Re: [PATCH v4 04/16] x86/virt/tdx: Allocate page bitmap for Dynamic PAMT

[Edgecombe, Rick P]

On Wed, 2025-12-24 at 17:10 +0800, Xu Yilun wrote:
> Is it better we seal the awkward pattern inside the if (dpamt supported)  block:
> 
> 	if (tdx_support_dynamic_pamt(&tdx_sysinfo))
> 		if (!ret && !(ret = read_sys_metadata_field(0x9100000100000013, &val)))
> 			sysinfo_tdmr->pamt_page_bitmap_entry_bits = val;

The extra indentation might be objectionable.

But I agree that line is too hard to read. It actually already caused some
confusion, which precipitated the comment. I played around with it and was
thinking to go with this instead to make it fit the pattern better. What do you
think?

static int get_tdx_sys_info_dpamt_bits(struct tdx_sys_info_tdmr *sysinfo_tdmr,
u64 *val)
{
	/*
	 * Don't let the metadata reading fail if dynamic PAMT isn't
	 * supported. The TDX code can fallback to normal PAMT in
	 * this case.
	 */
	if (!tdx_supports_dynamic_pamt(&tdx_sysinfo)) {
		*val = 0;
		return 0;
	}

	return read_sys_metadata_field(0x9100000100000013, val);
}

static int get_tdx_sys_info_tdmr(struct tdx_sys_info_tdmr *sysinfo_tdmr)
{
	int ret = 0;
	u64 val;

	if (!ret && !(ret = read_sys_metadata_field(0x9100000100000008, &val)))
		sysinfo_tdmr->max_tdmrs = val;
	if (!ret && !(ret = read_sys_metadata_field(0x9100000100000009, &val)))
		sysinfo_tdmr->max_reserved_per_tdmr = val;
	if (!ret && !(ret = read_sys_metadata_field(0x9100000100000010, &val)))
		sysinfo_tdmr->pamt_4k_entry_size = val;
	if (!ret && !(ret = read_sys_metadata_field(0x9100000100000011, &val)))
		sysinfo_tdmr->pamt_2m_entry_size = val;
	if (!ret && !(ret = read_sys_metadata_field(0x9100000100000012, &val)))
		sysinfo_tdmr->pamt_1g_entry_size = val;
	if (!ret && !(ret = get_tdx_sys_info_dpamt_bits(sysinfo_tdmr, &val)))
		sysinfo_tdmr->pamt_page_bitmap_entry_bits = val;

	return ret;
}