From: "Jan Beulich" <JBeulich@suse.com>
To: Razvan Cojocaru <rcojocaru@bitdefender.com>
Cc: Wei Liu <wei.liu2@citrix.com>,
George Dunlap <George.Dunlap@eu.citrix.com>,
Andrew Cooper <andrew.cooper3@citrix.com>,
george.dunlap@citrix.com,
xen-devel <xen-devel@lists.xenproject.org>,
Roger Pau Monne <roger.pau@citrix.com>
Subject: Re: [PATCH V10 4/5] p2m: Always use hostp2m when clipping rangesets
Date: Tue, 04 Dec 2018 05:54:01 -0700 [thread overview]
Message-ID: <5C0678E90200007800202AD6@prv1-mh.provo.novell.com> (raw)
In-Reply-To: <f1ae1d45-18d4-5266-a895-372449e1b14e@bitdefender.com>
>>> On 04.12.18 at 13:18, <rcojocaru@bitdefender.com> wrote:
> Right, so you're saying that the series would be able to go in provided
> that the situation is not made worse than it currently is.
Well, I'm not the maintainer of this code, so in principle the
series can go in despite my reservations.
> As far as I can tell, the patch changes nothing functionally from the
> current state of affairs: when called for the hostp2m it behaves exactly
> the same.
>
> The one difference is the early return, which is certainly not making
> things worse: rangeset_add_range() will crash the hypervisor in an
> ASSERT(start <= end). It just happened that that never occured for the
> hostp2m - so it will continue to not happen for the hostp2m.
>
> Could you please provide more details on the case that is making things
> worse? Which cases of "start" (if that is what you mean) make things worse?
Okay, I've looked again - start indeed doesn't get clipped. Yet the
added return path plus the comment next to it still make the
situation worse imo, as they further the impression that the clipping
of end is correct. Or in other words, with the change it'll be less
visible that there's a (perhaps just theoretical, as said) bug here.
Hence my desire to get the bug addressed while this code is
being basically re-done anyway.
Jan
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next prev parent reply other threads:[~2018-12-04 12:54 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-28 21:56 [PATCH V10 0/5] Fix VGA logdirty related display freezes with altp2m Razvan Cojocaru
2018-11-28 21:56 ` [PATCH V10 1/5] x86/p2m: allocate logdirty_ranges for altp2ms Razvan Cojocaru
2018-11-28 21:56 ` [PATCH V10 2/5] x86/p2m: refactor p2m_reset_altp2m() Razvan Cojocaru
2018-11-28 21:56 ` [PATCH V10 3/5] x86/altp2m: fix display frozen when switching to a new view early Razvan Cojocaru
2018-11-28 21:56 ` [PATCH V10 4/5] p2m: Always use hostp2m when clipping rangesets Razvan Cojocaru
2018-11-29 10:04 ` Jan Beulich
2018-11-29 13:23 ` Razvan Cojocaru
2018-11-29 13:58 ` Jan Beulich
2018-11-30 21:59 ` Razvan Cojocaru
2018-12-03 8:49 ` Jan Beulich
2018-12-04 12:18 ` Razvan Cojocaru
2018-12-04 12:54 ` Jan Beulich [this message]
2018-12-04 14:05 ` Razvan Cojocaru
2018-11-28 21:56 ` [PATCH V10 5/5] p2m: change_type_range: Only invalidate mapped gfns Razvan Cojocaru
2018-11-28 22:01 ` Razvan Cojocaru
2018-11-29 10:07 ` Jan Beulich
2018-11-29 11:47 ` Razvan Cojocaru
2018-12-04 3:27 ` [PATCH V10 0/5] Fix VGA logdirty related display freezes with altp2m Tamas K Lengyel
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