Re: [PATCH v2 4/5] x86/virt/tdx: Add extra memory to TDX module for the extensions

[Xu Yilun]

On Wed, Sep 16, 2026 at 03:40:51PM +0800, Chao Gao wrote:
> >+static __init int tdx_ext_mem_setup(void)
> >+{
> >+	unsigned int required_pages = tdx_sysinfo.ext.memory_pool_required_pages;
> >+	struct tdx_hpa_list *hpa_list;
> >+	unsigned int added_pages;
> >+	struct page *page;
> >+	int ret;
> >+
> >+	/*
> >+	 * TDX module uses the metadata memory_pool_required_pages to indicate
> >+	 * how much memory is still needed. This value decreases each time
> >+	 * memory is added via TDH.EXT.MEM.ADD.
> >+	 *
> >+	 * On first time initialization, a value of 0 before any memory is
> >+	 * added is unusual. But host makes no assumptions. Skip the memory
> >+	 * setup and let subsequent steps catch any actual errors.
> >+	 */
> 
> The fact that the value decreases on each TDH.EXT.MEM.ADD is not relevant
> here.
> 
> Also, calling 0 "unusual" does not help the reader. It is either a valid
> value the kernel needs to handle, or an invalid one the kernel can assert
> on.
> 
> How about:
> 	
> 	/*
> 	 * The TDX module may require no memory at all. Skip the memory
> 	 * setup in that case.
> 	 */

Since we will drop ext_required check, I've found a reason why no memory
is required.

	/*
	 * Skip the memory setup if no memory is required. This may happen when
	 * no add-on features requiring TDX module extensions are configured
	 * via TDH.SYS.CONFIG.
	 */

> 
> >+	if (!required_pages)
> >+		return 0;