From: Andrew Cooper <andrew.cooper3@citrix.com>
To: Jan Beulich <jbeulich@suse.com>,
"xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>
Cc: "Wei Liu" <wl@xen.org>, "Roger Pau Monné" <roger.pau@citrix.com>,
"Juergen Gross" <jgross@suse.com>,
"George Dunlap" <george.dunlap@citrix.com>,
"Ian Jackson" <iwj@xenproject.org>
Subject: Re: [PATCH v2 03/13] libxenguest: deal with log-dirty op stats overflow
Date: Mon, 5 Jul 2021 16:41:38 +0100 [thread overview]
Message-ID: <c5e7aa43-1023-ff6f-e882-0ced8af81613@citrix.com> (raw)
In-Reply-To: <668ef720-389f-4cf1-608e-64aca4f7c73d@suse.com>
On 05/07/2021 16:13, Jan Beulich wrote:
> In send_memory_live() the precise value the dirty_count struct field
> gets initialized to doesn't matter much (apart from the triggering of
> the log message in send_dirty_pages(), see below), but it is important
> that it not be zero on the first iteration (or else send_dirty_pages()
> won't get called at all). Saturate the initializer value at the maximum
> value the field can hold.
I've already explained why this is broken...
> While there also initialize struct precopy_stats' respective field to a
> more sane value: We don't really know how many dirty pages there are at
> that point.
>
> In suspend_and_send_dirty() and verify_frames() the local variables
> don't need initializing at all, as they're only an output from the
> hypercall which gets invoked first thing.
>
> In send_checkpoint_dirty_pfn_list() the local variable can be dropped
> altogether: It's optional to xc_logdirty_control() and not used anywhere
> else.
... and why this is broken particularly in the context of a later
change, and ...
>
> Note that in case the clipping actually takes effect, the "Bitmap
> contained more entries than expected..." log message will trigger. This
> being just an informational message, I don't think this is overly
> concerning.
... why this isn't ok.
Why do I bother wasting my time reviewing patches in the first place.
~Andrew
next prev parent reply other threads:[~2021-07-05 15:42 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-05 15:09 [PATCH v2 00/13] x86: more or less log-dirty related improvements Jan Beulich
2021-07-05 15:11 ` [PATCH v2 01/13] libxl/x86: check return value of SHADOW_OP_SET_ALLOCATION domctl Jan Beulich
2021-07-16 13:03 ` Anthony PERARD
2021-07-05 15:12 ` [PATCH v2 02/13] libxc: split xc_logdirty_control() from xc_shadow_control() Jan Beulich
2021-08-19 9:11 ` Juergen Gross
2021-08-19 9:24 ` Jan Beulich
2021-08-19 9:50 ` Juergen Gross
2021-09-02 17:04 ` [PATCH v2 02/13] libxc: split xc_logdirty_control() from xc_shadow_control() [and 1 more messages] Ian Jackson
2021-07-05 15:13 ` [PATCH v2 03/13] libxenguest: deal with log-dirty op stats overflow Jan Beulich
2021-07-05 15:41 ` Andrew Cooper [this message]
2021-07-05 15:53 ` Jan Beulich
2021-07-05 17:26 ` Olaf Hering
2021-07-06 6:39 ` Jan Beulich
2021-07-06 6:46 ` Olaf Hering
2021-07-06 6:58 ` Jan Beulich
2021-07-06 7:15 ` Olaf Hering
2021-08-19 10:20 ` Juergen Gross
2021-08-19 11:06 ` Jan Beulich
2021-08-19 11:25 ` Juergen Gross
2021-08-19 11:51 ` Jan Beulich
2021-08-19 11:53 ` Jan Beulich
2021-09-02 16:57 ` Ian Jackson
2021-08-19 14:29 ` Juergen Gross
2021-07-05 15:13 ` [PATCH v2 04/13] libxenguest: short-circuit "all-dirty" handling Jan Beulich
2021-08-19 14:21 ` Juergen Gross
2021-07-05 15:14 ` [PATCH v2 05/13] libxenguest: avoid allocating unused deferred-pages bitmap Jan Beulich
2021-08-19 14:22 ` Juergen Gross
2021-07-05 15:14 ` [PATCH v2 06/13] libxenguest: complete loops in xc_map_domain_meminfo() Jan Beulich
2021-07-05 15:15 ` [PATCH v2 07/13] libxenguest: guard against overflow from too large p2m when checkpointing Jan Beulich
2021-07-05 15:15 ` [PATCH v2 08/13] libxenguest: fix off-by-1 in colo-secondary-bitmap merging Jan Beulich
2021-07-05 15:15 ` [PATCH v2 09/13] libxenguest: restrict PV guest size Jan Beulich
2021-07-05 15:16 ` [PATCH v2 10/13] libxc: simplify HYPERCALL_BUFFER() Jan Beulich
2021-07-05 15:47 ` Andrew Cooper
2021-07-05 15:17 ` [PATCH v2 11/13] x86/paging: supply more useful log-dirty page count Jan Beulich
2021-07-05 15:18 ` [PATCH v2 12/13] x86/mm: update log-dirty bitmap when manipulating P2M Jan Beulich
2021-07-05 15:18 ` [PATCH v2 13/13] SUPPORT.md: write down restriction of 32-bit tool stacks Jan Beulich
2021-07-14 18:16 ` Julien Grall
2021-07-15 6:38 ` Jan Beulich
2021-07-15 9:05 ` Julien Grall
2021-07-15 11:36 ` Jan Beulich
2021-07-16 7:50 ` Julien Grall
2021-07-19 7:46 ` Ping: [PATCH v2 00/13] x86: more or less log-dirty related improvements Jan Beulich
2021-08-13 9:24 ` Jan Beulich
2021-08-20 7:20 ` Jan Beulich
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