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From:   Tianjia Zhang <tianjia.zhang@linux.alibaba.com>
To:     Jarkko Sakkinen <jarkko@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Sean Christopherson <seanjc@google.com>,
        Shuah Khan <shuah@kernel.org>, x86@kernel.org,
        linux-sgx@vger.kernel.org, linux-kselftest@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        Jia Zhang <zhang.jia@linux.alibaba.com>
Cc:     Tianjia Zhang <tianjia.zhang@linux.alibaba.com>
Subject: [PATCH v3 2/5] x86/sgx: Optimize the locking range in sgx_sanitize_section()
Date:   Sun, 24 Jan 2021 14:29:04 +0800
Message-Id: <20210124062907.88229-3-tianjia.zhang@linux.alibaba.com>
In-Reply-To: <20210124062907.88229-1-tianjia.zhang@linux.alibaba.com>
References: <20210124062907.88229-1-tianjia.zhang@linux.alibaba.com>
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The spin lock of sgx_epc_section only locks the page_list. The
EREMOVE operation and init_laundry_list is not necessary in the
protection range of the spin lock. This patch reduces the lock
range of the spin lock in the function sgx_sanitize_section()
and only protects the operation of the page_list.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Tianjia Zhang <tianjia.zhang@linux.alibaba.com>
---
 arch/x86/kernel/cpu/sgx/main.c | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
index c519fc5f6948..4465912174fd 100644
--- a/arch/x86/kernel/cpu/sgx/main.c
+++ b/arch/x86/kernel/cpu/sgx/main.c
@@ -41,20 +41,17 @@ static void sgx_sanitize_section(struct sgx_epc_section *section)
 		if (kthread_should_stop())
 			return;
 
-		/* needed for access to ->page_list: */
-		spin_lock(&section->lock);
-
 		page = list_first_entry(&section->init_laundry_list,
 					struct sgx_epc_page, list);
 
 		ret = __eremove(sgx_get_epc_virt_addr(page));
-		if (!ret)
+		if (!ret) {
+			spin_lock(&section->lock);
 			list_move(&page->list, &section->page_list);
-		else
+			spin_unlock(&section->lock);
+		} else
 			list_move_tail(&page->list, &dirty);
 
-		spin_unlock(&section->lock);
-
 		cond_resched();
 	}
 
-- 
2.19.1.3.ge56e4f7