Re: [PATCH v3 3/4] virt: tdx-guest: Use a variable to store the Quote buffer size

[Kuppuswamy Sathyanarayanan]

On 7/29/2026 5:29 AM, Peter Fang wrote:
> In preparation for dynamic Quote buffer sizes, replace the fixed size

sizes -> size?

> constant with a variable.
> 
> The size is currently a constant sprinkled across several places. Store
> it in a variable and have all the users read it from there.

You are also dropping PAGE_ALIGN() in alloc and free calls. You can
mention it in commit log.

> 
> Signed-off-by: Peter Fang <peter.fang@xxxxxxxxx>
> ---

Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>


> v3:
>  - Split out using a variable for the buffer size from the v2 "Allocate
>    Quote buffer dynamically" patch to refactor first. [Dave]
>  - Pass the buffer size into alloc_quote_buf() by value. [Dave]
>  - Drop the Reviewed-by tags from v2 (Kiryl, Binbin) as the patch was
>    reworked.
> ---
>  drivers/virt/coco/tdx-guest/tdx-guest.c | 22 +++++++++++-----------
>  1 file changed, 11 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/virt/coco/tdx-guest/tdx-guest.c b/drivers/virt/coco/tdx-guest/tdx-guest.c
> index f47c5429d002..3d3f79ab45af 100644
> --- a/drivers/virt/coco/tdx-guest/tdx-guest.c
> +++ b/drivers/virt/coco/tdx-guest/tdx-guest.c
> @@ -191,8 +191,9 @@ struct tdx_quote_buf {
>  	u8 data[];
>  };
>  
> -/* Quote data buffer */
> +/* Quote data buffer and length */
>  static void *quote_data;
> +static size_t quote_data_len;
>  
>  /* Lock to streamline quote requests */
>  static DEFINE_MUTEX(quote_lock);
> @@ -209,9 +210,8 @@ static long tdx_get_report0(struct tdx_report_req __user *req)
>  			     USER_SOCKPTR(req->tdreport));
>  }
>  
> -static void free_quote_buf(void *buf)
> +static void free_quote_buf(void *buf, size_t len)
>  {
> -	size_t len = PAGE_ALIGN(GET_QUOTE_BUF_SIZE);
>  	unsigned int count = len >> PAGE_SHIFT;
>  
>  	if (set_memory_encrypted((unsigned long)buf, count)) {
> @@ -222,9 +222,8 @@ static void free_quote_buf(void *buf)
>  	free_pages_exact(buf, len);
>  }
>  
> -static void *alloc_quote_buf(void)
> +static void *alloc_quote_buf(size_t len)
>  {
> -	size_t len = PAGE_ALIGN(GET_QUOTE_BUF_SIZE);
>  	unsigned int count = len >> PAGE_SHIFT;
>  	void *addr;
>  
> @@ -285,7 +284,7 @@ static int tdx_report_new_locked(struct tsm_report *report, void *data)
>  	if (desc->inblob_len != TDX_REPORTDATA_LEN)
>  		return -EINVAL;
>  
> -	memset(quote_data, 0, GET_QUOTE_BUF_SIZE);
> +	memset(quote_data, 0, quote_data_len);
>  
>  	/* Update Quote buffer header */
>  	quote_buf->version = GET_QUOTE_CMD_VER;
> @@ -296,7 +295,7 @@ static int tdx_report_new_locked(struct tsm_report *report, void *data)
>  	if (ret)
>  		return ret;
>  
> -	err = tdx_hcall_get_quote(quote_data, GET_QUOTE_BUF_SIZE);
> +	err = tdx_hcall_get_quote(quote_data, quote_data_len);
>  	if (err) {
>  		pr_err("GetQuote hypercall failed, status:%llx\n", err);
>  		return -EIO;
> @@ -315,7 +314,7 @@ static int tdx_report_new_locked(struct tsm_report *report, void *data)
>  
>  	out_len = READ_ONCE(quote_buf->out_len);
>  
> -	if (TDX_QUOTE_BUF_LEN(out_len) > GET_QUOTE_BUF_SIZE)
> +	if (TDX_QUOTE_BUF_LEN(out_len) > quote_data_len)
>  		return -EFBIG;
>  
>  	buf = kvmemdup(quote_buf->data, out_len, GFP_KERNEL);
> @@ -417,7 +416,8 @@ static int __init tdx_guest_init(void)
>  	if (ret)
>  		goto deinit_mr;
>  
> -	quote_data = alloc_quote_buf();
> +	quote_data_len = GET_QUOTE_BUF_SIZE;
> +	quote_data = alloc_quote_buf(quote_data_len);
>  	if (!quote_data) {
>  		pr_err("Failed to allocate Quote buffer\n");
>  		ret = -ENOMEM;
> @@ -431,7 +431,7 @@ static int __init tdx_guest_init(void)
>  	return 0;
>  
>  free_quote:
> -	free_quote_buf(quote_data);
> +	free_quote_buf(quote_data, quote_data_len);
>  free_misc:
>  	misc_deregister(&tdx_misc_dev);
>  deinit_mr:
> @@ -444,7 +444,7 @@ module_init(tdx_guest_init);
>  static void __exit tdx_guest_exit(void)
>  {
>  	tsm_report_unregister(&tdx_tsm_ops);
> -	free_quote_buf(quote_data);
> +	free_quote_buf(quote_data, quote_data_len);
>  	misc_deregister(&tdx_misc_dev);
>  	tdx_mr_deinit(tdx_attr_groups[0]);
>  }

-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer