Re: [PATCH v2 12/17] kvm-arm: Add explicit hyp page table modifiers

[Christoffer Dall]

On Thu, Apr 14, 2016 at 02:21:00PM +0100, Suzuki K Poulose wrote:
> We have common routines to modify hyp and stage2 page tables
> based on the 'kvm' parameter. For a smoother transition to
> using separate routines for each, duplicate the routines
> and modify the copy to work on hyp.
> 
> Marks the forked routines with _hyp_ and gets rid of the
> kvm parameter which is no longer needed and is NULL for hyp.
> Also, gets rid of calls to kvm_tlb_flush_by_vmid_ipa() calls
> from the hyp versions. Uses explicit host page table accessors
> instead of the kvm_* page table helpers.
> 
> Suggested-by: Christoffer Dall <christoffer.dall@xxxxxxxxxx>
> Cc: Marc Zyngier <marc.zyngier@xxxxxxx>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
> ---
> Changes since V1:
>  - Remove flush_dcache for !device_pfns in unmap_hyp_ptes()
>  - Remove huge pmd/pud checks in unmap_hyp_p.ds, since we don't
>    use huge mappings
>  - Add a comment in unmap_hyp_range() on why we don't invalidate
>    TLBs.
> ---
>  arch/arm/kvm/mmu.c |  104 +++++++++++++++++++++++++++++++++++++++++++++++++---
>  1 file changed, 99 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
> index f93f717..af526f6 100644
> --- a/arch/arm/kvm/mmu.c
> +++ b/arch/arm/kvm/mmu.c
> @@ -388,6 +388,100 @@ static void stage2_flush_vm(struct kvm *kvm)
>  	srcu_read_unlock(&kvm->srcu, idx);
>  }
>  
> +static void clear_hyp_pgd_entry(pgd_t *pgd)
> +{
> +	pud_t *pud_table __maybe_unused = pud_offset(pgd, 0UL);
> +	pgd_clear(pgd);
> +	pud_free(NULL, pud_table);
> +	put_page(virt_to_page(pgd));
> +}
> +
> +static void clear_hyp_pud_entry(pud_t *pud)
> +{
> +	pmd_t *pmd_table __maybe_unused = pmd_offset(pud, 0);
> +	VM_BUG_ON(pud_huge(*pud));
> +	pud_clear(pud);
> +	pmd_free(NULL, pmd_table);
> +	put_page(virt_to_page(pud));
> +}
> +
> +static void clear_hyp_pmd_entry(pmd_t *pmd)
> +{
> +	pte_t *pte_table = pte_offset_kernel(pmd, 0);
> +	VM_BUG_ON(pmd_thp_or_huge(*pmd));
> +	pmd_clear(pmd);
> +	pte_free_kernel(NULL, pte_table);
> +	put_page(virt_to_page(pmd));
> +}
> +
> +static void unmap_hyp_ptes(pmd_t *pmd, phys_addr_t addr, phys_addr_t end)
> +{
> +	pte_t *pte, *start_pte;
> +
> +	start_pte = pte = pte_offset_kernel(pmd, addr);
> +	do {
> +		if (!pte_none(*pte)) {
> +			kvm_set_pte(pte, __pte(0));
> +			put_page(virt_to_page(pte));
> +		}
> +	} while (pte++, addr += PAGE_SIZE, addr != end);
> +
> +	if (hyp_pte_table_empty(start_pte))
> +		clear_hyp_pmd_entry(pmd);
> +}
> +
> +static void unmap_hyp_pmds(pud_t *pud, phys_addr_t addr, phys_addr_t end)
> +{
> +	phys_addr_t next;
> +	pmd_t *pmd, *start_pmd;
