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Re: [Xen-devel] Regression: x86/mm: new _PTE_SWP_SOFT_DIRTY bit conflicts with existing use
- To: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
- From: Dave Jones <davej@xxxxxxxxxx>
- Date: Wed, 21 Aug 2013 20:51:15 -0400
- Cc: Pavel Emelyanov <xemul@xxxxxxxxxxxxx>, "linux-kernel@xxxxxxxxxxxxxxx" <linux-kernel@xxxxxxxxxxxxxxx>, Andy Lutomirski <luto@xxxxxxxxxxxxxx>, Cyrill Gorcunov <gorcunov@xxxxxxxxx>, dhillf@xxxxxxxxx, 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: Thu, 22 Aug 2013 00:52:01 +0000
- List-id: Xen developer discussion <xen-devel.lists.xen.org>
- Mail-followup-to: Dave Jones <davej@xxxxxxxxxx>, Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>, Cyrill Gorcunov <gorcunov@xxxxxxxxx>, "H. Peter Anvin" <hpa@xxxxxxxxx>, David Vrabel <david.vrabel@xxxxxxxxxx>, Jan Beulich <JBeulich@xxxxxxxx>, Andy Lutomirski <luto@xxxxxxxxxxxxxx>, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>, Xen-devel@xxxxxxxxxxxxx, Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>, Pavel Emelyanov <xemul@xxxxxxxxxxxxx>, Ingo Molnar <mingo@xxxxxxxxxx>, "linux-kernel@xxxxxxxxxxxxxxx" <linux-kernel@xxxxxxxxxxxxxxx>, dhillf@xxxxxxxxx
On Wed, Aug 21, 2013 at 04:04:54PM -0700, Linus Torvalds wrote:
> 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?
Could this explain what I'm seeing in another thread ?
https://lkml.org/lkml/2013/8/7/27
Dave
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