Re: [PATCH v4 09/24] x86/virt/seamldr: Check update limit before TDX Module updates

[Yan Zhao]

On Thu, Feb 12, 2026 at 06:35:12AM -0800, Chao Gao wrote:
> TDX maintains a log about each TDX Module which has been loaded. This
> log has a finite size which limits the number of TDX Module updates
> which can be performed.
> 
> After each successful update, the remaining updates reduces by one. Once
> it reaches zero, further updates will fail until next reboot.
> 
> Before updating the TDX Module, verify that the update limit has not been
> exceeded. Otherwise, P-SEAMLDR will detect this violation after the old TDX
> Module is gone and all TDs will be killed.
> 
> Note that userspace should perform this check before updates. Perform this
> check in kernel as well to make the update process more robust.
> 
> Signed-off-by: Chao Gao <chao.gao@xxxxxxxxx>
> Reviewed-by: Tony Lindgren <tony.lindgren@xxxxxxxxxxxxxxx>
> ---
>  arch/x86/virt/vmx/tdx/seamldr.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/arch/x86/virt/vmx/tdx/seamldr.c b/arch/x86/virt/vmx/tdx/seamldr.c
> index 694243f1f220..733b13215691 100644
> --- a/arch/x86/virt/vmx/tdx/seamldr.c
> +++ b/arch/x86/virt/vmx/tdx/seamldr.c
> @@ -52,6 +52,16 @@ EXPORT_SYMBOL_FOR_MODULES(seamldr_get_info, "tdx-host");
>   */
>  int seamldr_install_module(const u8 *data, u32 size)
>  {
> +	struct seamldr_info info;
> +	int ret;
> +
> +	ret = seamldr_get_info(&info);
> +	if (ret)
> +		return ret;
> +
> +	if (!info.num_remaining_updates)
> +		return -ENOSPC;
seamldr_install_module() is invoked by tdx_fw_write().
Why don't we put the check of info.num_remaining_updates in tdx_fw_prepare()?

>  	if (WARN_ON_ONCE(!is_vmalloc_addr(data)))
>  		return -EINVAL;
>  
> -- 
> 2.47.3
> 
>