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[Xen-devel] [PATCH] libxc/restore: Don't duplicate state in process_vcpu_basic()

  • To: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
  • From: Ian Jackson <ian.jackson@xxxxxxxxxx>
  • Date: Fri, 20 Dec 2019 18:22:39 +0000
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  • Cc: Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Wei Liu <wl@xxxxxxx>
  • Delivery-date: Fri, 20 Dec 2019 18:22:58 +0000
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  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

Andrew Cooper writes ("[PATCH] libxc/restore: Don't duplicate state in 
> vcpu_guest_context_any_t is currently allocated on the stack, and copied from
> a mutable buffer which is freed immediately after its use here.
> Mutate the buffer in place instead of duplicating it.

It is not obvious to me that nothing uses the modified fields after
process_vcpu_basic has edited things.  The ctx of which the vcpu is
part is passed to process_vcpu_<various> by update_vcpu_context.

Why do you think this copying (which is extra code) was introduced ?


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