, to me I found the 'struct quote_entry' itself is quite unnecessary. It looks like a leftover that you didn't remove when changing from supporting multiple GetQuote requests in parallel to only supporting one request at one time.

I don't want to use multiple global values. So I have bundled all Quote related book keeping (completion object or buffer pointer) in the same struct.

IMHO both @buf_len and @valid are not necessary, so you just need a static buffer plus a static completion. And you already have a static @quote_lock.

But no very strong opinion here..

[...]

...

...

• /* Submit GetQuote Request using GetQuote hypercall */
• ret = tdx_hcall_get_quote(qentry->buf, qentry->buf_len);
• if (ret) {

• pr_err("GetQuote hypercall failed, status:%lx\n", ret);
  

• ret = -EIO;
  

• goto quote_failed;
  

• }
• /* Wait till GetQuote completion */
• wait_for_completion(&qentry->compl);

Non-killable wait w/o timeout worries me a little bit, because it can wait forever if VMM also couldn't get the Quote for whatever reason and doesn't have it's own timeout.  Unfortunately the GHCI doesn't put any requirement to the VMM on this, so we kinda depend on the VMM.

Perhaps for now it's OK to have this simple implementation, but looks we should at least call out the risk in the comment.

How about the following comment?

/*

• Since TDX GHCI specification does not define a valid timeout for GetQuote
• requests, wait until VMM sends the completion notification. Note that there
• is a risk that this wait can be infinite.

*/

This comment is missing the point I think.

There are two things actually:

1) The timeout from VMM

The GHCI should explicitly put some requirement on the VMM, i.e. say something like "the VMM must not wait for the Quote infinitely but must signal the TDX guest after a certain time, which can be implementation specific". In this case, we can be sure that the guest won't wait forever.

2) The timeout support in the GetQuote itself

This allows the guest to specify a timeout in the GetQuote TDVMCALL, so guest can have its own control on how long to wait.

AFAICT for now we don't have requirement on 2). What we truly want is 1), because we certainly don't want to wait forever because of some careless VMM implementation.

So, how about:

/* * Although the GHCI doesn't specifically put a hard requirement on the * VMM that it must not wait for the Quote infinitely, a sane VMM should * always notify the guest after a certain time no matter whether * getting the Quote is successful or not. For now just depend on the * VMM to do so. */

[...]

...

...

static int __init tdx_guest_init(void) {

• int ret;
• if (!x86_match_cpu(tdx_guest_ids)) return -ENODEV;

• return misc_register(&tdx_misc_dev);

• ret = misc_register(&tdx_misc_dev);
• if (ret)

• return ret;
  

• qentry = alloc_quote_entry(GET_QUOTE_MAX_SIZE);
• if (!qentry) {

• pr_err("Quote entry allocation failed\n");
  

This is a rather confusing message from user's perspective. The result of this error isn't clear from this message. I think we should have clear message ...

I will remove it.

I think it's fine to keep it, but my point is, besides above error msg, it's better to explicitly print "attestation is not available", which is the result of above error, to the user.

Whether the above message can be improved is another story. For instance, I believe "Failed to allocate Quote buffer" is better.

...

...

• ret = -ENOMEM;
  

• goto free_misc;
  

• }
• ret = tdx_register_event_irq_cb(quote_cb_handler, qentry);
• if (ret)

• goto free_quote;
  

• return 0;

+free_quote:

• free_quote_entry(qentry);

+free_misc:

• misc_deregister(&tdx_misc_dev);

... here saying something like "Attestation is not available" so user can be clear about this.

...

• return ret;

} module_init(tdx_guest_init); static void __exit tdx_guest_exit(void) {

• tdx_unregister_event_irq_cb(quote_cb_handler, qentry);
• free_quote_entry(qentry); misc_deregister(&tdx_misc_dev);

} module_exit(tdx_guest_exit); diff --git a/include/uapi/linux/tdx-guest.h b/include/uapi/linux/tdx-guest.h index a6a2098c08ff..500cdfa025ad 100644 --- a/include/uapi/linux/tdx-guest.h +++ b/include/uapi/linux/tdx-guest.h @@ -17,6 +17,12 @@ /* Length of TDREPORT used in TDG.MR.REPORT TDCALL */ #define TDX_REPORT_LEN 1024 +/* TD Quote status codes */ +#define GET_QUOTE_SUCCESS 0 +#define GET_QUOTE_IN_FLIGHT 0xffffffffffffffff +#define GET_QUOTE_ERROR 0x8000000000000000 +#define GET_QUOTE_SERVICE_UNAVAILABLE 0x8000000000000001

/**

• struct tdx_report_req - Request struct for TDX_CMD_GET_REPORT0 IOCTL.

