Hi Andrew,

On 07/05/2020 16:13, Andrew Scull wrote:

quoted

@@ -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?)


Thanks,

James

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