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Re: [Xen-devel] Regression: x86/mm: new _PTE_SWP_SOFT_DIRTY bit conflicts with existing use
- To: Cyrill Gorcunov <gorcunov@xxxxxxxxx>
- From: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
- Date: Wed, 21 Aug 2013 16:04:54 -0700
- Cc: Pavel Emelyanov <xemul@xxxxxxxxxxxxx>, "linux-kernel@xxxxxxxxxxxxxxx" <linux-kernel@xxxxxxxxxxxxxxx>, Andy Lutomirski <luto@xxxxxxxxxxxxxx>, Ingo Molnar <mingo@xxxxxxxxxx>, David Vrabel <david.vrabel@xxxxxxxxxx>, Jan Beulich <JBeulich@xxxxxxxx>, "H. Peter Anvin" <hpa@xxxxxxxxx>, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>, Xen-devel@xxxxxxxxxxxxx, Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
- Delivery-date: Wed, 21 Aug 2013 23:05:24 +0000
- List-id: Xen developer discussion <xen-devel.lists.xen.org>
On Wed, Aug 21, 2013 at 12:03 PM, Cyrill Gorcunov <gorcunov@xxxxxxxxx> wrote:
>
> I personally don't see bug here because
>
> - this swapped page soft dirty bit is set for non-present entries only,
> never for present ones, just at moment we form swap pte entry
>
> - i don't find any code which would test for this bit directly without
> is_swap_pte call
Ok, having gone through the places that use swp_*soft_dirty(), I have
to agree. Afaik, it's only ever used on a swap-entry that has (by
definition) the P bit clear. So with or without Xen, I don't see how
it can make any difference.
David/Konrad - did you actually see any issues, or was this just from
(mis)reading the code?
Linus
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