@@ -30,6 +36,35 @@ struct tdx_report_req { __u8 tdreport[TDX_REPORT_LEN]; }; +/* struct tdx_quote_hdr: Format of Quote request buffer header.

• • @version: Quote format version, filled by TD.
• • @status: Status code of Quote request, filled by VMM.
• • @in_len: Length of TDREPORT, filled by TD.
• • @out_len: Length of Quote data, filled by VMM.
• • @data: Quote data on output or TDREPORT on input.
• • More details of Quote data header can be found in TDX
• • Guest-Host Communication Interface (GHCI) for Intel TDX 1.0,
• • section titled "TDG.VP.VMCALL<GetQuote>"
• */

+struct tdx_quote_hdr {

• __u64 version;
• __u64 status;
• __u32 in_len;
• __u32 out_len;
• __u64 data[];

+};

This structure is weird. It's a header, but it contains the dynamic-size buffer. If you have __data[] in this structure, then it is already a buffer for the entire Quote, no? Then should we just call it 'struct tdx_quote'?

Or do you want to remove __data[]?

I can name it as struct tdx_quote_data

If go with route, why not just 'tdx_quote', or 'tdx_tdquote'?

Or, actually I think 'tdx_quote' (or 'tdx_tdquote') seems to be the format of the _true_ Quote, so perhaps we want 'struct tdx_quote_req_buf'?

...

...

+/* struct tdx_quote_req: Request struct for TDX_CMD_GET_QUOTE IOCTL.

• • @buf: Address of user buffer that includes TDREPORT. Upon successful

• • completion of IOCTL, output is copied back to the same buffer.
    

This description isn't precise. "user buffer that includes TDREPORT" doesn't tell application writer where to put the TDREPORT at all. We need to explicitly call out the buffer starts with 'tdx_quote_hdr' followed by TDREPORT immediately.

I have specified it in struct tdx_quote_hdr.data help content.

Perhaps I missed something but I didn't say at any place this is clearly documented. The comment around @data above certainly doesn't.

Just say something like:

@buf: The userspace pointer which points to the 'struct tdx_quote_req_buf' (whatever the final name)

...

...

• • @len: Length of the Quote buffer.
• */

+struct tdx_quote_req {

• __u64 buf;
• __u64 len;

+};

/*

Hi,

On 4/26/23 8:47 AM, Dionna Amalie Glaze wrote:

On Wed, Apr 12, 2023 at 8:42 PM Kuppuswamy Sathyanarayanan sathyanarayanan.kuppuswamy@linux.intel.com wrote:

...

In TDX guest, the second stage of the attestation process is Quote generation. This process is required to convert the locally generated TDREPORT into a remotely verifiable Quote. It involves sending the TDREPORT data to a Quoting Enclave (QE) which will verify the integerity of the TDREPORT and sign it with an attestation key.

nit: integrity

...

Intel's TDX attestation driver exposes TDX_CMD_GET_QUOTE IOCTL to allow user agent get the TD Quote.

nit: to get

...

Add a kernel selftest module to verify the Quote generation feature.

TD Quote generation involves following steps:

• Get the TDREPORT data using TDX_CMD_GET_REPORT IOCTL.
• Embed the TDREPORT data in quote buffer and request for quote generation via TDX_CMD_GET_QUOTE IOCTL request.
• Upon completion of the GetQuote request, check for non zero value in the status field of Quote header to make sure the generated quote is valid.

Reviewed-by: Tony Luck tony.luck@intel.com Reviewed-by: Andi Kleen ak@linux.intel.com Reviewed-by: Shuah Khan skhan@linuxfoundation.org Reviewed-by: Mika Westerberg mika.westerberg@linux.intel.com Acked-by: Kirill A. Shutemov kirill.shutemov@linux.intel.com Signed-off-by: Kuppuswamy Sathyanarayanan sathyanarayanan.kuppuswamy@linux.intel.com

---

tools/testing/selftests/tdx/tdx_guest_test.c | 68 ++++++++++++++++++-- 1 file changed, 62 insertions(+), 6 deletions(-)

diff --git a/tools/testing/selftests/tdx/tdx_guest_test.c b/tools/testing/selftests/tdx/tdx_guest_test.c index 81d8cb88ea1a..2eccde54185b 100644 --- a/tools/testing/selftests/tdx/tdx_guest_test.c +++ b/tools/testing/selftests/tdx/tdx_guest_test.c @@ -18,6 +18,7 @@ #define TDX_GUEST_DEVNAME "/dev/tdx_guest" #define HEX_DUMP_SIZE 8 #define DEBUG 0 +#define QUOTE_SIZE 8192

/**

• struct tdreport_type - Type header of TDREPORT_STRUCT.

