Hi All,
In TDX guest, the attestation process is used to verify the TDX guest
trustworthiness to other entities before provisioning secrets to the
guest.
The TDX guest attestation process consists of two steps:
1. TDREPORT generation
2. Quote generation.
The First step (TDREPORT generation) involves getting the TDX guest
measurement data in the format of TDREPORT which is further used to
validate the authenticity of the TDX guest. The second step involves
sending the TDREPORT to a Quoting Enclave (QE) server to generate a
remotely verifiable Quote. TDREPORT by design can only be verified on
the local platform. To support remote verification of the TDREPORT,
TDX leverages Intel SGX Quoting Enclave to verify the TDREPORT
locally and convert it to a remotely verifiable Quote. Although
attestation software can use communication methods like TCP/IP or
vsock to send the TDREPORT to QE, not all platforms support these
communication models. So TDX GHCI specification [1] defines a method
for Quote generation via hypercalls. Please check the discussion from
Google [2] and Alibaba [3] which clarifies the need for hypercall based
Quote generation support. This patch set adds this support.
Support for TDREPORT generation already exists in the TDX guest driver.
This patchset extends the same driver to add the Quote generation
support.
Following are the details of the patch set:
Patch 1/3 -> Adds event notification IRQ support.
Patch 2/3 -> Adds Quote generation support.
Patch 3/3 -> Adds selftest support for Quote generation feature.
[1] https://cdrdv2.intel.com/v1/dl/getContent/726790, section titled "TDG.VP.VMCALL<GetQuote>".
[2] https://lore.kernel.org/lkml/CAAYXXYxxs2zy_978GJDwKfX5Hud503gPc8=1kQ-+JwG_kA79mg@mail.gmail.com/
[3] https://lore.kernel.org/lkml/[email protected]/
Kuppuswamy Sathyanarayanan (3):
x86/tdx: Add TDX Guest event notify interrupt support
virt: tdx-guest: Add Quote generation support
selftests/tdx: Test GetQuote TDX attestation feature
Documentation/virt/coco/tdx-guest.rst | 11 +
arch/x86/coco/tdx/tdx.c | 203 +++++++++++++++
arch/x86/include/asm/tdx.h | 8 +
drivers/virt/coco/tdx-guest/tdx-guest.c | 249 ++++++++++++++++++-
include/uapi/linux/tdx-guest.h | 44 ++++
tools/testing/selftests/tdx/tdx_guest_test.c | 68 ++++-
6 files changed, 575 insertions(+), 8 deletions(-)
--
2.34.1
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>".
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 without breaking the direct map, use DMA alloc APIs.
Also note that, shared buffer allocation is currently handled in IOCTL
handler, although it will increase the TDX_CMD_GET_QUOTE IOCTL response
time, it is negligible compared to the time required for the quote
generation completion. So IOCTL performance optimization is not
considered at this time.
To support parallel GetQuote requests, use linked list to track the
active GetQuote requests and upon receiving the callback IRQ, loop
through the active requests and mark the processed requests complete.
Users can open multiple instances of the attestation device and send
GetQuote requests in parallel.
Since GetQuote support requires usage of DMA APIs, convert TDX guest
driver to a platform driver.
Reviewed-by: Tony Luck <[email protected]>
Reviewed-by: Andi Kleen <[email protected]>
Reviewed-by: Mika Westerberg <[email protected]>
Acked-by: Kirill A. Shutemov <[email protected]>
Signed-off-by: Kuppuswamy Sathyanarayanan <[email protected]>
---
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 | 249 +++++++++++++++++++++++-
include/uapi/linux/tdx-guest.h | 44 +++++
5 files changed, 344 insertions(+), 2 deletions(-)
diff --git a/Documentation/virt/coco/tdx-guest.rst b/Documentation/virt/coco/tdx-guest.rst
index 46e316db6bb4..69954ed85c68 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, -EINTR for interrupted request, -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 d03985952d45..b823c4f493d4 100644
--- a/arch/x86/coco/tdx/tdx.c
+++ b/arch/x86/coco/tdx/tdx.c
@@ -34,6 +34,7 @@
#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
@@ -199,6 +200,45 @@ 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 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..2424a0d02bc8 100644
--- a/drivers/virt/coco/tdx-guest/tdx-guest.c
+++ b/drivers/virt/coco/tdx-guest/tdx-guest.c
@@ -12,12 +12,151 @@
#include <linux/mod_devicetable.h>
#include <linux/string.h>
#include <linux/uaccess.h>
+#include <linux/platform_device.h>
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <linux/dma-mapping.h>
#include <uapi/linux/tdx-guest.h>
#include <asm/cpu_device_id.h>
#include <asm/tdx.h>
+/**
+ * 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.
