Re: [Xen-devel] [PATCH v5 05/10] x86emul: support MOVDIR64B insn

[Paul Durrant <xadimgnik@xxxxxxxxx>]

> -----Original Message-----
> From: Xen-devel <xen-devel-bounces@xxxxxxxxxxxxxxxxxxxx> On Behalf Of Jan 
> Beulich
> Sent: 24 March 2020 12:34
> To: xen-devel@xxxxxxxxxxxxxxxxxxxx
> Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>; Paul Durrant 
> <Paul.Durrant@xxxxxxxxxx>; Wei Liu
> <wl@xxxxxxx>; Roger Pau Monne <roger.pau@xxxxxxxxxx>
> Subject: [Xen-devel] [PATCH v5 05/10] x86emul: support MOVDIR64B insn
> 
> Introduce a new blk() hook, paralleling the rmw() on in certain way, but
> being intended for larger data sizes, and hence its HVM intermediate
> handling function doesn't fall back to splitting the operation if the
> requested virtual address can't be mapped.
> 
> Note that SDM revision 071 doesn't specify exception behavior for
> ModRM.mod == 0b11; assuming #UD here.
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> ---
> TBD: If we want to avoid depending on correct MTRR settings,
>      hvmemul_map_linear_addr() may need to gain a parameter to allow
>      controlling cachability of the produced mapping(s).

Or could we deal with this by adding an optional cache flush into the unmap?

> Of course the
>      function will also need to be made capable of mapping at least
>      p2m_mmio_direct pages for this and the two ENQCMD insns to be
>      actually useful.


I/O emulation parts LGTM so...

Reviewed-by: Paul Durrant <paul@xxxxxxx>