Re: [PATCH] x86/pv: Inline domain_set_alloc_bitsize() into it's single caller

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 09/12/2025 7:29 pm, Andrew Cooper wrote:
> On 09/12/2025 7:21 pm, Grygorii Strashko wrote:
>> Hi Andrew,
>>
>> On 09.12.25 20:07, Andrew Cooper wrote:
>>> Prior to commit 02e78311cdc6 ("x86/domctl: Make
>>> XEN_DOMCTL_set_address_size
>>> singleshot") (Xen 4.9, 2016), it was possible for domains to switch
>>> to being
>>> compat, and back again.  Since then however, becoming compat is a
>>> singleton
>>> action that can't be undone.
>>>
>>>  From the context it's clear to see the is_pv_32bit_domain() check is
>>> redundant, and from the singleton nature being the only place setting
>>> physaddr_bitsize, there's no need to check it for being 0.
>>>
>>> No functional change.
>>>
>>> Co-developed-by: Grygorii Strashko <grygorii_strashko@xxxxxxxx>
>>> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
>>> ---
>>> CC: Jan Beulich <JBeulich@xxxxxxxx>
>>> CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
>>> CC: Grygorii Strashko <grygorii_strashko@xxxxxxxx>
>>>
>>> Split out of series to simplify things.
>>>
>>> bloat-o-meter reports:
>>>
>>>    add/remove: 0/1 grow/shrink: 1/0 up/down: 25/-96 (-71)
>>>    Function                                     old     new   delta
>>>    switch_compat                                447     472     +25
>>>    domain_set_alloc_bitsize                      96       -     -96
>>>
>>> which will mostly be the LFENCEs embedded in is_pv_32bit_domain().
>> Thank you for doing this.
>> Not sure if it's needed, any way.
>> Reviewed-by: Grygorii Strashko <grygorii_strashko@xxxxxxxx>
> It does help.  Technically it lets me commit the patch right now, but
> I'll leave it until at least tomorrow in case anyone else has comments.
>
> ~Andrew
>

FYI, here is the remainder of your patch rebased over this one.

I recommend splitting it into two, one sorting out
domain_clamp_alloc_bitsize() (however that will end up looking), and one
moving physaddr_bitsize into pv_domain.

It's almost always better to separate code movement from logical changes.

~Andrew

Attachment: 0001-xen-x86-move-d-arch.physaddr_bitsize-field-handling-.patch
Description: Text Data