+ * @dma_address: DMA address of the buffer.
+ * @dev: Reference to device used in DMA allocation.
+ * @compl: Completion object to track completion of GetQuote request.
+ * @list: List object for reference in quote_list.
+ */
+struct quote_entry {
+ bool valid;
+ void *buf;
+ size_t buf_len;
+ dma_addr_t dma_address;
+ struct device *dev;
+ struct completion compl;
+ struct list_head list;
+};
+
+/*
+ * To support parallel GetQuote requests, use the list
+ * to track active GetQuote requests.
+ */
+static LIST_HEAD(quote_list);
+
+/* Lock to protect quote_list */
+static DEFINE_MUTEX(quote_lock);
+
+/* Quote generation work */
+static void quote_callback_handler(struct work_struct *work);
+
+static DECLARE_WORK(quote_work, quote_callback_handler);
+
+static struct platform_device *tdx_dev;
+
+static struct quote_entry *alloc_quote_entry(struct device *dev, size_t buf_len)
+{
+ struct quote_entry *entry = NULL;
+ size_t new_len = PAGE_ALIGN(buf_len);
+
+ entry = kmalloc(sizeof(*entry), GFP_KERNEL);
+ if (!entry)
+ return NULL;
+
+ entry->buf = dma_alloc_coherent(dev, new_len, &entry->dma_address,
+ GFP_KERNEL);
+ if (!entry->buf) {
+ kfree(entry);
+ return NULL;
+ }
+
+ entry->buf_len = new_len;
+ init_completion(&entry->compl);
+ entry->valid = true;
+ entry->dev = dev;
+
+ return entry;
+}
+
+static void free_quote_entry(struct quote_entry *entry)
+{
+ dma_free_coherent(entry->dev, entry->buf_len, entry->buf,
+ entry->dma_address);
+ kfree(entry);
+}
+
+/* Must be called with quote_lock held */
+static void _del_quote_entry(struct quote_entry *entry)
+{
+ list_del(&entry->list);
+ free_quote_entry(entry);
+}
+
+static void del_quote_entry(struct quote_entry *entry)
+{
+ mutex_lock("e_lock);
+ _del_quote_entry(entry);
+ mutex_unlock("e_lock);
+}
+
+/* Handles early termination of GetQuote requests */
+static void terminate_quote_request(struct quote_entry *entry)
+{
+ struct tdx_quote_hdr *quote_hdr;
+
+ /*
+ * For early termination, if the request is not yet
+ * processed by VMM (GET_QUOTE_IN_FLIGHT), the VMM
+ * still owns the shared buffer, so mark the request
+ * invalid to let quote_callback_handler() handle the
+ * memory cleanup function. If the request is already
+ * processed, then do the cleanup and return.
+ */
+ mutex_lock("e_lock);
+ quote_hdr = entry->buf;
+ if (quote_hdr->status == GET_QUOTE_IN_FLIGHT) {
+ entry->valid = false;
+ mutex_unlock("e_lock);
+ return;
+ }
+ _del_quote_entry(entry);
+ mutex_unlock("e_lock);
+}
+
+static int attestation_callback_handler(void *dev_id)
+{
+ schedule_work("e_work);
+ return 0;
+}
+
+static void quote_callback_handler(struct work_struct *work)
+{
+ struct tdx_quote_hdr *quote_hdr;
+ struct quote_entry *entry, *next;
+
+ /* Find processed quote request and mark it complete */
+ mutex_lock("e_lock);
+ list_for_each_entry_safe(entry, next, "e_list, list) {
+ quote_hdr = entry->buf;
+ if (quote_hdr->status == GET_QUOTE_IN_FLIGHT)
+ continue;
+ /*
+ * If user invalidated the current request, remove the
+ * entry from the quote list and free it. If the request
+ * is still valid, mark it complete.
