Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
From:   Yajun Deng <yajun.deng@linux.dev>
To:     pbonzini@redhat.com, seanjc@google.com, vkuznets@redhat.com,
        wanpengli@tencent.com, jmattson@google.com, joro@8bytes.org,
        tglx@linutronix.de, mingo@redhat.com, bp@alien8.de,
        dave.hansen@linux.intel.com, hpa@zytor.com
Cc:     x86@kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
        Yajun Deng <yajun.deng@linux.dev>
Subject: [PATCH] KVM: x86: Move kzalloc out of atomic context on PREEMPT_RT
Date:   Thu, 19 May 2022 17:02:18 +0800
Message-Id: <20220519090218.2230653-1-yajun.deng@linux.dev>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

The memory allocator is fully preemptible and therefore cannot
be invoked from truly atomic contexts.

See Documentation/locking/locktypes.rst (line: 470)

Add raw_spin_unlock() before memory allocation and raw_spin_lock()
after it.

Signed-off-by: Yajun Deng <yajun.deng@linux.dev>
---
 arch/x86/kernel/kvm.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index d0bb2b3fb305..8f8ec9bbd847 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -205,7 +205,9 @@ void kvm_async_pf_task_wake(u32 token)
 		 * async PF was not yet handled.
 		 * Add dummy entry for the token.
 		 */
-		n = kzalloc(sizeof(*n), GFP_ATOMIC);
+		raw_spin_unlock(&b->lock);
+		n = kzalloc(sizeof(*n), GFP_KERNEL);
+		raw_spin_lock(&b->lock);
 		if (!n) {
 			/*
 			 * Allocation failed! Busy wait while other cpu
-- 
2.25.1