On 03/12/2019 04:07 PM, Suzuki K Poulose wrote:
> Hi Anshuman,
>
> On 12/03/2019 02:19, Anshuman Khandual wrote:
>> ARM64 standard pgtable functions are going to use pgtable_page_[ctor|dtor]
>> or pgtable_pmd_page_[ctor|dtor] constructs. At present KVM guest stage-2
>> PUD|PMD|PTE level page tabe pages are allocated with __get_free_page()
>> via mmu_memory_cache_alloc() but released with standard pud|pmd_free() or
>> pte_free_kernel(). These will fail once they start calling into pgtable_
>> [pmd]_page_dtor() for pages which never originally went through respective
>> constructor functions. Hence convert all stage-2 page table page release
>> functions to call buddy directly while freeing pages.
>>
>> Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
>> ---
>> arch/arm/include/asm/stage2_pgtable.h | 4 ++--
>> arch/arm64/include/asm/stage2_pgtable.h | 4 ++--
>> virt/kvm/arm/mmu.c | 2 +-
>> 3 files changed, 5 insertions(+), 5 deletions(-)
>>
>> diff --git a/arch/arm/include/asm/stage2_pgtable.h b/arch/arm/include/asm/stage2_pgtable.h
>> index de2089501b8b..417a3be00718 100644
>> --- a/arch/arm/include/asm/stage2_pgtable.h
>> +++ b/arch/arm/include/asm/stage2_pgtable.h
>> @@ -32,14 +32,14 @@
>> #define stage2_pgd_present(kvm, pgd) pgd_present(pgd)
>> #define stage2_pgd_populate(kvm, pgd, pud) pgd_populate(NULL, pgd, pud)
>> #define stage2_pud_offset(kvm, pgd, address) pud_offset(pgd, address)
>> -#define stage2_pud_free(kvm, pud) pud_free(NULL, pud)
>> +#define stage2_pud_free(kvm, pud) free_page((unsigned long)pud)
>
> That must be a NOP, as we don't have pud on arm32 (we have 3 level table).
> The pud_* helpers here all fallback to the generic no-pud helpers.
Which is the following here for pud_free()
#define pud_free(mm, x) do { } while (0)
On arm64 its protected by kvm_stage2_has_pud() helper before calling into pud_free().
In this case even though applicable pud_free() is NOP, it is still misleading. If we
are sure about page table level will always remain three it can directly have a NOP
(do/while) in there.
