Subject: [PATCH 1/7] ARM: KVM: simplify HYP mapping population

From: [email-masked] (Marc Zyngier)
Date: Thu, 04 Apr 2013 13:35:17 +0100

On 04/04/13 00:13, Christoffer Dall wrote:
> On Tue, Apr 02, 2013 at 02:25:09PM +0100, Marc Zyngier wrote:
>> The way we populate HYP mappings is a bit convoluted, to say the least.
>> Passing a pointer around to keep track of the current PFN is quite
>> odd, and we end-up having two different PTE accessors for no good
>> reason.
>>
>> Simplify the whole thing by unifying the two PTE accessors, passing
>> a pgprot_t around, and moving the various validity checks to the
>> upper layers.
>>
>> Signed-off-by: Marc Zyngier <[email-masked]>
>> ---
>>  arch/arm/kvm/mmu.c | 100 ++++++++++++++++++++++-------------------------------
>>  1 file changed, 41 insertions(+), 59 deletions(-)
>>
>> diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
>> index 2f12e40..24811d1 100644
>> --- a/arch/arm/kvm/mmu.c
>> +++ b/arch/arm/kvm/mmu.c
>> @@ -125,54 +125,34 @@ void free_hyp_pmds(void)
>>  }
>>  
>>  static void create_hyp_pte_mappings(pmd_t *pmd, unsigned long start,
>> -				    unsigned long end)
>> +				    unsigned long end, unsigned long pfn,
>> +				    pgprot_t prot)
>>  {
>>  	pte_t *pte;
>>  	unsigned long addr;
>> -	struct page *page;
>>  
>> -	for (addr = start & PAGE_MASK; addr < end; addr += PAGE_SIZE) {
>> -		unsigned long hyp_addr = KERN_TO_HYP(addr);
>> -
>> -		pte = pte_offset_kernel(pmd, hyp_addr);
>> -		BUG_ON(!virt_addr_valid(addr));
>> -		page = virt_to_page(addr);
>> -		kvm_set_pte(pte, mk_pte(page, PAGE_HYP));
>> -	}
>> -}
>> -
>> -static void create_hyp_io_pte_mappings(pmd_t *pmd, unsigned long start,
>> -				       unsigned long end,
>> -				       unsigned long *pfn_base)
>> -{
>> -	pte_t *pte;
>> -	unsigned long addr;
>> -
>> -	for (addr = start & PAGE_MASK; addr < end; addr += PAGE_SIZE) {
>> -		unsigned long hyp_addr = KERN_TO_HYP(addr);
>> -
>> -		pte = pte_offset_kernel(pmd, hyp_addr);
>> -		BUG_ON(pfn_valid(*pfn_base));
>> -		kvm_set_pte(pte, pfn_pte(*pfn_base, PAGE_HYP_DEVICE));
>> -		(*pfn_base)++;
>> +	for (addr = start; addr < end; addr += PAGE_SIZE) {
>> +		pte = pte_offset_kernel(pmd, addr);
>> +		kvm_set_pte(pte, pfn_pte(pfn, prot));
>> +		pfn++;
>>  	}
>>  }
>>  
>>  static int create_hyp_pmd_mappings(pud_t *pud, unsigned long start,
>> -				   unsigned long end, unsigned long *pfn_base)
>> +				   unsigned long end, unsigned long pfn,
>> +				   pgprot_t prot)
>>  {
>>  	pmd_t *pmd;
>>  	pte_t *pte;
>>  	unsigned long addr, next;
>>  
>>  	for (addr = start; addr < end; addr = next) {
>> -		unsigned long hyp_addr = KERN_TO_HYP(addr);
>> -		pmd = pmd_offset(pud, hyp_addr);
>> +		pmd = pmd_offset(pud, addr);
>>  
>>  		BUG_ON(pmd_sect(*pmd));
>>  
>>  		if (pmd_none(*pmd)) {
>> -			pte = pte_alloc_one_kernel(NULL, hyp_addr);
>> +			pte = pte_alloc_one_kernel(NULL, addr);
>>  			if (!pte) {
>>  				kvm_err("Cannot allocate Hyp pte\n");
>>  				return -ENOMEM;
>> @@ -182,25 +162,17 @@ static int create_hyp_pmd_mappings(pud_t *pud, unsigned long start,
>>  
>>  		next = pmd_addr_end(addr, end);
>>  
>> -		/*
>> -		 * If pfn_base is NULL, we map kernel pages into HYP with the
>> -		 * virtual address. Otherwise, this is considered an I/O
>> -		 * mapping and we map the physical region starting at
>> -		 * *pfn_base to [start, end[.
>> -		 */
>> -		if (!pfn_base)
>> -			create_hyp_pte_mappings(pmd, addr, next);
>> -		else
>> -			create_hyp_io_pte_mappings(pmd, addr, next, pfn_base);
>> +		create_hyp_pte_mappings(pmd, addr, next, pfn, prot);
>> +		pfn += (next - addr) >> PAGE_SHIFT;
> 
> so this scheme always assumes a physically contiguous memory reason,
> and I wasn't sure if we ever wanted to support mapping vmalloc'ed
> regions into Hyp mode, which is why I wrote the code the way it was
> (which goes to your "for no good reason" comment above).

