> From: Jan Beulich <[email protected]> > Sent: Thursday, December 2, 2021 4:48 PM > > On 01.12.2021 14:02, Andrew Cooper wrote: > > On 01/12/2021 09:41, Jan Beulich wrote: > >> --- a/xen/drivers/passthrough/vtd/iommu.c > >> +++ b/xen/drivers/passthrough/vtd/iommu.c > >> @@ -591,7 +591,8 @@ static int __must_check iommu_flush_all( > >> bool_t flush_dev_iotlb; > >> int rc = 0; > >> > >> - flush_all_cache(); > >> + flush_local(FLUSH_CACHE); > > > > While I agree that the conversion is an improvement, the logic still > > looks totally bogus. > > > > I can believe that it might have been a stopgap to fix problems before > > we identified the need for sync_cache() for non-coherent IOMMUs, but > > there's no need I can spot for any WBINVDs on any of these paths. > > > > I'm fairly sure this should just be dropped, and Xen will get faster as > > a result. > > Kevin, thoughts? I have to admit I'm hesitant to remove such code, when > there's no clear indication why it's there. I'm also not sure how much > of a win the dropping would be, considering the places where this > function gets called from. >
me too. Could Andrew elaborate further on "fairly sure" part? Thanks Kevin
