Re: [Qemu-devel] [PATCH v2 1/4] hostmem-memfd: disable for systems wihtout sealing support

[Daniel P . Berrangé]

On Tue, Nov 27, 2018 at 04:50:27PM +0300, Ilya Maximets wrote:
> If seals are not supported, memfd_create() will fail.
> Furthermore, there is no way to disable it in this case because
> '.seal' property is not registered.

Isn't the real problem here that memfd_backend_instance_init() has
unconditionally set  "m->seal = true"

Surely, if we don't register the '.seal' property, we should default
that flag to false.

> 
> This issue leads to vhost-user-test failures on RHEL 7.2:
> 
>   qemu-system-x86_64: -object memory-backend-memfd,id=mem,size=2M,: \
>                       failed to create memfd: Invalid argument
> 
> and actually breaks the feature on such systems.
> 
> Let's restrict memfd backend to systems with sealing support.

I don't think we need todo that - sealing is optional in the QEMU code,
we simply have it set to the wrong default when sealing is not available.

> Signed-off-by: Ilya Maximets <address@hidden>


Regards,
Daniel
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