From: Jan Beulich <jbeulich@suse.com>
To: Julien Grall <julien@xen.org>
Cc: Juergen Gross <jgross@suse.com>,
Stefano Stabellini <sstabellini@kernel.org>, Wei Liu <wl@xen.org>,
Andrew Cooper <andrew.cooper3@citrix.com>,
Julien Grall <jgrall@amazon.com>,
Ian Jackson <ian.jackson@eu.citrix.com>,
George Dunlap <george.dunlap@citrix.com>,
xen-devel@lists.xenproject.org
Subject: Re: [PATCH] pvcalls: Document explicitly the padding for all arches
Date: Mon, 20 Apr 2020 10:04:39 +0200 [thread overview]
Message-ID: <e07dbb22-1300-ae87-4065-824938caec48@suse.com> (raw)
In-Reply-To: <20200419104948.31200-1-julien@xen.org>
On 19.04.2020 12:49, Julien Grall wrote:
> --- a/docs/misc/pvcalls.pandoc
> +++ b/docs/misc/pvcalls.pandoc
> @@ -246,9 +246,7 @@ The format is defined as follows:
> uint32_t domain;
> uint32_t type;
> uint32_t protocol;
> - #ifdef CONFIG_X86_32
> uint8_t pad[4];
> - #endif
> } socket;
> struct xen_pvcalls_connect {
> uint64_t id;
> @@ -257,16 +255,12 @@ The format is defined as follows:
> uint32_t flags;
> grant_ref_t ref;
> uint32_t evtchn;
> - #ifdef CONFIG_X86_32
> uint8_t pad[4];
> - #endif
> } connect;
> struct xen_pvcalls_release {
> uint64_t id;
> uint8_t reuse;
> - #ifdef CONFIG_X86_32
> uint8_t pad[7];
> - #endif
> } release;
> struct xen_pvcalls_bind {
> uint64_t id;
> @@ -276,9 +270,7 @@ The format is defined as follows:
> struct xen_pvcalls_listen {
> uint64_t id;
> uint32_t backlog;
> - #ifdef CONFIG_X86_32
> uint8_t pad[4];
> - #endif
> } listen;
> struct xen_pvcalls_accept {
> uint64_t id;
I wonder on what grounds these #ifdef-s had been there - they're
plain wrong with the types used in the public header.
> --- a/xen/include/public/io/pvcalls.h
> +++ b/xen/include/public/io/pvcalls.h
> @@ -65,6 +65,7 @@ struct xen_pvcalls_request {
> uint32_t domain;
> uint32_t type;
> uint32_t protocol;
> + uint8_t pad[4];
> } socket;
> struct xen_pvcalls_connect {
> uint64_t id;
> @@ -73,10 +74,12 @@ struct xen_pvcalls_request {
> uint32_t flags;
> grant_ref_t ref;
> uint32_t evtchn;
> + uint8_t pad[4];
> } connect;
> struct xen_pvcalls_release {
> uint64_t id;
> uint8_t reuse;
> + uint8_t pad[7];
> } release;
> struct xen_pvcalls_bind {
> uint64_t id;
> @@ -86,6 +89,7 @@ struct xen_pvcalls_request {
> struct xen_pvcalls_listen {
> uint64_t id;
> uint32_t backlog;
> + uint8_t pad[4];
> } listen;
I'm afraid we can't change these in such a way - your additions
change sizeof() for the respective sub-structures on 32-bit x86,
and hence this is not a backwards compatible adjustment. The
best I can think of right now that we could do is make the
difference explicit, by putting the padding fields inside
#ifndef __i386__. But of course this is awkward at least when
thinking about a 32-bit / 64-bit pair of communication ends on
an x86-64 host.
Jan
next prev parent reply other threads:[~2020-04-20 8:05 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-19 10:49 [PATCH] pvcalls: Document explicitly the padding for all arches Julien Grall
2020-04-20 8:04 ` Jan Beulich [this message]
2020-04-20 13:34 ` Julien Grall
2020-04-20 13:45 ` Jan Beulich
2020-04-21 23:27 ` Stefano Stabellini
2020-04-22 9:20 ` Jan Beulich
2020-04-29 14:01 ` Julien Grall
2020-04-29 14:05 ` Jan Beulich
2020-04-29 14:14 ` Julien Grall
2020-04-29 14:56 ` Jan Beulich
2020-04-29 15:06 ` Julien Grall
2020-04-29 15:23 ` Jan Beulich
2020-04-29 15:30 ` Julien Grall
2020-04-29 15:57 ` Jan Beulich
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