Re: [Xen-devel] [PATCH] xen/hvm: Fix handling of obsolete HVM_PARAMs

[Tamas K Lengyel <tamas@xxxxxxxxxxxxx>]

On Thu, Feb 6, 2020 at 6:24 AM Andrew Cooper <andrew.cooper3@xxxxxxxxxx> wrote:
>
> The local xc_hvm_param_deprecated_check() in libxc tries to guess Xen's
> behaviour for the MEMORY_EVENT params, but is wrong for the get side, where
> Xen would return 0 (which is also a bug).  Delete the helper.
>
> In Xen, perform the checks in hvm_allow_set_param(), rather than
> hvm_set_param(), and actually implement checks on the get side so the
> hypercall doesn't return successfully with 0 as an answer.
>
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> ---
> CC: Jan Beulich <JBeulich@xxxxxxxx>
> CC: Wei Liu <wl@xxxxxxx>
> CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> CC: Ian Jackson <Ian.Jackson@xxxxxxxxxx>
> CC: Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>
> CC: Tamas K Lengyel <tamas@xxxxxxxxxxxxx>
>
> Tamas: You introduced xc_hvm_param_deprecated_check() in 0a246b41ca while
> introducing XEN_DOMCTL_monitor_op.  Do you recall why?

Well, from the looks of it the intent was to tell any remaining user
of the deprecated HVM params that these are no longer supported since
we now have a separate domctl, the monitor_op, to set these options.

Tamas

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