Re: [Xen-devel] [PATCH] build: convert CONFIG_COMPAT to Kconfig

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 18.12.15 at 23:09, <andrew.cooper3@xxxxxxxxxx> wrote:
> On 18/12/2015 21:49, Doug Goldstein wrote:
>> On 12/18/15 3:35 PM, Andrew Cooper wrote:
>>> On 18/12/2015 20:06, Doug Goldstein wrote:
>>>> Use the Kconfig generated CONFIG_COMPAT defines in the code base.
>>>>
>>>> CC: Keir Fraser <keir@xxxxxxx>
>>>> CC: Jan Beulich <jbeulich@xxxxxxxx>
>>>> CC: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
>>>> Signed-off-by: Doug Goldstein <cardoe@xxxxxxxxxx>
>>> Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, although I have
>>> a slight quibble.
>>>
>>>> ---
>>>> This was previously Acked-by: Jan Beulich <jbeulich@xxxxxxxx> but then
>>>> there was a request to change it to xen/common/Kconfig from
>>>> xen/arch/x86/Kconfig. Unfortunately a small typo ('def_bool y' instead of
>>>> 'bool') caused it to break on ARM. This resolves the issue and should be
>>>> ready to merge.
>>>> ---
>>>>  config/x86_64.mk     | 1 -
>>>>  xen/arch/x86/Kconfig | 1 +
>>>>  xen/common/Kconfig   | 7 +++++++
>>>>  3 files changed, 8 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/config/x86_64.mk b/config/x86_64.mk
>>>> index f12d549..85fa27c 100644
>>>> --- a/config/x86_64.mk
>>>> +++ b/config/x86_64.mk
>>>> @@ -2,7 +2,6 @@ CONFIG_X86 := y
>>>>  CONFIG_X86_64 := y
>>>>  CONFIG_X86_$(XEN_OS) := y
>>>>  
>>>> -CONFIG_COMPAT := y
>>>>  CONFIG_MIGRATE := y
>>>>  CONFIG_XCUTILS := y
>>>>  
>>>> diff --git a/xen/arch/x86/Kconfig b/xen/arch/x86/Kconfig
>>>> index 07e366d..7d2ed96 100644
>>>> --- a/xen/arch/x86/Kconfig
>>>> +++ b/xen/arch/x86/Kconfig
>>>> @@ -3,6 +3,7 @@ config X86_64
>>>>  
>>>>  config X86
>>>>    def_bool y
>>>> +  select COMPAT
>>>>    select HAS_ACPI
>>>>    select HAS_CPUFREQ
>>>>    select HAS_EHCI
>>>> diff --git a/xen/common/Kconfig b/xen/common/Kconfig
>>>> index 7d0e9a9..046e257 100644
>>>> --- a/xen/common/Kconfig
>>>> +++ b/xen/common/Kconfig
>>>> @@ -1,6 +1,13 @@
>>>>  
>>>>  menu "Common Features"
>>>>  
>>>> +config COMPAT
>>>> +  bool
>>>> +  help
>>>> +    32-bit interface support on 64-bit Xen which is used for both
>>>> +    HVM and PV guests. HVMLoader makes 32-bit hypercalls irrespective
>>>> +    of the destination runmode of the guest.
>>> As this is now common, probably want to specify x86 HVM and PV guests. 
>>> Arm guests are technically HVM, although the term is rather less common
>>> on their side.
>>>
>>> ~Andrew
>>>
>> How about:
>>
>> 32-bit interface support on 64-bit Xen which is used by x86 HVM and PV
>> guests and ARM HVM guests. The reason this is used for HVM guests is
>> that HVMLoader makes 32-bit hypercalls irrespective of the destination
>> run mode of the guest.
>>
> 
> The complication here is that arm doesn't yet support compat.  There is
> a hope to (which is, I guess, why Jan asked for it to be common), but it
> shouldn't give any implication that it is available on ARM yet.

I don't think ARM is meant to ever use this layer - its interface was
made 32-bit clean from the beginning. The reason for wanting this
option to be common is an abstract one (i.e. considering just possible
future architectures).

Jan


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