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Date: Tue, 01 Jun 2010 10:38:57 +0800 From: Xiao Guangrong <xiaoguangrong@...fujitsu.com> To: Avi Kivity <avi@...hat.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 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. Thanks, Xiao -- 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/
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