Re: [Xen-devel] [PATCH 5/3] x86/shadow: emulate_gva_to_mfn() should respect p2m_ioreq_server

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> Sent: 13 November 2018 10:47
> To: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
> Cc: Andrew Cooper <Andrew.Cooper3@xxxxxxxxxx>; Paul Durrant
> <Paul.Durrant@xxxxxxxxxx>; Wei Liu <wei.liu2@xxxxxxxxxx>; Tim (Xen.org)
> <tim@xxxxxxx>
> Subject: [PATCH 5/3] x86/shadow: emulate_gva_to_mfn() should respect
> p2m_ioreq_server
> 
> Writes to such pages would need to be handed to the emulator, which we're
> not prepared to do at this point.
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> 
> --- a/xen/arch/x86/mm/shadow/hvm.c
> +++ b/xen/arch/x86/mm/shadow/hvm.c
> @@ -338,7 +338,7 @@ static mfn_t emulate_gva_to_mfn(struct v
>      {
>          return _mfn(BAD_GFN_TO_MFN);
>      }
> -    if ( p2m_is_discard_write(p2mt) )
> +    if ( p2m_is_discard_write(p2mt) || p2mt == p2m_ioreq_server )
>      {
>          put_page(page);
>          return _mfn(READONLY_GFN);

Is this what we want here? I would have thought we want to return 
BAD_GFN_TO_MFN in the p2m_ioreq_server case so that the caller treats this in 
the same way it would MMIO.

  Paul

> 


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