+ */
+ if (entry->valid)
+ complete(&entry->compl);
+ else
+ _del_quote_entry(entry);
+ }
+ mutex_unlock("e_lock);
+}
+
static long tdx_get_report0(struct tdx_report_req __user *req)
{
u8 *reportdata, *tdreport;
@@ -53,12 +192,78 @@ 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 device *dev = &tdx_dev->dev;
+ struct quote_entry *entry;
+ struct tdx_quote_req req;
+ long ret;
+
+ if (copy_from_user(&req, ureq, sizeof(req)))
+ return -EFAULT;
+
+ /*
+ * TDX GHCI specification does not specify any upper limit
+ * on Quote buffer size. So no upper limit check is added.
+ * If a user passes a large value, it is expected that it
+ * will fail during memory allocation in alloc_quote_entry().
+ */
+ if (!req.len)
+ return -EINVAL;
+
+ entry = alloc_quote_entry(dev, req.len);
+ if (!entry)
+ return -ENOMEM;
+
+ if (copy_from_user(entry->buf, (void __user *)req.buf, req.len)) {
+ free_quote_entry(entry);
+ return -EFAULT;
+ }
+
+ mutex_lock("e_lock);
+
+ /* Submit GetQuote Request using GetQuote hypercall */
+ ret = tdx_hcall_get_quote(entry->buf, entry->buf_len);
+ if (ret) {
+ mutex_unlock("e_lock);
+ dev_err(dev, "GetQuote hypercall failed, status:%lx\n", ret);
+ free_quote_entry(entry);
+ return -EIO;
+ }
+
+ /* Add current quote entry to quote_list to track active requests */
+ list_add_tail(&entry->list, "e_list);
+
+ mutex_unlock("e_lock);
+
+ /*
+ * Wait till GetQuote completion or request is cancelled by the
+ * user signal. If the request is cancelled by the user, don't
+ * cleanup the quote buffer as it is still owned by the VMM.
+ */
+ ret = wait_for_completion_interruptible(&entry->compl);
+ if (ret < 0) {
+ dev_err(dev, "GetQuote request terminated\n");
+ terminate_quote_request(entry);
+ return -EINTR;
+ }
+
+ if (copy_to_user((void __user *)req.buf, entry->buf, req.len))
+ ret = -EFAULT;
+
+ del_quote_entry(entry);
+
+ 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;
}
@@ -76,6 +281,27 @@ static struct miscdevice tdx_misc_dev = {
.fops = &tdx_guest_fops,
};
+static int tdx_guest_probe(struct platform_device *pdev)
+{
+ if (tdx_register_event_irq_cb(attestation_callback_handler, pdev))
+ return -EIO;
+
+ return misc_register(&tdx_misc_dev);
+}
+
+static int tdx_guest_remove(struct platform_device *pdev)
+{
+ tdx_unregister_event_irq_cb(attestation_callback_handler, pdev);
+ misc_deregister(&tdx_misc_dev);
+ return 0;
+}
+
+static struct platform_driver tdx_guest_driver = {
+ .probe = tdx_guest_probe,
+ .remove = tdx_guest_remove,
+ .driver.name = KBUILD_MODNAME,
+};
+
static const struct x86_cpu_id tdx_guest_ids[] = {
X86_MATCH_FEATURE(X86_FEATURE_TDX_GUEST, NULL),
{}
@@ -84,16 +310,35 @@ 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 = platform_driver_register(&tdx_guest_driver);
+ if (ret) {
+ pr_err("failed to register driver, err=%d\n", ret);
+ return ret;
+ }
+
+ tdx_dev = platform_device_register_simple(KBUILD_MODNAME,
+ PLATFORM_DEVID_NONE,
+ NULL, 0);
+ if (IS_ERR(tdx_dev)) {
+ ret = PTR_ERR(tdx_dev);
+ pr_err("failed to allocate device, err=%d\n", ret);
+ platform_driver_unregister(&tdx_guest_driver);
+ return ret;
+ }
+
+ return 0;
}
module_init(tdx_guest_init);
static void __exit tdx_guest_exit(void)
{
- misc_deregister(&tdx_misc_dev);
+ platform_device_unregister(tdx_dev);
+ platform_driver_unregister(&tdx_guest_driver);
}
module_exit(tdx_guest_exit);
diff --git a/include/uapi/linux/tdx-guest.h b/include/uapi/linux/tdx-guest.h
index a6a2098c08ff..94c78d08f2aa 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[];
+};
+
+/* 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.
