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Message-ID: <4C04C028.8050506@redhat.com>
Date: Tue, 01 Jun 2010 11:09:12 +0300
From: Avi Kivity <avi@...hat.com>
To: Xiao Guangrong <xiaoguangrong@...fujitsu.com>
CC: Marcelo Tosatti <mtosatti@...hat.com>,
LKML <linux-kernel@...r.kernel.org>,
KVM list <kvm@...r.kernel.org>
Subject: Re: [PATCH 1/5] KVM: MMU: introduce some macros to cleanup hlist
traverseing
On 06/01/2010 05:38 AM, Xiao Guangrong wrote:
>
> Avi Kivity wrote:
>
>> On 05/31/2010 05:00 AM, Xiao Guangrong wrote:
>>
>>>
>>>>
>>>>
>>>>> +
>>>>> +#define for_each_gfn_indirect_sp(kvm, sp, gfn, pos, n) \
>>>>> + hlist_for_each_entry_safe(sp, pos, n, \
>>>>> +&kvm->arch.mmu_page_hash[kvm_page_table_hashfn(gfn)], hash_link)\
>>>>> + if (sp->gfn == gfn&& !sp->role.direct)
>>>>> +
>>>>> +#define for_each_gfn_indirect_valid_sp(kvm, sp, gfn, pos, n) \
>>>>> + hlist_for_each_entry_safe(sp, pos, n, \
>>>>> +&kvm->arch.mmu_page_hash[kvm_page_table_hashfn(gfn)], hash_link)\
>>>>> + if (sp->gfn == gfn&& !sp->role.direct&& \
>>>>> + !sp->role.invalid)
>>>>>
>>>>>
>>>>>
>>>> Shouldn't we always skip invalid gfns?
>>>>
>>>>
>>> Actually, in kvm_mmu_unprotect_page() function, it need find out
>>> invalid shadow pages:
>>>
>>> | hlist_for_each_entry_safe(sp, node, n, bucket, hash_link)
>>> | if (sp->gfn == gfn&& !sp->role.direct) {
>>> | pgprintk("%s: gfn %lx role %x\n", __func__, gfn,
>>> | sp->role.word);
>>> | r = 1;
>>> | if (kvm_mmu_zap_page(kvm, sp))
>>> | goto restart;
>>> | }
>>>
>>> I'm not sure whether we can skip invalid sp here, since it can change
>>> this
>>> function's return value. :-(
>>>
>>>
>> Hm. Invalid pages don't need to be write protected. So I think you can
>> patch unprotect_page() to ignore invalid pages, and then you can convert
>> it to the new macros which ignore invalid pages as well.
>>
>> The invariant is: if an sp exists with !role.invalid and !unsync, then
>> the page must be write protected.
>>
> OK, will fix it in the next version.
>
>
>>
>>
>>>> What about providing both gfn and role to the macro?
>>>>
>>>>
>>>>
>>> In current code, no code simply use role and gfn to find sp,
>>> in kvm_mmu_get_page(), we need do other work for
>>> 'sp->gfn == gfn&& sp->role != role' sp, and other functions only need
>>> compare
>>> some members in role, but not all members.
>>>
>>>
>> How about just gfn? I think everything compares against that!
>>
>>
> In this patch, it already introduced a macro to only compares 'gfn', that is:
>
> +#define for_each_gfn_sp(kvm, sp, gfn, pos, n) \
> + hlist_for_each_entry_safe(sp, pos, n, \
> + &kvm->arch.mmu_page_hash[kvm_page_table_hashfn(gfn)], hash_link)\
> + if (sp->gfn == gfn)
>
> Sorry if i misunderstand your meaning.
>
No, I got confused.
--
error compiling committee.c: too many arguments to function
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