linux-kernel - Re: [PATCH v2 12/13] KVM: x86: add SMM to the MMU role, support SMRAM address space

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

Message-ID: <558250D4.3050505@linux.intel.com>
Date:	Thu, 18 Jun 2015 13:02:12 +0800
From:	Xiao Guangrong <guangrong.xiao@...ux.intel.com>
To:	Paolo Bonzini <pbonzini@...hat.com>, linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org
CC:	rkrcmar@...hat.com, bdas@...hat.com
Subject: Re: [PATCH v2 12/13] KVM: x86: add SMM to the MMU role, support SMRAM
 address space



On 06/17/2015 04:18 PM, Paolo Bonzini wrote:
>
>
> On 09/06/2015 06:01, Xiao Guangrong wrote:
>>
>>
>> On 05/28/2015 01:05 AM, Paolo Bonzini wrote:
>>> This is now very simple to do.  The only interesting part is a simple
>>> trick to find the right memslot in gfn_to_rmap, retrieving the address
>>> space from the spte role word.  The same trick is used in the auditing
>>> code.
>>>
>>> The comment on top of union kvm_mmu_page_role has been stale forever,
>>
>> Fortunately, we have documented these fields in mmu.txt, please do it for
>> 'smm' as well. :)
>
> Right, done.
>
>>> +        /*
>>> +         * This is left at the top of the word so that
>>> +         * kvm_memslots_for_spte_role can extract it with a
>>> +         * simple shift.  While there is room, give it a whole
>>> +         * byte so it is also faster to load it from memory.
>>> +         */
>>> +        unsigned smm:8;
>>
>> I suspect if we really need this trick, smm is not the hottest filed in
>> this struct anyway.
>
> Note that after these patches it is used by gfn_to_rmap, and hence for
> example rmap_add.

However, role->level is more hotter than role->smm so that it's also a good
candidate for this kind of trick.

And this is only 32 bits which can be operated in a CPU register by a single
memory load, that is why i was worried if it is really needed.


--
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/