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Re: [Qemu-devel] [PATCH qemu v7 06/14] spapr_iommu: Introduce "enabled"

From: Alexey Kardashevskiy
Subject: Re: [Qemu-devel] [PATCH qemu v7 06/14] spapr_iommu: Introduce "enabled" state for TCE table
Date: Tue, 26 May 2015 23:28:44 +1000
User-agent: Mozilla/5.0 (X11; Linux i686 on x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0

On 05/26/2015 10:50 PM, Paolo Bonzini wrote:

On 26/05/2015 14:33, Alexey Kardashevskiy wrote:

If it's not true now that they can be unparented at any time like
alias regions, we should probably try to make it true.

Unfortunately it's not so easy...

Uff. Tricky :)

memory_region_del_subregion() is not unparenting but just a wrapped
object_unref(), right?

Right.  The problematic thing to do is explicit object_unparent followed
by one of the following:

1) memory_region_init for the same memory region that has been unparented

2) g_free of some dynamically-allocated data structure that contained
the memory region.

But since iommu MR are resolved dynamically, the
whole conversation we are having here now has nothing to do with my&Mike
concern what we can and cannot do with DMA windows here. Is this correct?

I don't understand what you're asking here, sorry.

My initial concern was if I can or cannot do:

memory_region_init_iommu + memory_region_add_subregion
memory_region_del_subregion + object_unref

outside of init/realize/unrealize/finalize.

You said I cannot do unparenting but as I am not doing this (and I just do unref()) - I am fine. That's what I meant.


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