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From: Andrew Cooper <andrew.cooper3@citrix.com>
To: Jan Beulich <jbeulich@suse.com>,
	"xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>
Cc: George Dunlap <george.dunlap@citrix.com>,
	Ian Jackson <iwj@xenproject.org>, Julien Grall <julien@xen.org>,
	Stefano Stabellini <sstabellini@kernel.org>, Wei Liu <wl@xen.org>
Subject: Re: [PATCH 4/9] gnttab: drop GNTMAP_can_fail
Date: Thu, 26 Aug 2021 12:45:04 +0100	[thread overview]
Message-ID: <871a58f1-e978-6046-db37-037ec18dbb9d@citrix.com> (raw)
In-Reply-To: <761f3ea8-bfc9-4a8b-7878-2ff9e3047309@suse.com>

On 26/08/2021 11:13, Jan Beulich wrote:
> There's neither documentation of what this flag is supposed to mean, nor
> any implementation. With this, don't even bother enclosing the #define-s
> in a __XEN_INTERFACE_VERSION__ conditional, but drop them altogether.
>
> Signed-off-by: Jan Beulich <jbeulich@suse.com>

It was introduced in 4d45702cf0398 along with GNTST_eagain, and the
commit message hints that it is for xen-paging

Furthermore, the first use of GNTST_eagain was in ecb35ecb79e0 for
trying to map/copy a paged-out frame.

Therefore I think it is reasonable to conclude that there was a planned
interaction between GNTMAP_can_fail and paging, which presumably would
have been "don't pull this in from disk if it is paged out".


I think it is fine to drop, as no implementation has ever existed in
Xen, but it would be helpful to have the history summarised in the
commit message.

~Andrew



  reply	other threads:[~2021-08-26 11:45 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-26 10:06 [PATCH 0/9] gnttab: further work from XSA-380 / -382 context Jan Beulich
2021-08-26 10:09 ` [PATCH 1/9] gnttab: defer allocation of maptrack frames table Jan Beulich
2021-09-06 13:13   ` Julien Grall
2021-09-06 13:29     ` Jan Beulich
2021-09-06 13:33       ` Julien Grall
2021-09-06 13:58         ` Jan Beulich
2021-09-06 14:05   ` Andrew Cooper
2021-09-06 14:43     ` Jan Beulich
2021-08-26 10:11 ` [PATCH 2/9] gnttab: drop a redundant expression from gnttab_release_mappings() Jan Beulich
2021-09-06 13:15   ` Julien Grall
2021-08-26 10:12 ` [PATCH 3/9] gnttab: fold recurring is_iomem_page() Jan Beulich
2021-09-06 13:35   ` Julien Grall
2021-09-06 14:02     ` Jan Beulich
2021-08-26 10:13 ` [PATCH 4/9] gnttab: drop GNTMAP_can_fail Jan Beulich
2021-08-26 11:45   ` Andrew Cooper [this message]
2021-08-26 13:03     ` Jan Beulich
2021-08-26 13:13       ` Andrew Cooper
2021-08-26 10:13 ` [PATCH 5/9] gnttab: defer allocation of status frame tracking array Jan Beulich
2021-08-26 10:13 ` [PATCH 6/9] gnttab: check handle early in gnttab_get_status_frames() Jan Beulich
2021-09-06 13:41   ` Julien Grall
2021-08-26 10:14 ` [PATCH 7/9] gnttab: no need to translate handle for gnttab_get_status_frames() Jan Beulich
2022-10-07 18:24   ` Andrew Cooper
2021-08-26 10:14 ` [PATCH 8/9] gnttab: bail from GFN-storing loops early in case of error Jan Beulich
2022-10-07 19:36   ` Andrew Cooper
2022-10-10  9:30     ` Jan Beulich
2021-08-26 10:15 ` [PATCH 9/9] gnttab: don't silently truncate GFNs in compat setup-table handling Jan Beulich
2022-10-07 19:57   ` Andrew Cooper
2022-10-10  8:46     ` Jan Beulich
2022-01-05  7:42 ` Ping: [PATCH 0/9] gnttab: further work from XSA-380 / -382 context Jan Beulich
2022-10-07 13:49 ` Jan Beulich
2022-10-07 18:09   ` Andrew Cooper

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