linux-kernel - Re: [PATCH v2] x86/sgx: Remove redundant if conditions in sgx_encl

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Message-ID: <95913686-be5f-85e5-0cc2-91b2a100e16e@linux.alibaba.com>
Date:   Sun, 24 Jan 2021 14:33:53 +0800
From:   Tianjia Zhang <tianjia.zhang@...ux.alibaba.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Jarkko Sakkinen <jarkko@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        linux-sgx@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jia Zhang <zhang.jia@...ux.alibaba.com>
Subject: Re: [PATCH v2] x86/sgx: Remove redundant if conditions in
 sgx_encl_create



On 1/21/21 1:47 AM, Sean Christopherson wrote:
> On Wed, Jan 20, 2021, Tianjia Zhang wrote:
>> In this scenario, there is no case where va_page is NULL, and
>> the error has been checked. The if condition statement here is
>> redundant, so remove the condition detection.
>>
>> Reported-by: Jia Zhang <zhang.jia@...ux.alibaba.com>
>> Suggested-by: Sean Christopherson <seanjc@...gle.com>
>> Signed-off-by: Tianjia Zhang <tianjia.zhang@...ux.alibaba.com>
>> ---
>>   arch/x86/kernel/cpu/sgx/ioctl.c | 9 ++++++---
>>   1 file changed, 6 insertions(+), 3 deletions(-)
>>
>> diff --git a/arch/x86/kernel/cpu/sgx/ioctl.c b/arch/x86/kernel/cpu/sgx/ioctl.c
>> index 1c6ecf9fbeff..efad2fb61c76 100644
>> --- a/arch/x86/kernel/cpu/sgx/ioctl.c
>> +++ b/arch/x86/kernel/cpu/sgx/ioctl.c
>> @@ -66,9 +66,12 @@ static int sgx_encl_create(struct sgx_encl *encl, struct sgx_secs *secs)
>>   	va_page = sgx_encl_grow(encl);
>>   	if (IS_ERR(va_page))
>>   		return PTR_ERR(va_page);
>> -	else if (va_page)
>> -		list_add(&va_page->list, &encl->va_pages);
>> -	/* else the tail page of the VA page list had free slots. */
>> +
>> +	if (WARN_ONCE(!va_page,
>> +		      "the tail page of the VA page list had free slots\n"))
> 
> IMO it's worth trimming down the message to keep this on a single line.  The
> newline isn't necessary, and this code expects a completely empty list, e.g. it
> can be reworded to something like:
> 
> 	if (WARN_ONCE(!va_page, "non-empty VA page list before ECREATE"))
> 

Thanks for your suggestion, I have resubmitted a set of patches.

Best regards,
Tianjia