On 08/04/16 14:15, Christoffer Dall wrote:
> On Mon, Apr 04, 2016 at 05:26:12PM +0100, Suzuki K Poulose wrote:
>> We have common routines to modify hyp and stage2 page tables
>> based on the 'kvm' parameter. For a smoother transition to
>> using separate routines for each, duplicate the routines
>> and modify the copy to work on hyp.
>>
>> Marks the forked routines with _hyp_ and gets rid of the
>> kvm parameter which is no longer needed and is NULL for hyp.
>> Also, gets rid of calls to kvm_tlb_flush_by_vmid_ipa() calls
>> from the hyp versions. Uses explicit host page table accessors
>> instead of the kvm_* page table helpers.
>>
>> Suggested-by: Christoffer Dall <christoffer.dall@xxxxxxxxxx>
>> Cc: Marc Zyngier <marc.zyngier@xxxxxxx>
>> Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
>> ---
>> arch/arm/kvm/mmu.c | 123 +++++++++++++++++++++++++++++++++++++++++++++++++---
>> 1 file changed, 118 insertions(+), 5 deletions(-)
>>
>> diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
>> index b46a337..2b491e5 100644
>> --- a/arch/arm/kvm/mmu.c
>> +++ b/arch/arm/kvm/mmu.c
>> @@ -388,6 +388,119 @@ static void stage2_flush_vm(struct kvm *kvm)
>> srcu_read_unlock(&kvm->srcu, idx);
>> }
>>
>> +static void clear_hyp_pgd_entry(pgd_t *pgd)
>> +{
>> + pud_t *pud_table __maybe_unused = pud_offset(pgd, 0UL);
>> + pgd_clear(pgd);
>> + pud_free(NULL, pud_table);
>> + put_page(virt_to_page(pgd));
>> +}
>> +
>> +static void clear_hyp_pud_entry(pud_t *pud)
>> +{
>> + pmd_t *pmd_table __maybe_unused = pmd_offset(pud, 0);
>> + VM_BUG_ON(pud_huge(*pud));
>> + pud_clear(pud);
>> + pmd_free(NULL, pmd_table);
>> + put_page(virt_to_page(pud));
>> +}
>> +
>> +static void clear_hyp_pmd_entry(pmd_t *pmd)
>> +{
>> + pte_t *pte_table = pte_offset_kernel(pmd, 0);
>> + VM_BUG_ON(pmd_thp_or_huge(*pmd));
>> + pmd_clear(pmd);
>> + pte_free_kernel(NULL, pte_table);
>> + put_page(virt_to_page(pmd));
>> +}
>> +
>> +static void unmap_hyp_ptes(pmd_t *pmd, phys_addr_t addr, phys_addr_t end)
>> +{
>> + pte_t *pte, *start_pte;
>> +
>> + start_pte = pte = pte_offset_kernel(pmd, addr);
>> + do {
>> + if (!pte_none(*pte)) {
>> + pte_t old_pte = *pte;
>> +
>> + kvm_set_pte(pte, __pte(0));
>> +
>> + /* XXX: Do we need to invalidate the cache for device mappings ? */
>
> no, we will not be swapping out any pages mapped in Hyp mode so you can
> get rid of both of the following two lines.
>
>> + if (!kvm_is_device_pfn(pte_pfn(old_pte)))
>> + kvm_flush_dcache_pte(old_pte);
>> +
>> + put_page(virt_to_page(pte));
>> + }
>> + } while (pte++, addr += PAGE_SIZE, addr != end);
>> +
>> + if (hyp_pte_table_empty(start_pte))
>> + clear_hyp_pmd_entry(pmd);
>> +}
>> +
>> +static void unmap_hyp_pmds(pud_t *pud, phys_addr_t addr, phys_addr_t end)
>> +{
>> + phys_addr_t next;
>> + pmd_t *pmd, *start_pmd;
>> +
>> + start_pmd = pmd = pmd_offset(pud, addr);
>> + do {
>> + next = pmd_addr_end(addr, end);
>> + if (!pmd_none(*pmd)) {
>> + if (pmd_thp_or_huge(*pmd)) {
>
> do we ever actually map anything with section mappings in the Hyp
> mappings?
No, this is purely a page mapping so far. On my system, the HYP text is
just over 4 pages big (4k pages), so the incentive is pretty low, unless
we can demonstrate some big gains due to the reduced TLB impact.
>> + pmd_t old_pmd = *pmd;
>> +
>> + pmd_clear(pmd);
>> + kvm_flush_dcache_pmd(old_pmd);
>> + put_page(virt_to_page(pmd));
>> + } else {
>> + unmap_hyp_ptes(pmd, addr, next);
>> + }
>> + }
>> + } while (pmd++, addr = next, addr != end);
>> +
>> + if (hyp_pmd_table_empty(start_pmd))
>> + clear_hyp_pud_entry(pud);
>> +}
>> +
>> +static void unmap_hyp_puds(pgd_t *pgd, phys_addr_t addr, phys_addr_t end)
>> +{
>> + phys_addr_t next;
>> + pud_t *pud, *start_pud;
>> +
>> + start_pud = pud = pud_offset(pgd, addr);
>> + do {
>> + next = pud_addr_end(addr, end);
>> + if (!pud_none(*pud)) {
>> + if (pud_huge(*pud)) {
>
> do we ever actually map anything with huge pud
> mappings for the Hyp space?
Same thing. Looks like there is some potential simplification here.
>
>> + pud_t old_pud = *pud;
>> +
>> + pud_clear(pud);
>> + kvm_flush_dcache_pud(old_pud);
>> + put_page(virt_to_page(pud));
>> + } else {
>> + unmap_hyp_pmds(pud, addr, next);
>> + }
>> + }
>> + } while (pud++, addr = next, addr != end);
>> +
>> + if (hyp_pud_table_empty(start_pud))
>> + clear_hyp_pgd_entry(pgd);
>> +}
>> +
>> +static void unmap_hyp_range(pgd_t *pgdp, phys_addr_t start, u64 size)
>> +{
>> + pgd_t *pgd;
>> + phys_addr_t addr = start, end = start + size;
>> + phys_addr_t next;
>> +
>> + pgd = pgdp + pgd_index(addr);
>> + do {
>> + next = pgd_addr_end(addr, end);
>> + if (!pgd_none(*pgd))
>> + unmap_hyp_puds(pgd, addr, next);
>> + } while (pgd++, addr = next, addr != end);
>
> shouldn't we flush the EL2 (hyp) TLB here, strictly speaking?
>
> Or do we rely on all mappings ever created/torn down here to always have
> the same VA/PA relationship? Since we didn't flush the EL2 TLB in the
> existing code, that indeed does seem to be the case.
Actually, we never unmap anything from HYP. Once a structure (kvm, vcpu)
is mapped there, it stays forever, whatever happens to the VM (that's
because we'd otherwise have to refcount the number of objects in a page,
and I'm lazy...).
> That, in turn, raises the question why we don't simply map all pages
> that could be referenced by a kmalloc() in Hyp mode during the init
> phase and be done with all this hyp mapping/unmapping stuff?
>
> In any case, that behavior doesn't have to change now, but if we don't
> add a TLB flush here, I'd like a comment to explain why that's not
> needed.
Hope you have your answer above... ;-)
Thanks,
M.
--
Jazz is not dead. It just smells funny...
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