@@ -128,21 +129,29 @@ static void print_array_hex(const char *title, const char *prefix_str, printf("\n"); }

+/* Helper function to get TDREPORT */ +long get_tdreport0(int devfd, struct tdx_report_req *req) +{

•   int i;
  

•   /* Generate sample report data */
  

•   for (i = 0; i < TDX_REPORTDATA_LEN; i++)
  

•           req->reportdata[i] = i;
  

Shouldn't req be zeroed before populating reportdata? We wouldn't want uninitialized memory to leave the guest. I know this is just a test,

There are only two members in struct tdx_report_req (reportdata and tdreport). The reportdata has already been updated here, and the tdreport will be updated by the kernel on output. Since TDX_CMD_GET_REPORT0 IOCTL handler uses an intermediate kernel buffer to the TDREPORT and copies the generated report back to this user buffer, this uninitialized tdreport data never leaves the guest.

IMO, we don't need to zero it. However, because it is harmless, I am fine with including it.

but it's best to model good practices for anyone that might copy/paste.

...

•   return ioctl(devfd, TDX_CMD_GET_REPORT0, req);
  

+}

TEST(verify_report) { struct tdx_report_req req; struct tdreport *tdreport;

•   int devfd, i;
  

•   int devfd;
  
    devfd = open(TDX_GUEST_DEVNAME, O_RDWR | O_SYNC);
    ASSERT_LT(0, devfd);
  
  

•   /* Generate sample report data */
  

•   for (i = 0; i < TDX_REPORTDATA_LEN; i++)
  

•           req.reportdata[i] = i;
  

•   /* Get TDREPORT */
  

•   ASSERT_EQ(0, ioctl(devfd, TDX_CMD_GET_REPORT0, &req));
  

•   ASSERT_EQ(0, get_tdreport0(devfd, &req));
  
    if (DEBUG) {
            print_array_hex("\n\t\tTDX report data\n", "",
  

@@ -160,4 +169,51 @@ TEST(verify_report) ASSERT_EQ(0, close(devfd)); }

+TEST(verify_quote) +{

•   struct tdx_quote_hdr *quote_hdr;
  

•   struct tdx_report_req rep_req;
  

•   struct tdx_quote_req req;
  

•   __u64 quote_buf_size;
  

•   __u8 *quote_buf;
  

•   int devfd;
  

•   /* Open attestation device */
  

•   devfd = open(TDX_GUEST_DEVNAME, O_RDWR | O_SYNC);
  

•   ASSERT_LT(0, devfd);
  

•   /* Add size for quote header */
  

•   quote_buf_size = sizeof(*quote_hdr) + QUOTE_SIZE;
  

•   /* Allocate quote buffer */
  

•   quote_buf = malloc(quote_buf_size);
  

•   ASSERT_NE(NULL, quote_buf);
  

•   quote_hdr = (struct tdx_quote_hdr *)quote_buf;
  

•   /* Initialize GetQuote header */
  

•   quote_hdr->version = 1;
  

•   quote_hdr->status  = GET_QUOTE_SUCCESS;
  

•   quote_hdr->in_len  = TDX_REPORT_LEN;
  

•   quote_hdr->out_len = 0;
  

•   /* Get TDREPORT data */
  

•   ASSERT_EQ(0, get_tdreport0(devfd, &rep_req));
  

•   /* Fill GetQuote request */
  

•   memcpy(quote_hdr->data, rep_req.tdreport, TDX_REPORT_LEN);
  

•   req.buf   = (__u64)quote_buf;
  

•   req.len   = quote_buf_size;
  

•   ASSERT_EQ(0, ioctl(devfd, TDX_CMD_GET_QUOTE, &req));
  

•   /* Check whether GetQuote request is successful */
  

•   EXPECT_EQ(0, quote_hdr->status);
  

•   free(quote_buf);
  

•   ASSERT_EQ(0, close(devfd));
  

+}

TEST_HARNESS_MAIN

2.34.1