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

From: [email-masked] (Marc Zyngier)
Date: Wed, 28 May 2014 15:14:05 +0100

On 28/05/14 14:45, Christoffer Dall wrote:
> On Wed, May 28, 2014 at 01:04:50PM +0100, Marc Zyngier wrote:
>> On 26/05/14 16:20, Christoffer Dall 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.
>>>
>>> Signed-off-by: Christoffer Dall <[email-masked]>
>>> ---
>>>  arch/arm/include/asm/kvm_mmu.h   |  12 ++++
>>>  arch/arm/kvm/mmu.c               | 126 ++++++++++++++++++++++-----------------
>>>  arch/arm64/include/asm/kvm_mmu.h |  15 +++++
>>>  3 files changed, 99 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..0572522 100644
>>> --- a/arch/arm/kvm/mmu.c
>>> +++ b/arch/arm/kvm/mmu.c
>>> @@ -46,6 +46,10 @@ static phys_addr_t hyp_idmap_vector;
>>>  
>>>  #define kvm_pmd_huge(_x)	(pmd_huge(_x) || pmd_trans_huge(_x))
>>>  
>>> +#ifndef __unused
>>> +#    define __unused			__attribute__((unused))
>>> +#endif
>>> +
>>
>> Do we actually need this?
>>
> 
> my GCC complains in clear_pgd_entry if pud's are not used.  Other
> suggestions on how to solve this are very welcome.

My point was not about the use of the "unused" attribute (I can see why
GCC screams when we don't have 4 levels of page tables), but I though
that we could use the "__maybe_unused" attribute (defined in compiler.h).

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