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

From: [email-masked] (Christoffer Dall)
Date: Wed, 3 Apr 2013 16:13:44 -0700

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).

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).

>  	}
>  
>  	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.

>  	}
>  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.

>  {
> -	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.

-Christoffer