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Re: [Qemu-devel] [PATCH v2 33/42] ivshmem: Implement shm=... with a memo
Re: [Qemu-devel] [PATCH v2 33/42] ivshmem: Implement shm=... with a memory backend
Thu, 10 Mar 2016 07:48:12 +0100
Gnus/5.13 (Gnus v5.13) Emacs/24.5 (gnu/linux)
Marc-André Lureau <address@hidden> writes:
> On Wed, Mar 9, 2016 at 9:59 PM, Markus Armbruster <address@hidden> wrote:
>> The integrated memory backend has to go.
>> Yes, my desugaring to memory-backend-file assumes Linux and the
>> conventional mount point /dev/shm.
>> For what it's worth, glibc implements shm_open() as a thin wrapper
>> around open() on all targets. On Linux, it looks for other mountpoints
>> when /dev/shm/ isn't there or unsuitable. On other targets, it always
>> uses /dev/shm/. I didn't bother to duplicate glibc's mountpoint search,
>> because distros converged to /dev/shm/ long ago.
>> The proper way to support POSIX shared memory objects on systems where
>> they're not files (and therefore can't be mapped with
>> memory-backend-file) is to create memory-backend-shm. If such systems
>> I didn't do this now, because one, I'm not aware of a system that needs
>> it, and two, ivshmem is Linux-specific anyway. ivshmem-plain could be
>> made more portable, and once that's done, memory-backend-shm might
>> become useful.
> How is ivshmem (the "plain" part) Linux-specific? Afaik it works on bsd too.
To make ivshmem-plain more portable, either add suitable #ifdefs to
ivshmem.c or split ivshmem-plain off into its own file. As is, we only
compile ivshmem.c with CONFIG_EVENTFD.
If someone does that work, *and* any of the systems opened up by that
can't do use memory-backend-file, then those systems would profit from
>> That leaves permissions. You're right, the patch changes them from 0777
>> to 0644. I'm inclined to call it a bug fix. I failed to mention it in
>> my commit message, and I'll fix that. We may want to mention it in
>> release notes, too.
> That's good enough for me.
[Qemu-devel] [PATCH v2 12/42] ivshmem: Rewrite specification document, Markus Armbruster, 2016/03/07
[Qemu-devel] [PATCH v2 28/42] ivshmem: Propagate errors through ivshmem_recv_setup(), Markus Armbruster, 2016/03/07
[Qemu-devel] [PATCH v2 42/42] contrib/ivshmem-server: Print "not for production" warning, Markus Armbruster, 2016/03/07
[Qemu-devel] [PATCH v2 41/42] ivshmem: Require master to have ID zero, Markus Armbruster, 2016/03/07
[Qemu-devel] [PATCH v2 07/42] event_notifier: Make event_notifier_init_fd() #ifdef CONFIG_EVENTFD, Markus Armbruster, 2016/03/07
[Qemu-devel] [PATCH v2 22/42] ivshmem: Leave INTx alone when using MSI-X, Markus Armbruster, 2016/03/07
- [Qemu-devel] [PATCH v2 25/42] ivshmem: Disentangle ivshmem_read(), (continued)