[libvirt] [PATCH 8/8] qemu: set qemu process' RLIMIT_MEMLOCK when VFIO is used

[Eric Blake]

On 04/25/2013 11:57 AM, Laine Stump wrote:
> VFIO requires all of the guest's memory and IO space to be lockable in
> RAM. The domain's max_balloon is the maximum amount of memory the
> domain can have (in KiB). We add a generous 1GiB to that for IO space
> (still much better than KVM device assignment, where the KVM module
> actually *ignores* the process limits and locks everything anyway),
> and convert from KiB to bytes.
> 
> In the case of hotplug, we are changing the limit for the already
> existing qemu process (prlimit() is used under the hood), and for
> regular commandline additions of vfio devices, we schedule a call to
> setrlimit() that will happen after the qemu process is forked.
> ---
>  src/qemu/qemu_command.c | 22 +++++++++++++++-------
>  src/qemu/qemu_hotplug.c | 24 +++++++++++++++++-------
>  2 files changed, 32 insertions(+), 14 deletions(-)
> 
> +                /* VFIO requires all of the guest's memory to be
> +                 * locked resident, plus some amount for IO
> +                 * space. Alex Williamson suggested adding 1GiB for IO
> +                 * space just to be safe (some finer tuning might be
> +                 * nice, though).
> +                 */
> +                virCommandSetMaxMemLock(cmd, ((unsigned long long)def->mem.max_balloon + (1024 * 1024)) * 1024);

Worth wrapping the long line, perhaps at the + operator?  Or even using
a temporary:
unsigned long long mem_kbytes = def->mem.max_balloon + (1024 * 1024);
virCommandSetMaxMemLock(cmd, mem_kbytes * 1024);

> +        virSetMaxMemLock(vm->pid,
> +                         ((unsigned long long)vm->def->mem.max_balloon + (1024 * 1024)) * 1024);

and again.  Line wrapping is trivial, though, so:

ACK.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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