Re: [PATCH v4 2/5] x86/sgx: Reduce the locking range in sgx_sanitize_section()

On 2/3/21 6:00 AM, Jarkko Sakkinen wrote:

On Mon, Feb 01, 2021 at 09:26:50PM +0800, Tianjia Zhang wrote:

...

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

I'm not confident that this change has any practical value.

/Jarkko

As a process executed during initialization, this optimization effect may not be obvious. If possible, this critical area can be moved outside to protect the entire while loop.

Best regards, Tianjia

...

---

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