From: Jarkko Sakkinen <jarkko@kernel.org>
To: Tianjia Zhang <tianjia.zhang@linux.alibaba.com>
Cc: 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>
Subject: Re: [PATCH v3 3/5] x86/sgx: Optimize the free_cnt count in sgx_epc_section
Date: Wed, 27 Jan 2021 19:40:49 +0200 [thread overview]
Message-ID: <YBGlodsOaX4cWAtl@kernel.org> (raw)
In-Reply-To: <20210124062907.88229-4-tianjia.zhang@linux.alibaba.com>
I could bet some money that this does not bring any significant
performance gain.
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.
> } else
> list_move_tail(&page->list, &dirty);
> @@ -643,7 +644,6 @@ static bool __init sgx_setup_epc_section(u64 phys_addr, u64 size,
> list_add_tail(§ion->pages[i].list, §ion->init_laundry_list);
> }
>
> - section->free_cnt = nr_pages;
> return true;
> }
>
> --
> 2.19.1.3.ge56e4f7
>
>
/Jarkko
next prev parent reply other threads:[~2021-01-27 17:42 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-24 6:29 [PATCH v3 0/5] Some optimizations related to sgx Tianjia Zhang
2021-01-24 6:29 ` [PATCH v3 1/5] selftests/x86: Simplify the code to get vdso base address in sgx Tianjia Zhang
2021-01-24 6:29 ` [PATCH v3 2/5] x86/sgx: Optimize the locking range in sgx_sanitize_section() Tianjia Zhang
2021-01-30 13:24 ` Jarkko Sakkinen
2021-01-24 6:29 ` [PATCH v3 3/5] x86/sgx: Optimize the free_cnt count in sgx_epc_section Tianjia Zhang
2021-01-27 17:40 ` Jarkko Sakkinen [this message]
2021-02-11 6:04 ` Tianjia Zhang
2021-02-12 12:19 ` Jarkko Sakkinen
2021-02-16 3:30 ` Tianjia Zhang
2021-01-24 6:29 ` [PATCH v3 4/5] x86/sgx: Allows ioctl PROVISION to execute before CREATE Tianjia Zhang
2021-01-30 13:26 ` Jarkko Sakkinen
2021-02-01 12:55 ` Tianjia Zhang
2021-01-24 6:29 ` [PATCH v3 5/5] x86/sgx: Remove redundant if conditions in sgx_encl_create Tianjia Zhang
2021-01-24 8:20 ` Greg KH
2021-01-25 18:46 ` Sean Christopherson
2021-01-30 14:33 ` Jarkko Sakkinen
2021-02-01 12:37 ` Tianjia Zhang
2021-01-25 17:22 ` [PATCH v3 0/5] Some optimizations related to sgx Jarkko Sakkinen
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