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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <0734a6cc7da3d210f403fdf3e0461ffba6b0aea0.camel@intel.com>
Date: Mon, 5 Jan 2026 22:06:31 +0000
From: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To: "yilun.xu@...ux.intel.com" <yilun.xu@...ux.intel.com>
CC: "kvm@...r.kernel.org" <kvm@...r.kernel.org>, "linux-coco@...ts.linux.dev"
	<linux-coco@...ts.linux.dev>, "Huang, Kai" <kai.huang@...el.com>, "Li,
 Xiaoyao" <xiaoyao.li@...el.com>, "Hansen, Dave" <dave.hansen@...el.com>,
	"Zhao, Yan Y" <yan.y.zhao@...el.com>, "Wu, Binbin" <binbin.wu@...el.com>,
	"kas@...nel.org" <kas@...nel.org>, "seanjc@...gle.com" <seanjc@...gle.com>,
	"mingo@...hat.com" <mingo@...hat.com>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "pbonzini@...hat.com" <pbonzini@...hat.com>,
	"Yamahata, Isaku" <isaku.yamahata@...el.com>,
	"kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
	"tglx@...utronix.de" <tglx@...utronix.de>, "Annapurve, Vishal"
	<vannapurve@...gle.com>, "Gao, Chao" <chao.gao@...el.com>, "bp@...en8.de"
	<bp@...en8.de>, "x86@...nel.org" <x86@...nel.org>
Subject: Re: [PATCH v4 04/16] x86/virt/tdx: Allocate page bitmap for Dynamic
 PAMT

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;
}