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virt: tdx-guest: Add a helper for the Quote buffer size

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The Quote buffer size is a constant sprinkled across several places.
Read it from a helper instead. And rename the constant to avoid using a
verb.

This sets up the plumbing for a later change that makes the size
dynamic.

There are several "sizes" at play here: the raw Quote data, the Quote
buffer (the header metadata plus the raw data), and the allocation (the
page-padded Quote buffer). The helper returns the Quote buffer size and
leaves page alignment to callers that need it.

AI was used under supervision to collect/apply feedback, review code and
workshop logs.

Signed-off-by: Peter Fang <peter.fang@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://patch.msgid.link/20260930103739.2851980-5-peter.fang@intel.com
This commit is contained in:
Peter Fang 2026-09-30 03:30:53 -07:00 committed by Dave Hansen
parent 683cc6010d
commit ef83bbc05c
1 changed files with 21 additions and 10 deletions
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31
drivers/virt/coco/tdx-guest/tdx-guest.c
View File

@ -162,7 +162,7 @@ static void tdx_mr_deinit(const struct attribute_group *mr_grp)
* DICE-based attestation uses layered evidence that requires * DICE-based attestation uses layered evidence that requires
* larger Quote size (~100K). * larger Quote size (~100K).
*/ */
#define GET_QUOTE_BUF_SIZE SZ_128K #define TDX_DEFAULT_QUOTE_SIZE SZ_128K
#define GET_QUOTE_CMD_VER 1 #define GET_QUOTE_CMD_VER 1
@ -206,26 +206,36 @@ static long tdx_get_report0(struct tdx_report_req __user *req)
USER_SOCKPTR(req->tdreport)); USER_SOCKPTR(req->tdreport));
} }
/* Size of the header metadata plus the largest possible raw Quote. */
static size_t get_quote_buf_size(void)
{
return TDX_DEFAULT_QUOTE_SIZE;
}
static void free_quote_buf(struct tdx_quote_buf *buf) static void free_quote_buf(struct tdx_quote_buf *buf)
{ {
size_t len = PAGE_ALIGN(GET_QUOTE_BUF_SIZE); size_t alloc_size = PAGE_ALIGN(get_quote_buf_size());
unsigned int count = len >> PAGE_SHIFT; unsigned int count;
count = alloc_size >> PAGE_SHIFT;
if (set_memory_encrypted((unsigned long)buf, count)) { if (set_memory_encrypted((unsigned long)buf, count)) {
pr_err("Failed to restore encryption mask for Quote buffer, leak it\n"); pr_err("Failed to restore encryption mask for Quote buffer, leak it\n");
return; return;
} }
free_pages_exact(buf, len); free_pages_exact(buf, alloc_size);
} }
static struct tdx_quote_buf *alloc_quote_buf(void) static struct tdx_quote_buf *alloc_quote_buf(void)
{ {
size_t len = PAGE_ALIGN(GET_QUOTE_BUF_SIZE); size_t alloc_size = PAGE_ALIGN(get_quote_buf_size());
unsigned int count = len >> PAGE_SHIFT;
struct tdx_quote_buf *buf; struct tdx_quote_buf *buf;
unsigned int count;
buf = alloc_pages_exact(len, GFP_KERNEL | __GFP_ZERO); count = alloc_size >> PAGE_SHIFT;
buf = alloc_pages_exact(alloc_size, GFP_KERNEL | __GFP_ZERO);
if (!buf) if (!buf)
return NULL; return NULL;
@ -266,6 +276,7 @@ static int tdx_report_new_locked(struct tsm_report *report)
{ {
u8 *buf; u8 *buf;
struct tsm_report_desc *desc = &report->desc; struct tsm_report_desc *desc = &report->desc;
size_t quote_buf_size = get_quote_buf_size();
u32 out_len; u32 out_len;
int ret; int ret;
u64 err; u64 err;
@ -281,7 +292,7 @@ static int tdx_report_new_locked(struct tsm_report *report)
if (desc->inblob_len != TDX_REPORTDATA_LEN) if (desc->inblob_len != TDX_REPORTDATA_LEN)
return -EINVAL; return -EINVAL;
memset(quote_buf, 0, GET_QUOTE_BUF_SIZE); memset(quote_buf, 0, quote_buf_size);
/* Update Quote buffer header */ /* Update Quote buffer header */
quote_buf->version = GET_QUOTE_CMD_VER; quote_buf->version = GET_QUOTE_CMD_VER;
@ -292,7 +303,7 @@ static int tdx_report_new_locked(struct tsm_report *report)
if (ret) if (ret)
return ret; return ret;
err = tdx_hcall_get_quote(quote_buf, GET_QUOTE_BUF_SIZE); err = tdx_hcall_get_quote(quote_buf, PAGE_ALIGN(quote_buf_size));
if (err) { if (err) {
pr_err("GetQuote hypercall failed, status:%llx\n", err); pr_err("GetQuote hypercall failed, status:%llx\n", err);
return -EIO; return -EIO;
@ -311,7 +322,7 @@ static int tdx_report_new_locked(struct tsm_report *report)
out_len = READ_ONCE(quote_buf->out_len); out_len = READ_ONCE(quote_buf->out_len);
if (struct_size(quote_buf, data, out_len) > GET_QUOTE_BUF_SIZE) if (struct_size(quote_buf, data, out_len) > quote_buf_size)
return -EFBIG; return -EFBIG;
buf = kvmemdup(quote_buf->data, out_len, GFP_KERNEL); buf = kvmemdup(quote_buf->data, out_len, GFP_KERNEL);