+ * @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 +74,13 @@ 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, -EINTR for interrupted request, and
+ * standard errno on other failures.
+ */
+#define TDX_CMD_GET_QUOTE _IOR('T', 2, struct tdx_quote_req)
+
#endif /* _UAPI_LINUX_TDX_GUEST_H_ */
--
2.34.1
On Sat, Mar 25, 2023 at 11:20:38PM -0700, Kuppuswamy Sathyanarayanan wrote:
> Since GetQuote support requires usage of DMA APIs, convert TDX guest
> driver to a platform driver.
Sorry, but that's not a valid reason to use a platform device for fake
things like this:
> +static struct platform_device *tdx_dev;
Especially a single static one.
> +static int tdx_guest_probe(struct platform_device *pdev)
> +{
> + if (tdx_register_event_irq_cb(attestation_callback_handler, pdev))
> + return -EIO;
> +
> + return misc_register(&tdx_misc_dev);
> +}
> +
> +static int tdx_guest_remove(struct platform_device *pdev)
> +{
> + tdx_unregister_event_irq_cb(attestation_callback_handler, pdev);
> + misc_deregister(&tdx_misc_dev);
> + return 0;
> +}
> +
> +static struct platform_driver tdx_guest_driver = {
> + .probe = tdx_guest_probe,
> + .remove = tdx_guest_remove,
> + .driver.name = KBUILD_MODNAME,
> +};
> +
> static const struct x86_cpu_id tdx_guest_ids[] = {
> X86_MATCH_FEATURE(X86_FEATURE_TDX_GUEST, NULL),
> {}
> @@ -84,16 +310,35 @@ 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 = platform_driver_register(&tdx_guest_driver);
> + if (ret) {
> + pr_err("failed to register driver, err=%d\n", ret);
> + return ret;
> + }
No, please do not create a fake platform driver.
> + tdx_dev = platform_device_register_simple(KBUILD_MODNAME,
> + PLATFORM_DEVID_NONE,
> + NULL, 0);
And please do not create a fake platform device.
As always, do not create fake platform devices for things that are NOT
platform devices.
If this device needs DMA (but why?) then make it a real device and tie
it to the bus it belongs to (that it is obviously doing DMA on.)
But as-is, this isn't ok, sorry.
thanks,
greg k-h
Hi Greg,
Thanks for the review comments.
On 3/25/23 11:34 PM, Greg KH wrote:
> On Sat, Mar 25, 2023 at 11:20:38PM -0700, Kuppuswamy Sathyanarayanan wrote:
>> Since GetQuote support requires usage of DMA APIs, convert TDX guest
>> driver to a platform driver.
>
> Sorry, but that's not a valid reason to use a platform device for fake
> things like this:
>
>> +static struct platform_device *tdx_dev;
>
> Especially a single static one.
>
>> +static int tdx_guest_probe(struct platform_device *pdev)
>> +{
>> + if (tdx_register_event_irq_cb(attestation_callback_handler, pdev))
>> + return -EIO;
>> +
>> + return misc_register(&tdx_misc_dev);
>> +}
>> +
>> +static int tdx_guest_remove(struct platform_device *pdev)
>> +{
>> + tdx_unregister_event_irq_cb(attestation_callback_handler, pdev);
>> + misc_deregister(&tdx_misc_dev);
>> + return 0;
>> +}
>> +
>> +static struct platform_driver tdx_guest_driver = {
>> + .probe = tdx_guest_probe,
>> + .remove = tdx_guest_remove,
>> + .driver.name = KBUILD_MODNAME,
>> +};
>> +
>> static const struct x86_cpu_id tdx_guest_ids[] = {
>> X86_MATCH_FEATURE(X86_FEATURE_TDX_GUEST, NULL),
>> {}
>> @@ -84,16 +310,35 @@ 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 = platform_driver_register(&tdx_guest_driver);
>> + if (ret) {
>> + pr_err("failed to register driver, err=%d\n", ret);
>> + return ret;
>> + }
>
> No, please do not create a fake platform driver.
