[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [PATCH] stubdom: foreignmemory: Fix build after 0dbb4be739c5

On 13/07/2021 13:39, Andrew Cooper wrote:
On 13/07/2021 12:53, Julien Grall wrote:
Hi Andrew,

On 13/07/2021 12:23, Andrew Cooper wrote:
On 13/07/2021 12:21, Julien Grall wrote:
Hi Andrew,

On 13/07/2021 10:35, Andrew Cooper wrote:
On 13/07/2021 10:27, Juergen Gross wrote:
On 13.07.21 11:20, Julien Grall wrote:
From: Julien Grall <jgrall@xxxxxxxxxx>

Commit 0dbb4be739c5 add the inclusion of xenctrl.h from private.h
wreck the build in an interesting way:

In file included from xen/stubdom/include/xen/domctl.h:39:0,
                     from xen/tools/include/xenctrl.h:36,
                     from private.h:4,
                     from minios.c:29:
xen/include/public/memory.h:407:5: error: expected
specifier-qualifier-list before ‘XEN_GUEST_HANDLE_64’
         XEN_GUEST_HANDLE_64(const_uint8) buffer;

This is happening because xenctrl.h defines __XEN_TOOLS__ and
the public headers will start to expose the non-stable ABI. However,
xen.h has already been included by a mini-OS header before hand. So
there is a mismatch in the way the headers are included.

For now solve it in a very simple (and gross) way by including
xenctrl.h before the mini-os headers.

Fixes: 0dbb4be739c5 ("tools/libs/foreignmemory: Fix PAGE_SIZE
redefinition error")
Signed-off-by: Julien Grall <jgrall@xxxxxxxxxx>


Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

I couldn't find a better way with would not result to revert the
(and break build on some system) or involve a longer rework of the

Just adding a "#define __XEN_TOOLS__" before the #include statements
doesn't work?

Not really, no.

libxenforeignmem has nothing at all to do with any Xen unstable
interfaces.  Including xenctrl.h in the first place was wrong, because
it is an unstable library.  By extension, the use of XC_PAGE_SIZE is
also wrong.

Well... Previously we were using PAGE_SIZE which is just plain wrong
on Arm.

At the moment, we don't have a way to query the page granularity of
the hypervisor. But we know it can't change because of the way the
current ABI was designed. Hence why using XC_PAGE_SIZE is the best of
option we had until we go to ABIv2.

Still doesn't mean that XC_PAGE_SIZE was ok to use.

Note that I wrote "best of the option". The series has been sitting
for ages with no-one answering... You could have provided your option
back then if you thought it wasn't a good use...

On a series I wasn't even CC'd on?

You had the link on IRC because we discussed it.

And noone had even bothered to compile test?

Well, that was a mistake. At the same time, if it compiled the "issue" you describe would have gone unnoticed. ;)

Sounds like the constant needs moving into the Xen public headers, and
the inclusions of xenctrl.h into stable libraries needs reverting.

This could work. Are you planning to work on it?

No.  I don't have enough time to do my own work thanks to all the CI
breakage and regressions being committed.
This needs fixing, or the original series reverting for 4.16 because the
current form (with or without this emergency build fix) isn't acceptable
to release with.
I disagree with this caracterization. Yes, this is including a non-stable header but it doesn't link with non-stable library.

In fact, reverting the series will bring back two issues:
  1) Xen tools will not build on all the distros
2) Using PAGE_{SIZE, SHIFT} break arm tools because the userspace is not meant to rely on a given kernel page granularity.

So this doesn't look like a priority for 4.16. Although, it would be a nice clean-up to have so the libraries are more compliant.


Julien Grall



Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.