> +
> +	start_pmd = pmd = pmd_offset(pud, addr);
> +	do {
> +		next = pmd_addr_end(addr, end);
> +		/* Hyp doesn't use huge pmds */
> +		if (!pmd_none(*pmd))
> +			unmap_hyp_ptes(pmd, addr, next);
> +	} while (pmd++, addr = next, addr != end);
> +
> +	if (hyp_pmd_table_empty(start_pmd))
> +		clear_hyp_pud_entry(pud);
> +}
> +
> +static void unmap_hyp_puds(pgd_t *pgd, phys_addr_t addr, phys_addr_t end)
> +{
> +	phys_addr_t next;
> +	pud_t *pud, *start_pud;
> +
> +	start_pud = pud = pud_offset(pgd, addr);
> +	do {
> +		next = pud_addr_end(addr, end);
> +		/* Hyp doesn't use huge puds */
> +		if (!pud_none(*pud))
> +			unmap_hyp_pmds(pud, addr, next);
> +	} while (pud++, addr = next, addr != end);
> +
> +	if (hyp_pud_table_empty(start_pud))
> +		clear_hyp_pgd_entry(pgd);
> +}
> +
> +static void unmap_hyp_range(pgd_t *pgdp, phys_addr_t start, u64 size)
> +{
> +	pgd_t *pgd;
> +	phys_addr_t addr = start, end = start + size;
> +	phys_addr_t next;
> +
> +	/*
> +	 * We don't unmap anything from HYP, except at the hyp tear down.
> +	 * Hence, we don't have to invalidate the TLBs here.
> +	 */
> +	pgd = pgdp + pgd_index(addr);
> +	do {
> +		next = pgd_addr_end(addr, end);
> +		if (!pgd_none(*pgd))
> +			unmap_hyp_puds(pgd, addr, next);
> +	} while (pgd++, addr = next, addr != end);
> +}
> +
>  /**
>   * free_boot_hyp_pgd - free HYP boot page tables
>   *
> @@ -398,14 +492,14 @@ void free_boot_hyp_pgd(void)
>  	mutex_lock(&kvm_hyp_pgd_mutex);
>  
>  	if (boot_hyp_pgd) {
> -		unmap_range(NULL, boot_hyp_pgd, hyp_idmap_start, PAGE_SIZE);
> -		unmap_range(NULL, boot_hyp_pgd, TRAMPOLINE_VA, PAGE_SIZE);
> +		unmap_hyp_range(boot_hyp_pgd, hyp_idmap_start, PAGE_SIZE);
> +		unmap_hyp_range(boot_hyp_pgd, TRAMPOLINE_VA, PAGE_SIZE);
>  		free_pages((unsigned long)boot_hyp_pgd, hyp_pgd_order);
>  		boot_hyp_pgd = NULL;
>  	}
>  
>  	if (hyp_pgd)
> -		unmap_range(NULL, hyp_pgd, TRAMPOLINE_VA, PAGE_SIZE);
> +		unmap_hyp_range(hyp_pgd, TRAMPOLINE_VA, PAGE_SIZE);
>  
>  	mutex_unlock(&kvm_hyp_pgd_mutex);
>  }
> @@ -430,9 +524,9 @@ void free_hyp_pgds(void)
>  
>  	if (hyp_pgd) {
>  		for (addr = PAGE_OFFSET; virt_addr_valid(addr); addr += PGDIR_SIZE)
> -			unmap_range(NULL, hyp_pgd, KERN_TO_HYP(addr), PGDIR_SIZE);
> +			unmap_hyp_range(hyp_pgd, KERN_TO_HYP(addr), PGDIR_SIZE);
>  		for (addr = VMALLOC_START; is_vmalloc_addr((void*)addr); addr += PGDIR_SIZE)
> -			unmap_range(NULL, hyp_pgd, KERN_TO_HYP(addr), PGDIR_SIZE);
> +			unmap_hyp_range(hyp_pgd, KERN_TO_HYP(addr), PGDIR_SIZE);
>  
>  		free_pages((unsigned long)hyp_pgd, hyp_pgd_order);
>  		hyp_pgd = NULL;
> -- 
> 1.7.9.5
> 

Reviewed-by: Christoffer Dall <christoffer.dall@xxxxxxxxxx>