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[Xen-devel] Xc_mem_access_enable_emulate() is currently a no-operation

  • To: "xen-devel@xxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxx>, "Lengyel, Tamas" <tlengyel@xxxxxxxxxxx>
  • From: Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>
  • Date: Mon, 7 Dec 2015 11:09:38 +0200
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  • Delivery-date: Mon, 07 Dec 2015 09:09:16 +0000
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While looking at some code with Tamas these past few days, we discovered
that xc_mem_access_enable_emulate() doesn't actually do anything other
that setting the mem_access_emulate_enabled flag.

Fixing that would likely be trivial (if the flag is not set,
p2m_mem_access_emulate_check() should just return). However, my question
is: do we really need that function? Are there cases where it would make
sense to use the vm_event subsystem but disable emulation support? After
all, if the client code wants to use emulation support it can call
xc_mem_access_enable_emulate(), and if not it can simply not set the
EMULATE flags in the vm_event replies.

As far as I'm concerned, the libxc function can go (along with the
per-domain flag), but then again we're emulation-intensive so it's quite
possible that I'm not seeing the proper use case for this.



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