Messages in this thread |  | | | Date | Mon, 31 May 2010 14:14:35 +0300 | | From | Avi Kivity <> | | Subject | Re: [PATCH 1/5] KVM: MMU: introduce some macros to cleanup hlist traverseing |
| |
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.
>> 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!
-- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain.
|  |