[PATCH v3] arm/arm64: KVM: Fix and refactor unmap_range

[Steve Capper]

Hi Christoffer,

On 4 June 2014 16:15, Christoffer Dall <christoffer.dall at linaro.org> 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.
>
> Tested on TC2 with/without THP and limited testing on the v8 Foundation
> Model.
>
> Reviewed-by: Jungseok Lee <jays.lee at samsung.com>
> Reviewed-by: Mario Smarduch <m.smarduch at samsung.com>
> Acked-by: Marc Zyngier <marc.zyngier at arm.com>
> Signed-off-by: Christoffer Dall <christoffer.dall at linaro.org>
> ---

This looks good to me.

Reviewed-by: Steve Capper <steve.capper at linaro.org>

One minor comment below (sorry just spotted this now)...

[ ... ]

> -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,
> +                      phys_addr_t addr, phys_addr_t end)
>  {
> -       if (pte_present(*pte)) {
> -               kvm_set_pte(pte, __pte(0));
> -               put_page(virt_to_page(pte));
> -               kvm_tlb_flush_vmid_ipa(kvm, addr);
> -       }
> +       pte_t *pte, *start_pte;
> +       unsigned long long start_addr = addr;
> +
> +       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));
> +                       kvm_tlb_flush_vmid_ipa(kvm, addr);

Can this hyp call be expensive if a lot of ptes are being unmapped
(for 64K pages we can have 8192 ptes per page)?
If so, can they be batched together?

Cheers,
-- 
Steve