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

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 and
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 patch
(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...

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?


Julien Grall



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