linux-kernel - Re: [PATCH 6/6] KVM: MMU: Avoid handling same rmap_pde in kvm_handle_hva

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Message-Id: <20120622233338.0e105766a0623ed7564d2c63@gmail.com>
Date:	Fri, 22 Jun 2012 23:33:38 +0900
From:	Takuya Yoshikawa <takuya.yoshikawa@...il.com>
To:	Takuya Yoshikawa <yoshikawa.takuya@....ntt.co.jp>
Cc:	avi@...hat.com, mtosatti@...hat.com, agraf@...e.de,
	paulus@...ba.org, aarcange@...hat.com, kvm@...r.kernel.org,
	kvm-ppc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 6/6] KVM: MMU: Avoid handling same rmap_pde in
 kvm_handle_hva_range()

On Thu, 21 Jun 2012 17:52:38 +0900
Takuya Yoshikawa <yoshikawa.takuya@....ntt.co.jp> wrote:

...
> +			/* Handle the first one even if idx == idx_end. */
> +			do {
> +				ret |= handler(kvm, rmapp++, data);
> +			} while (++idx < idx_end);

This is unclear and... maybe wrong.


I will change this as follows:
---
  hva_start = max(start, memslot->userspace_addr);
  hva_end = min(end, memslot->userspace_addr +
                          (memslot->npages << PAGE_SHIFT));
  if (hva_start >= hva_end)
          continue;
  /*
   * { gfn(page) | page intersects with [hva_start, hva_end) }
   * = [gfn_start, gfn_end).
   */
  gfn_start = hva_to_gfn_memslot(hva_start, memslot);
  gfn_end = hva_to_gfn_memslot(hva_end + PAGE_SIZE-1, memslot);

  for (j = PT_PAGE_TABLE_LEVEL;
       j < PT_PAGE_TABLE_LEVEL + KVM_NR_PAGE_SIZES; ++j) {
          unsigned long idx, idx_end;
          unsigned long *rmapp; 
          /*
           * { idx(page_j) | page_j intersects with [hva_start, hva_end) }
           * = [idx, idx_end].
           */
          idx = gfn_to_index(gfn_start, memslot->base_gfn, j);
          idx_end = gfn_to_index(gfn_end - 1, memslot->base_gfn, j);

          rmapp = __gfn_to_rmap(gfn_start, j, memslot);

          for (; idx <= idx_end; ++idx) {
                  ret |= handler(kvm, rmapp++, data);
          }
  }
---

This way, much clearly, we can handle exactly same rmaps as before.

I also need to change ppc code as well in patch 3.

Thanks,
	Takuya
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