>
>> + tdx_dev = platform_device_register_simple(KBUILD_MODNAME,
>> + PLATFORM_DEVID_NONE,
>> + NULL, 0);
>
> And please do not create a fake platform device.
>
> As always, do not create fake platform devices for things that are NOT
> platform devices.
>
> If this device needs DMA (but why?) then make it a real device and tie
Since the Quote generation process requires the guest and VMM to share data,
we need to use shared buffers. But in TDX guest, VMM cannot directly access
the guest private memory. Any memory that is required for communication with
the VMM must be shared explicitly. One way is to allocate the memory on
demand and share it explicitly using set_memory_decrypted() call. Although
this approach is clean, since it breaks the direct mapping, it is not
efficient. An alternative way is to reserve a pool of shared buffers during
boot time and re-use them for guest/VMM communication. Since in TDX, DMA API
is configured to tap into the SWIOTLB memory framework (which is shared by
default), we try to use dma_alloc_* APIs to allocate the shared buffers from
the shared pool without breaking the direct map.
If usage of DMA APIs / platform device is not acceptable for this use case,
an alternative approach is to allocate a fixed number of shared buffers during
the TDX guest driver probe and use it for GetQuote requests. Although it would
limit the amount of memory we can use for GetQuote requests at a time and also
reserve a chunk of memory during the init() time, I think it is an acceptable
tradeoff when compared to alternative choices. The AMD SEV guest driver also
adopts the similar approach. Please let me know if this approach is acceptable.
> it to the bus it belongs to (that it is obviously doing DMA on.)
>
> thanks,
>
> greg k-h
--
Sathyanarayanan Kuppuswamy
Linux Kernel Developer
On Sun, Mar 26, 2023 at 12:06:26PM -0700, Sathyanarayanan Kuppuswamy wrote:
> If usage of DMA APIs / platform device is not acceptable for this use case,
It is not ok to use a platform device for this because you just do not
have a platform device for it, don't make one up out of thin air please,
as that really doesn't even have the correct bindings to the DMA memory
that you want here.
> an alternative approach is to allocate a fixed number of shared buffers during
> the TDX guest driver probe and use it for GetQuote requests. Although it would
> limit the amount of memory we can use for GetQuote requests at a time and also
> reserve a chunk of memory during the init() time, I think it is an acceptable
> tradeoff when compared to alternative choices. The AMD SEV guest driver also
> adopts the similar approach. Please let me know if this approach is acceptable.
This sounds like a better approach.
thanks,
greg k-h
On Sat, Mar 25, 2023 at 11:20 PM Kuppuswamy Sathyanarayanan
<[email protected]> wrote:
>
> Hi All,
>
> In TDX guest, the attestation process is used to verify the TDX guest
> trustworthiness to other entities before provisioning secrets to the
> guest.
>
> The TDX guest attestation process consists of two steps:
>
> 1. TDREPORT generation
> 2. Quote generation.
>
> The First step (TDREPORT generation) involves getting the TDX guest
> measurement data in the format of TDREPORT which is further used to
> validate the authenticity of the TDX guest. The second step involves
> sending the TDREPORT to a Quoting Enclave (QE) server to generate a
> remotely verifiable Quote. TDREPORT by design can only be verified on
> the local platform. To support remote verification of the TDREPORT,
> TDX leverages Intel SGX Quoting Enclave to verify the TDREPORT
> locally and convert it to a remotely verifiable Quote. Although
> attestation software can use communication methods like TCP/IP or
> vsock to send the TDREPORT to QE, not all platforms support these
> communication models. So TDX GHCI specification [1] defines a method
> for Quote generation via hypercalls. Please check the discussion from
> Google [2] and Alibaba [3] which clarifies the need for hypercall based
Thanks Sathyanarayanan for submitting patches again.
