Re: [Xen-devel] [PATCH v8 4/4] x86 / vmx: use a MEMF_no_refcount domheap page for APIC_DEFAULT_PHYS_BASE

["Tian, Kevin" <kevin.tian@xxxxxxxxx>]

> From: Paul Durrant <pdurrant@xxxxxxxxxx>
> Sent: Thursday, January 30, 2020 10:58 PM
> 
> vmx_alloc_vlapic_mapping() currently contains some very odd looking code
> that allocates a MEMF_no_owner domheap page and then shares with the
> guest
> as if it were a xenheap page. This then requires vmx_free_vlapic_mapping()
> to call a special function in the mm code: free_shared_domheap_page().
> 
> By using a MEMF_no_refcount domheap page instead, the odd looking code
> in
> vmx_alloc_vlapic_mapping() can simply use get_page_and_type() to set up a
> writable mapping before insertion in the P2M and
> vmx_free_vlapic_mapping()
> can simply release the page using put_page_alloc_ref() followed by
> put_page_and_type(). This then allows free_shared_domheap_page() to be
> purged.
> 
> Signed-off-by: Paul Durrant <pdurrant@xxxxxxxxxx>
> Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>

Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>
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