Subject: [PATCH v2] arm/arm64: KVM: Fix and refactor unmap_range

From: [email-masked] (Marc Zyngier)
Date: Wed, 04 Jun 2014 14:37:42 +0100

On 04/06/14 14:30, Christoffer Dall wrote:
> On Tue, Jun 03, 2014 at 02:52:58PM +0100, Steve Capper wrote:
>> Hi Christoffer,
>> I have some comments below:
>>
>> On 28 May 2014 15:22, Christoffer Dall <[email-masked]> wrote:
>>> unmap_range() was utterly broken, to quote Marc, and broke in all sorts
>>> of situations.  It was also quite complicated to follow and didn't
>>> follow the usual scheme of having a separate iterating function for each
>>> level of page tables.
>>>
>>> Address this by refactoring the code and introduce a pgd_clear()
>>> function.
>>>
>>> Acked-by: Marc Zyngier <[email-masked]>
>>> Signed-off-by: Christoffer Dall <[email-masked]>
>>> ---
>>> Changes since v2:
>>>  - Don't define custom __unused but reuse __maybe_unused
>>>
>>>  arch/arm/include/asm/kvm_mmu.h   |  12 ++++
>>>  arch/arm/kvm/mmu.c               | 122 ++++++++++++++++++++++-----------------
>>>  arch/arm64/include/asm/kvm_mmu.h |  15 +++++
>>>  3 files changed, 95 insertions(+), 54 deletions(-)
>>>
>>> diff --git a/arch/arm/include/asm/kvm_mmu.h b/arch/arm/include/asm/kvm_mmu.h
>>> index 5c7aa3c..5cc0b0f 100644
>>> --- a/arch/arm/include/asm/kvm_mmu.h
>>> +++ b/arch/arm/include/asm/kvm_mmu.h
>>> @@ -127,6 +127,18 @@ static inline void kvm_set_s2pmd_writable(pmd_t *pmd)
>>>         (__boundary - 1 < (end) - 1)? __boundary: (end);                \
>>>  })
>>>
>>> +static inline bool kvm_page_empty(void *ptr)
>>> +{
>>> +       struct page *ptr_page = virt_to_page(ptr);
>>> +       return page_count(ptr_page) == 1;
>>> +}
>>> +
>>> +
>>> +#define kvm_pte_table_empty(ptep) kvm_page_empty(ptep)
>>> +#define kvm_pmd_table_empty(pmdp) kvm_page_empty(pmdp)
>>> +#define kvm_pud_table_empty(pudp) (0)
>>> +
>>> +
>>>  struct kvm;
>>>
>>>  #define kvm_flush_dcache_to_poc(a,l)   __cpuc_flush_dcache_area((a), (l))
>>> diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
>>> index 16f8049..6ee6e06 100644
>>> --- a/arch/arm/kvm/mmu.c
>>> +++ b/arch/arm/kvm/mmu.c
>>> @@ -90,10 +90,13 @@ static void *mmu_memory_cache_alloc(struct kvm_mmu_memory_cache *mc)
>>>         return p;
>>>  }
>>>
>>> -static bool page_empty(void *ptr)
>>> +static void clear_pgd_entry(struct kvm *kvm, pgd_t *pgd, phys_addr_t addr)
>>>  {
>>> -       struct page *ptr_page = virt_to_page(ptr);
>>> -       return page_count(ptr_page) == 1;
>>> +       pud_t *pud_table __maybe_unused = pud_offset(pgd, 0);
>>> +       pgd_clear(pgd);
>>> +       kvm_tlb_flush_vmid_ipa(kvm, addr);
>>> +       pud_free(NULL, pud_table);
>>> +       put_page(virt_to_page(pgd));
>>>  }
>>>
>>>  static void clear_pud_entry(struct kvm *kvm, pud_t *pud, phys_addr_t addr)
>>> @@ -124,70 +127,81 @@ static void clear_pmd_entry(struct kvm *kvm, pmd_t *pmd, phys_addr_t addr)
>>>         put_page(virt_to_page(pmd));
>>>  }
>>>
>>> -static void clear_pte_entry(struct kvm *kvm, pte_t *pte, phys_addr_t addr)
>>> +static void unmap_ptes(struct kvm *kvm, pmd_t *pmd,
>>> +                      unsigned long long addr, unsigned long long end)
>>
>> We have a lot of unsigned long longs in this patch, should they not be
>> phys_addr_t instead?
>>
> 
> I guess they should, I *think* the confusion came from the fact that
> unmap_range is also called on the hyp page table manipulation code,
> which works on VAs and not PAs, and we wanted to avoid the confusion.
> But I can't be sure.
> 
> That being said, I'm thinking that once we fix the whoel
> SL0/TTBR0_X/T0SZ dynamic mess, then this function may no longer work for
> both hyp page tables and Stage-2 page tables and then even this pseudo
> relevant argument goes away.
> 
> I would like to see if Marc remembers something here, but otherwise we
> could change all the unsigned long long's to phys_addr_t's.

I don't think that'd be a problem, as long as we have a nice comment
about that.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...