On Tue, May 12, 2020 at 01:04:31PM +0100, James Morse wrote: > Hi Andrew, > > On 07/05/2020 16:13, Andrew Scull wrote: > >> @@ -176,7 +177,7 @@ static void clear_stage2_pud_entry(struct kvm_s2_mmu *mmu, pud_t *pud, phys_addr > >> pmd_t *pmd_table __maybe_unused = stage2_pmd_offset(kvm, pud, 0); > >> VM_BUG_ON(stage2_pud_huge(kvm, *pud)); > >> stage2_pud_clear(kvm, pud); > >> - kvm_tlb_flush_vmid_ipa(mmu, addr); > >> + kvm_tlb_flush_vmid_ipa(mmu, addr, S2_NO_LEVEL_HINT); > >> stage2_pmd_free(kvm, pmd_table); > >> put_page(virt_to_page(pud)); > >> } > >> @@ -186,7 +187,7 @@ static void clear_stage2_pmd_entry(struct kvm_s2_mmu *mmu, pmd_t *pmd, phys_addr > >> pte_t *pte_table = pte_offset_kernel(pmd, 0); > >> VM_BUG_ON(pmd_thp_or_huge(*pmd)); > >> pmd_clear(pmd); > >> - kvm_tlb_flush_vmid_ipa(mmu, addr); > >> + kvm_tlb_flush_vmid_ipa(mmu, addr, S2_NO_LEVEL_HINT); > >> free_page((unsigned long)pte_table); > >> put_page(virt_to_page(pmd)); > >> } > > > > Going by the names, is it possible to give a better level hint for these > > cases? > > There is no leaf entry being invalidated here. After clearing the range, we found we'd > emptied (and invalidated) a whole page of mappings: > | if (stage2_pmd_table_empty(kvm, start_pmd)) > | clear_stage2_pud_entry(mmu, pud, start_addr); > > Now we want to remove the link to the empty page so we can free it. We are changing the > structure of the tables, not what gets mapped. > > I think this is why we need the un-hinted behaviour, to invalidate "any level of the > translation table walk required to translate the specified IPA". Otherwise the hardware > can look for a leaf at the indicated level, find none, and do nothing. > > > This is sufficiently horrible, its possible I've got it completely wrong! (does it make > sense?) Ok. `addr` is an IPA, that IPA is now omitted from the map so doesn't appear in any entry of the table, least of all a leaf entry. That makes sense. Is there a convention to distinguish IPA and PA similar to the distinction for VA or does kvmarm just use phys_addr_t all round? It seems like the TTL patches are failry self contained if it would be easier to serparate them out from these larger series?
