linux-kernel - Re: [PATCH v10 05/16] x86/virt/tdx: Add skeleton to enable TDX on demand

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Message-ID: <20230316003102.GB197448@ls.amr.corp.intel.com>
Date:   Wed, 15 Mar 2023 17:31:02 -0700
From:   Isaku Yamahata <isaku.yamahata@...il.com>
To:     Kai Huang <kai.huang@...el.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        linux-mm@...ck.org, dave.hansen@...el.com, peterz@...radead.org,
        tglx@...utronix.de, seanjc@...gle.com, pbonzini@...hat.com,
        dan.j.williams@...el.com, rafael.j.wysocki@...el.com,
        kirill.shutemov@...ux.intel.com, ying.huang@...el.com,
        reinette.chatre@...el.com, len.brown@...el.com,
        tony.luck@...el.com, ak@...ux.intel.com, isaku.yamahata@...el.com,
        chao.gao@...el.com, sathyanarayanan.kuppuswamy@...ux.intel.com,
        david@...hat.com, bagasdotme@...il.com, sagis@...gle.com,
        imammedo@...hat.com, isaku.yamahata@...il.com
Subject: Re: [PATCH v10 05/16] x86/virt/tdx: Add skeleton to enable TDX on
 demand

On Tue, Mar 07, 2023 at 03:13:50AM +1300,
Kai Huang <kai.huang@...el.com> wrote:

> +static int try_init_module_global(void)
> +{
> +	int ret;
> +
> +	/*
> +	 * The TDX module global initialization only needs to be done
> +	 * once on any cpu.
> +	 */
> +	spin_lock(&tdx_global_init_lock);


If I use tdx_cpu_enable() via kvm hardware_enable_all(), this function is called
in the context IPI callback and the lockdep complains.  Here is my patch to
address it

>From 0c4022ffe8cd68dfb455c418eb65538e4e100115 Mon Sep 17 00:00:00 2001
Message-Id: <0c4022ffe8cd68dfb455c418eb65538e4e100115.1678926123.git.isaku.yamahata@...el.com>
In-Reply-To: <d2aa2142665b8204b628232ab615c98090371c99.1678926122.git.isaku.yamahata@...el.com>
References: <d2aa2142665b8204b628232ab615c98090371c99.1678926122.git.isaku.yamahata@...el.com>
From: Isaku Yamahata <isaku.yamahata@...el.com>
Date: Wed, 15 Mar 2023 14:26:37 -0700
Subject: [PATCH] x86/virt/vmx/tdx: Use raw spin lock instead of spin lock

tdx_cpu_enable() can be called by IPI handler.  The lockdep complains about
spin lock as follows.  Use raw spin lock.

=============================
[ BUG: Invalid wait context ]
6.3.0-rc1-tdx-kvm-upstream+ #389 Not tainted
-----------------------------
swapper/154/0 is trying to lock:
ffffffffa7875e58 (tdx_global_init_lock){....}-{3:3}, at: tdx_cpu_enable+0x67/0x180
other info that might help us debug this:
context-{2:2}
no locks held by swapper/154/0.
stack backtrace:
Call Trace:
 <IRQ>
 dump_stack_lvl+0x64/0xb0
 dump_stack+0x10/0x20
 __lock_acquire+0x912/0xc30
 lock_acquire.part.0+0x99/0x220
 lock_acquire+0x60/0x170
 _raw_spin_lock_irqsave+0x43/0x70
 tdx_cpu_enable+0x67/0x180
 vt_hardware_enable+0x3b/0x60
 kvm_arch_hardware_enable+0xe7/0x2e0
 hardware_enable_nolock+0x33/0x80
 __flush_smp_call_function_queue+0xc4/0x590
 generic_smp_call_function_single_interrupt+0x1a/0xb0
 __sysvec_call_function+0x48/0x200
 sysvec_call_function+0xad/0xd0
 </IRQ>

Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
---
 arch/x86/virt/vmx/tdx/tdx.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
index 2ee37a5dedcf..e1c8ffad7406 100644
--- a/arch/x86/virt/vmx/tdx/tdx.c
+++ b/arch/x86/virt/vmx/tdx/tdx.c
@@ -41,7 +41,7 @@ static u32 tdx_guest_keyid_start __ro_after_init;
 static u32 tdx_nr_guest_keyids __ro_after_init;
 
 static unsigned int tdx_global_init_status;
-static DEFINE_SPINLOCK(tdx_global_init_lock);
+static DEFINE_RAW_SPINLOCK(tdx_global_init_lock);
 #define TDX_GLOBAL_INIT_DONE	_BITUL(0)
 #define TDX_GLOBAL_INIT_FAILED	_BITUL(1)
 
@@ -349,6 +349,7 @@ static void tdx_trace_seamcalls(u64 level)
 
 static int try_init_module_global(void)
 {
+	unsigned long flags;
 	u64 tsx_ctrl;
 	int ret;
 
@@ -356,7 +357,7 @@ static int try_init_module_global(void)
 	 * The TDX module global initialization only needs to be done
 	 * once on any cpu.
 	 */
-	spin_lock(&tdx_global_init_lock);
+	raw_spin_lock_irqsave(&tdx_global_init_lock, flags);
 
 	if (tdx_global_init_status & TDX_GLOBAL_INIT_DONE) {
 		ret = tdx_global_init_status & TDX_GLOBAL_INIT_FAILED ?
@@ -373,7 +374,7 @@ static int try_init_module_global(void)
 	if (ret)
 		tdx_global_init_status |= TDX_GLOBAL_INIT_FAILED;
 out:
-	spin_unlock(&tdx_global_init_lock);
+	raw_spin_unlock_irqrestore(&tdx_global_init_lock, flags);
 
 	if (ret) {
 		if (trace_boot_seamcalls)
-- 
2.25.1


-- 
Isaku Yamahata <isaku.yamahata@...il.com>