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Re: [Xen-devel] [PATCH v2] x86/hvm/ioreq: allow ioreq servers to use HVM_PARAM_[BUF]IOREQ_PFN

>>> On 09.10.18 at 10:25, <paul.durrant@xxxxxxxxxx> wrote:
> Since commit 2c257bd6 "x86/hvm: remove default ioreq server (again)" the
> GFNs allocated by the toolstack and set in HVM_PARAM_IOREQ_PFN and
> HVM_PARAM_BUFIOREQ_PFN have been unused. This patch allows them to be used
> by (non-default) ioreq servers.
> While in the area, also make sure HVM_PARAM_[BUF]IOREQ_PFN can only be set
> once. These parameters should have always been in the 'set once' category
> but this has, so far, not been enforced.
> NOTE: This fixes a compatibility issue. A guest created on a version of
>       Xen that pre-dates the initial ioreq server implementation and then
>       migrated in will currently fail to resume because its migration
>       stream will lack values for HVM_PARAM_IOREQ_SERVER_PFN and
>       HVM_PARAM_NR_IOREQ_SERVER_PAGES *unless* the system has an
>       emulator domain that uses direct resource mapping (which depends
>       on the version of privcmd it happens to have) in which case it
>       will not require use of GFNs for the ioreq server shared
>       pages.
> Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>

Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>

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