On 16.05.2025 10:27, Roger Pau Monné wrote: > On Fri, May 16, 2025 at 10:08:35AM +0200, Jan Beulich wrote: >> On 16.05.2025 10:02, Roger Pau Monné wrote: >>> On Fri, May 16, 2025 at 09:07:43AM +0200, Jan Beulich wrote: >>>> On 15.05.2025 12:28, Roger Pau Monné wrote: >>>>> On Mon, May 12, 2025 at 05:16:02PM +0200, Jan Beulich wrote: >>>>>> On 06.05.2025 10:31, Roger Pau Monne wrote: >>>>>>> To better describe the underlying implementation. Define >>>>>>> cache_flush_permitted() as an alias of has_arch_io_resources(), so that >>>>>>> current users of cache_flush_permitted() are not effectively modified. >>>>>>> >>>>>>> With the introduction of the new handler, change some of the call sites >>>>>>> of >>>>>>> cache_flush_permitted() to instead use has_arch_io_resources() as such >>>>>>> callers are not after whether cache flush is enabled, but rather whether >>>>>>> the domain has any IO resources assigned. >>>>>>> >>>>>>> Take the opportunity to adjust l1_disallow_mask() to use the newly >>>>>>> introduced has_arch_io_resources() macro. >>>>>> >>>>>> While I'm happy with everything else here, to me it's at least on the >>>>>> edge whether cache_flush_permitted() wouldn't be the better predicate >>>>>> to use there, for this being about ... >>>>>> >>>>>>> --- a/xen/arch/x86/mm.c >>>>>>> +++ b/xen/arch/x86/mm.c >>>>>>> @@ -172,8 +172,7 @@ static DEFINE_SPINLOCK(subpage_ro_lock); >>>>>>> >>>>>>> #define l1_disallow_mask(d) \ >>>>>>> (((d) != dom_io) && \ >>>>>>> - (rangeset_is_empty((d)->iomem_caps) && \ >>>>>>> - rangeset_is_empty((d)->arch.ioport_caps) && \ >>>>>>> + (!has_arch_io_resources(d) && \ >>>>>>> !has_arch_pdevs(d) && \ >>>>>>> is_pv_domain(d)) ? \ >>>>>>> L1_DISALLOW_MASK : (L1_DISALLOW_MASK & ~PAGE_CACHE_ATTRS)) >>>>>> >>>>>> ... cachability, which goes hand in hand with the ability to also >>>>>> flush cache contents. >>>>> >>>>> Hm, I was on the edge here, in fact I've previously coded this using >>>>> cache_flush_permitted(), just to the change back to >>>>> has_arch_io_resources(). If you think cache_flush_permitted() is >>>>> better I'm fine with that. >>>> >>>> I think that would be better here, yet as you say - it's not entirely >>>> clear cut either way. >>> >>> I've reverted this chunk of the change and left the code as-is for the >>> time being. >> >> Didn't we agree to use cache_flush_permitted() here instead? > > I think it would be a bit weird, if we want this to be a > non-functional change we would need to keep the has_arch_pdevs() > condition because cache_flush_permitted() doesn't take that into > account. Or we need to adjust cache_flush_permitted() to also take > has_arch_pdevs() into consideration.
Which is what you suggested elsewhere, or did I misunderstand that? Jan
