linux-kernel - Re: [PATCH v7 9/9] sparc64: Add support for ADI (Application Data Integrity)

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Date:   Wed, 16 Aug 2017 08:44:58 -0600
From:   Khalid Aziz <khalid.aziz@...cle.com>
To:     David Miller <davem@...emloft.net>
Cc:     dave.hansen@...ux.intel.com, corbet@....net, bob.picco@...cle.com,
        steven.sistare@...cle.com, pasha.tatashin@...cle.com,
        mike.kravetz@...cle.com, mingo@...nel.org,
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        linux-mm@...ck.org, khalid@...ehiking.org
Subject: Re: [PATCH v7 9/9] sparc64: Add support for ADI (Application Data
 Integrity)

On 08/15/2017 10:58 PM, David Miller wrote:
> From: Khalid Aziz <khalid.aziz@...cle.com>
> Date: Wed,  9 Aug 2017 15:26:02 -0600
> 
>> +void adi_restore_tags(struct mm_struct *mm, struct vm_area_struct *vma,
>> +		      unsigned long addr, pte_t pte)
>> +{
>   ...
>> +	tag = tag_start(addr, tag_desc);
>> +	paddr = pte_val(pte) & _PAGE_PADDR_4V;
>> +	for (tmp = paddr; tmp < (paddr+PAGE_SIZE); tmp += adi_blksize()) {
>> +		version1 = (*tag) >> 4;
>> +		version2 = (*tag) & 0x0f;
>> +		*tag++ = 0;
>> +		asm volatile("stxa %0, [%1] %2\n\t"
>> +			:
>> +			: "r" (version1), "r" (tmp),
>> +			  "i" (ASI_MCD_REAL));
>> +		tmp += adi_blksize();
>> +		asm volatile("stxa %0, [%1] %2\n\t"
>> +			:
>> +			: "r" (version2), "r" (tmp),
>> +			  "i" (ASI_MCD_REAL));
>> +	}
>> +	asm volatile("membar #Sync\n\t");
> 
> You do a membar here.
> 
>> +		for (i = pfrom; i < (pfrom + PAGE_SIZE); i += adi_blksize()) {
>> +			asm volatile("ldxa [%1] %2, %0\n\t"
>> +					: "=r" (adi_tag)
>> +					:  "r" (i), "i" (ASI_MCD_REAL));
>> +			asm volatile("stxa %0, [%1] %2\n\t"
>> +					:
>> +					: "r" (adi_tag), "r" (pto),
>> +					  "i" (ASI_MCD_REAL));
> 
> But not here.
> 
> Is this OK?  I suspect you need to add a membar this this second piece
> of MCD tag storing code.

Hi Dave,

You are right. This tag storing code needs membar as well. I will add that.

Thanks,
Khalid