linux-kernel - Re: [RFC PATCH 04/20] x86/virt/tdx: Introduce a "tdx" subsystem and "tsm" device

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Message-ID: <aEFWgV0a2kLI62Bf@intel.com>
Date: Thu, 5 Jun 2025 16:34:09 +0800
From: Chao Gao <chao.gao@...el.com>
To: "Huang, Kai" <kai.huang@...el.com>
CC: "kvm@...r.kernel.org" <kvm@...r.kernel.org>, "linux-coco@...ts.linux.dev"
	<linux-coco@...ts.linux.dev>, "x86@...nel.org" <x86@...nel.org>, "Shutemov,
 Kirill" <kirill.shutemov@...el.com>, "Dong, Eddie" <eddie.dong@...el.com>,
	"Hansen, Dave" <dave.hansen@...el.com>, "dave.hansen@...ux.intel.com"
	<dave.hansen@...ux.intel.com>, "Reshetova, Elena"
	<elena.reshetova@...el.com>, "kirill.shutemov@...ux.intel.com"
	<kirill.shutemov@...ux.intel.com>, "seanjc@...gle.com" <seanjc@...gle.com>,
	"mingo@...hat.com" <mingo@...hat.com>, "pbonzini@...hat.com"
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 Isaku" <isaku.yamahata@...el.com>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "hpa@...or.com" <hpa@...or.com>, "Chen,
 Farrah" <farrah.chen@...el.com>, "Edgecombe, Rick P"
	<rick.p.edgecombe@...el.com>, "bp@...en8.de" <bp@...en8.de>, "Williams, Dan
 J" <dan.j.williams@...el.com>
Subject: Re: [RFC PATCH 04/20] x86/virt/tdx: Introduce a "tdx" subsystem and
 "tsm" device

On Tue, Jun 03, 2025 at 07:44:08AM +0800, Huang, Kai wrote:
>
>>  static int init_tdx_module(void)
>>  {
>>  	int ret;
>> @@ -1136,6 +1209,8 @@ static int init_tdx_module(void)
>>  
>>  	pr_info("%lu KB allocated for PAMT\n", tdmrs_count_pamt_kb(&tdx_tdmr_list));
>>  
>> +	tdx_subsys_init();
>> +
>>  out_put_tdxmem:
>>  	/*
>>  	 * @tdx_memlist is written here and read at memory hotplug time.
>
>The error handling of init_module_module() is already very heavy.  Although
>tdx_subsys_init() doesn't return any error, I would prefer to putting
>tdx_subsys_init() to __tdx_enable() (the caller of init_tdx_module()) so that
>init_tdx_module() can just focus on initializing the TDX module.

Sounds good. Will do.

btw, I think we can use guard() to simplify the error-handling a bit, e.g.,

diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
index a755cdef69d2..0b93064b9e0f 100644
--- a/arch/x86/virt/vmx/tdx/tdx.c
+++ b/arch/x86/virt/vmx/tdx/tdx.c
@@ -1218,11 +1218,11 @@ static int init_tdx_module(void)
	 * holding mem_hotplug_lock read-lock as the memory hotplug code
	 * path reads the @tdx_memlist to reject any new memory.
	 */
-	get_online_mems();
+	guard(online_mems)();
 
	ret = build_tdx_memlist(&tdx_memlist);
	if (ret)
-		goto out_put_tdxmem;
+		return ret;
 
	/* Allocate enough space for constructing TDMRs */
	ret = alloc_tdmr_list(&tdx_tdmr_list, &tdx_sysinfo.tdmr);
@@ -1253,13 +1253,7 @@ static int init_tdx_module(void)
 
	tdx_subsys_init();
 
-out_put_tdxmem:
-	/*
-	 * @tdx_memlist is written here and read at memory hotplug time.
-	 * Lock out memory hotplug code while building it.
-	 */
-	put_online_mems();
-	return ret;
+	return 0;
 
 err_reset_pamts:
	/*
@@ -1283,7 +1277,7 @@ static int init_tdx_module(void)
	free_tdmr_list(&tdx_tdmr_list);
 err_free_tdxmem:
	free_tdx_memlist(&tdx_memlist);
-	goto out_put_tdxmem;
+	return ret;
 }
 
 static int __tdx_enable(void)
diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index eaac5ae8c05c..a0c0535a9122 100644
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h
@@ -2,6 +2,7 @@
 #ifndef __LINUX_MEMORY_HOTPLUG_H
 #define __LINUX_MEMORY_HOTPLUG_H
 
+#include <linux/cleanup.h>
 #include <linux/mmzone.h>
 #include <linux/spinlock.h>
 #include <linux/notifier.h>
@@ -172,6 +173,7 @@ int add_pages(int nid, unsigned long start_pfn, unsigned long nr_pages,
 
 void get_online_mems(void);
 void put_online_mems(void);
+DEFINE_LOCK_GUARD_0(online_mems, get_online_mems(), put_online_mems())
 
 void mem_hotplug_begin(void);
 void mem_hotplug_done(void);