Messages in this thread | | | Subject | Re: [PATCH v3 3/5] x86/sgx: Optimize the free_cnt count in sgx_epc_section | From | Tianjia Zhang <> | Date | Thu, 11 Feb 2021 14:04:12 +0800 |
| |
Hi,
Sorry for the late reply.
On 1/28/21 1:40 AM, Jarkko Sakkinen wrote: > I could bet some money that this does not bring any significant > performance gain. >
Yes, this does not bring performance gains. This is not a change for performance, mainly to make the value of free_cnt look more accurate.
> On Sun, Jan 24, 2021 at 02:29:05PM +0800, Tianjia Zhang wrote: >> `section->free_cnt` represents the free page in sgx_epc_section, >> which is assigned once after initialization. In fact, just after the >> initialization is completed, the pages are in the `init_laundry_list` >> list and cannot be allocated. This needs to be recovered by EREMOVE >> of function sgx_sanitize_section() before it can be used as a page >> that can be allocated. The sgx_sanitize_section() will be called in >> the kernel thread ksgxd. >> >> This patch moves the initialization of `section->free_cnt` from the >> initialization function `sgx_setup_epc_section()` to the function >> `sgx_sanitize_section()`, and then accumulates the count after the > > Use single quotes instead of hyphens. > >> successful execution of EREMOVE. This seems to be more reasonable, >> free_cnt will also truly reflect the allocatable free pages in EPC. >> >> Sined-off-by: Tianjia Zhang <tianjia.zhang@linux.alibaba.com> >> Reviewed-by: Sean Christopherson <seanjc@google.com> >> --- >> arch/x86/kernel/cpu/sgx/main.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c >> index 4465912174fd..e455ec7b3449 100644 >> --- a/arch/x86/kernel/cpu/sgx/main.c >> +++ b/arch/x86/kernel/cpu/sgx/main.c >> @@ -48,6 +48,7 @@ static void sgx_sanitize_section(struct sgx_epc_section *section) >> if (!ret) { >> spin_lock(§ion->lock); >> list_move(&page->list, §ion->page_list); >> + section->free_cnt++; >> spin_unlock(§ion->lock); > > Someone can try to allocate a page while sanitize process is in progress. > > I think it is better to keep critical sections in the form that when you > leave from one, the global state is legit. >
Do you mean to move the critical section to protect the entire while loop? Of course, this is also possible, sanitize is a process only needed for initialization, and the possibility of conflict is very small.
Best regards, Tianjia
| |