So let's look at what we're actually mapping:
- kernel code/kmalloc-ed data: this is always physically contiguous
- MMIO: While this is mapped in the vmalloc region, this is actually
physically contiguous.

> I'm fine with assuming that this only works for contiguous regions, but
> I think it deserves a line in the comments on the exported functions
> (the non-IO one anyway).

Sure, I'll add that.

>>  	}
>>  
>>  	return 0;
>>  }
>>  
>> -static int __create_hyp_mappings(void *from, void *to, unsigned long *pfn_base)
>> +static int __create_hyp_mappings(pgd_t *pgdp,
>> +				 unsigned long start, unsigned long end,
>> +				 unsigned long pfn, pgprot_t prot)
>>  {
>> -	unsigned long start = (unsigned long)from;
>> -	unsigned long end = (unsigned long)to;
>>  	pgd_t *pgd;
>>  	pud_t *pud;
>>  	pmd_t *pmd;
>> @@ -209,21 +181,14 @@ static int __create_hyp_mappings(void *from, void *to, unsigned long *pfn_base)
>>  
>>  	if (start >= end)
>>  		return -EINVAL;
>> -	/* Check for a valid kernel memory mapping */
>> -	if (!pfn_base && (!virt_addr_valid(from) || !virt_addr_valid(to - 1)))
>> -		return -EINVAL;
>> -	/* Check for a valid kernel IO mapping */
>> -	if (pfn_base && (!is_vmalloc_addr(from) || !is_vmalloc_addr(to - 1)))
>> -		return -EINVAL;
>>  
>>  	mutex_lock(&kvm_hyp_pgd_mutex);
>> -	for (addr = start; addr < end; addr = next) {
>> -		unsigned long hyp_addr = KERN_TO_HYP(addr);
>> -		pgd = hyp_pgd + pgd_index(hyp_addr);
>> -		pud = pud_offset(pgd, hyp_addr);
>> +	for (addr = start & PAGE_MASK; addr < end; addr = next) {
>> +		pgd = pgdp + pgd_index(addr);
>> +		pud = pud_offset(pgd, addr);
>>  
>>  		if (pud_none_or_clear_bad(pud)) {
>> -			pmd = pmd_alloc_one(NULL, hyp_addr);
>> +			pmd = pmd_alloc_one(NULL, addr);
>>  			if (!pmd) {
>>  				kvm_err("Cannot allocate Hyp pmd\n");
>>  				err = -ENOMEM;
>> @@ -233,9 +198,10 @@ static int __create_hyp_mappings(void *from, void *to, unsigned long *pfn_base)
>>  		}
>>  
>>  		next = pgd_addr_end(addr, end);
>> -		err = create_hyp_pmd_mappings(pud, addr, next, pfn_base);
>> +		err = create_hyp_pmd_mappings(pud, addr, next, pfn, prot);
>>  		if (err)
>>  			goto out;
>> +		pfn += (next - addr) >> PAGE_SHIFT;
> 
> nit: consider passing a pointer to pfn instead?  Not sure if it's nicer.

That's what we had before, and it wasn't that nice...

>>  	}
>>  out:
>>  	mutex_unlock(&kvm_hyp_pgd_mutex);
>> @@ -255,7 +221,16 @@ out:
>>   */
>>  int create_hyp_mappings(void *from, void *to)
>>  {
>> -	return __create_hyp_mappings(from, to, NULL);
>> +	unsigned long phys_addr = virt_to_phys(from);
>> +	unsigned long start = KERN_TO_HYP((unsigned long)from);
>> +	unsigned long end = KERN_TO_HYP((unsigned long)to);
>> +
>> +	/* Check for a valid kernel memory mapping */
>> +	if (!virt_addr_valid(from) || !virt_addr_valid(to - 1))
>> +		return -EINVAL;
>> +
>> +	return __create_hyp_mappings(hyp_pgd, start, end,
>> +				     __phys_to_pfn(phys_addr), PAGE_HYP);
>>  }
>>  
>>  /**
>> @@ -267,10 +242,17 @@ int create_hyp_mappings(void *from, void *to)
>>   * The resulting HYP VA is the same as the kernel VA, modulo
>>   * HYP_PAGE_OFFSET.
>>   */
>> -int create_hyp_io_mappings(void *from, void *to, phys_addr_t addr)
>> +int create_hyp_io_mappings(void *from, void *to, phys_addr_t phys_addr)
> 
> nit: change the parameter documentation name as well.

Sure.

> 
>>  {
>> -	unsigned long pfn = __phys_to_pfn(addr);
>> -	return __create_hyp_mappings(from, to, &pfn);
>> +	unsigned long start = KERN_TO_HYP((unsigned long)from);
>> +	unsigned long end = KERN_TO_HYP((unsigned long)to);
>> +
>> +	/* Check for a valid kernel IO mapping */
>> +	if (!is_vmalloc_addr(from) || !is_vmalloc_addr(to - 1))
>> +		return -EINVAL;
>> +
>> +	return __create_hyp_mappings(hyp_pgd, start, end,
>> +				     __phys_to_pfn(phys_addr), PAGE_HYP_DEVICE);
>>  }
>>  
>>  /**
>> -- 
>> 1.8.1.4
>>
> 
> If the contigous thing is not a concern, then I'm happy about the
> simplification.

Thanks,

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