linux-kernel - Re: [PATCH 1/1] x86/iommu: use bit structures for context

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <519EB798.2080904@hp.com>
Date:	Fri, 24 May 2013 08:43:04 +0800
From:	ZhenHua <zhen-hual@...com>
To:	Joe Perches <joe@...ches.com>
CC:	David Woodhouse <dwmw2@...radead.org>,
	iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] x86/iommu: use bit structures for context_entry

Use lo and hi for clear, may run faster than memset.

But it is not a big problem.  Never mind.

Thanks
ZhenHua

On 05/24/2013 08:36 AM, Joe Perches wrote:
> On Fri, 2013-05-24 at 08:22 +0800, Li, Zhen-Hua wrote:
>> There is a structure named context_entry used by intel iommu, and there
>> are some bit operations on it. Use bit structure may make these operations
>> easy.
> []
>> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
> []
>> @@ -221,55 +221,28 @@ get_context_addr_from_root(struct root_entry *root)
>>    * 8-23: domain id
>>    */
>>   struct context_entry {
>> -	u64 lo;
>> -	u64 hi;
>> +	union {
>> +		struct {
>> +			u64	present:1,
> why use struct and union at all?
>
> Why not just:
>
> struct context_entry {
> 	u64	present:1,
> 		fpd:1,
> 		translation_type:2,
> 		reserved_l:8,
> 		asr:52;
> 	u64	aw:3,
> 		avail:4,
> 		reserved_h1:1,
> 		did:16,
> 		reserved_h2:40;
> };
>
>> @@ -743,7 +716,8 @@ static void clear_context_table(struct intel_iommu *iommu, u8 bus, u8 devfn)
> []
>>   	if (context) {
>> -		context_clear_entry(&context[devfn]);
>> +		context[devfn].lo = 0;
>> +		context[devfn].hi = 0;
> 		memset(&context[devfn], 0, sizeof(...))
>
>

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/