I just wanted to reiterate what I said before that having a clean
TDVMCALL based interface to get TDX Quote without any virtio/vsock
dependency is critical for us to support many use cases.
+Chong Cai
Adding a colleague per his request since he's not subscribed to the list yet.
On Mon, Mar 27, 2023 at 10:36 AM Erdem Aktas <[email protected]> wrote:
>
> On Sat, Mar 25, 2023 at 11:20 PM Kuppuswamy Sathyanarayanan
> <[email protected]> wrote:
> >
> > Hi All,
> >
> > In TDX guest, the attestation process is used to verify the TDX guest
> > trustworthiness to other entities before provisioning secrets to the
> > guest.
> >
> > The TDX guest attestation process consists of two steps:
> >
> > 1. TDREPORT generation
> > 2. Quote generation.
> >
> > The First step (TDREPORT generation) involves getting the TDX guest
> > measurement data in the format of TDREPORT which is further used to
> > validate the authenticity of the TDX guest. The second step involves
> > sending the TDREPORT to a Quoting Enclave (QE) server to generate a
> > remotely verifiable Quote. TDREPORT by design can only be verified on
> > the local platform. To support remote verification of the TDREPORT,
> > TDX leverages Intel SGX Quoting Enclave to verify the TDREPORT
> > locally and convert it to a remotely verifiable Quote. Although
> > attestation software can use communication methods like TCP/IP or
> > vsock to send the TDREPORT to QE, not all platforms support these
> > communication models. So TDX GHCI specification [1] defines a method
> > for Quote generation via hypercalls. Please check the discussion from
> > Google [2] and Alibaba [3] which clarifies the need for hypercall based
> Thanks Sathyanarayanan for submitting patches again.
>
> I just wanted to reiterate what I said before that having a clean
> TDVMCALL based interface to get TDX Quote without any virtio/vsock
> dependency is critical for us to support many use cases.
--
-Dionna Glaze, PhD (she/her)
On Tue, Mar 28, 2023 at 12:59 PM Dionna Amalie Glaze
<[email protected]> wrote:
>
> +Chong Cai
>
> Adding a colleague per his request since he's not subscribed to the list yet.
>
> On Mon, Mar 27, 2023 at 10:36 AM Erdem Aktas <[email protected]> wrote:
> >
> > On Sat, Mar 25, 2023 at 11:20 PM Kuppuswamy Sathyanarayanan
> > <[email protected]> wrote:
> > >
> > > Hi All,
> > >
> > > In TDX guest, the attestation process is used to verify the TDX guest
> > > trustworthiness to other entities before provisioning secrets to the
> > > guest.
> > >
> > > The TDX guest attestation process consists of two steps:
> > >
> > > 1. TDREPORT generation
> > > 2. Quote generation.
> > >
> > > The First step (TDREPORT generation) involves getting the TDX guest
> > > measurement data in the format of TDREPORT which is further used to
> > > validate the authenticity of the TDX guest. The second step involves
> > > sending the TDREPORT to a Quoting Enclave (QE) server to generate a
> > > remotely verifiable Quote. TDREPORT by design can only be verified on
> > > the local platform. To support remote verification of the TDREPORT,
> > > TDX leverages Intel SGX Quoting Enclave to verify the TDREPORT
> > > locally and convert it to a remotely verifiable Quote. Although
> > > attestation software can use communication methods like TCP/IP or
> > > vsock to send the TDREPORT to QE, not all platforms support these
> > > communication models. So TDX GHCI specification [1] defines a method
> > > for Quote generation via hypercalls. Please check the discussion from
> > > Google [2] and Alibaba [3] which clarifies the need for hypercall based
> > Thanks Sathyanarayanan for submitting patches again.
> >
> > I just wanted to reiterate what I said before that having a clean
> > TDVMCALL based interface to get TDX Quote without any virtio/vsock
> > dependency is critical for us to support many use cases.
>
> +1 to Erdem's point. A simple TDVMCALL interface could make it much
> easier for user cases that can not depend on virtio and vsock.
> Without the TDVMCALL, it will largely limit those user cases to adopt TDX.
> Thanks Sathyanarayanan for submitting this patch.
> --
> -Dionna Glaze, PhD (she/her)