2021-01-24 06:32:52

by Tianjia Zhang

Subject: [PATCH v3 2/5] x86/sgx: Optimize the locking range in sgx_sanitize_section()

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 <[email protected]>
Signed-off-by: Tianjia Zhang <[email protected]>
---
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

2021-01-30 13:28:10

by Jarkko Sakkinen

Subject: Re: [PATCH v3 2/5] x86/sgx: Optimize the locking range in sgx_sanitize_section()

On Sun, Jan 24, 2021 at 02:29:04PM +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 <[email protected]>
> Signed-off-by: Tianjia Zhang <[email protected]>

I prefer to use the word "optimize" only if there is supporting
data to show that the code change has significant value.

/Jarkko