[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH 5/5] x86_64/mm: map and unmap page tables in destroy_m2p_mapping
On Wed, 2020-04-01 at 14:40 +0200, Jan Beulich wrote: > On 23.03.2020 10:41, Hongyan Xia wrote: > > @@ -297,26 +298,33 @@ static void destroy_m2p_mapping(struct > > mem_hotadd_info *info) > > continue; > > } > > > > - l2_ro_mpt = l3e_to_l2e(l3_ro_mpt[l3_table_offset(va)]); > > + l2_ro_mpt = > > map_l2t_from_l3e(l3_ro_mpt[l3_table_offset(va)]); > > if (!(l2e_get_flags(l2_ro_mpt[l2_table_offset(va)]) & > > _PAGE_PRESENT)) > > { > > i = ( i & ~((1UL << (L2_PAGETABLE_SHIFT - 3)) - 1)) + > > (1UL << (L2_PAGETABLE_SHIFT - 3)) ; > > + UNMAP_DOMAIN_PAGE(l2_ro_mpt); > > continue; > > } > > > > pt_pfn = l2e_get_pfn(l2_ro_mpt[l2_table_offset(va)]); > > if ( hotadd_mem_valid(pt_pfn, info) ) > > { > > + l2_pgentry_t *l2t; > > + > > destroy_xen_mappings(rwva, rwva + (1UL << > > L2_PAGETABLE_SHIFT)); > > > > - l2_ro_mpt = > > l3e_to_l2e(l3_ro_mpt[l3_table_offset(va)]); > > - l2e_write(&l2_ro_mpt[l2_table_offset(va)], > > l2e_empty()); > > + l2t = > > map_l2t_from_l3e(l3_ro_mpt[l3_table_offset(va)]); > > Why a 2nd mapping of the same L3 entry that you've already mapped > into l2_ro_mpt? > > + l2e_write(&l2t[l2_table_offset(va)], l2e_empty()); > > + UNMAP_DOMAIN_PAGE(l2t); > > If this then weren't to go away, it should again be the lowercase > variant imo, as the variable's scope ends here. Hmm, I don't see a reason why l2_ro_mpt needs to be mapped again either (and don't see why it was re-derived in the original code), so yes, I think the map and unmap can just be dropped. Will revise. Hongyan
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