On Tue, Apr 21, 2020 at 10:25:49AM +0100, Peter Maydell wrote: > On Tue, 21 Apr 2020 at 10:16, Gerd Hoffmann <kra...@redhat.com> wrote: > > cirrus stopped using pointers years ago, exactly for the reasons > > outlined above. Conversion was pretty straight forward. > > > > commit 026aeffcb4752054830ba203020ed6eb05bcaba8 > > Author: Gerd Hoffmann <kra...@redhat.com> > > Date: Wed Mar 15 11:47:52 2017 +0100 > > > > cirrus: stop passing around dst pointers in the blitter > > > > Instead pass around the address (aka offset into vga memory). Calculate > > the pointer in the rop_* functions, after applying the mask to the > > address, to make sure the address stays within the valid range. > > Aha, thanks for bringing up the prior art. (Did anybody benchmark > whether there was a noticeable performance impact for that cirrus > change? My guess is that there wouldn't be much/any because the memory > operations will dominate and you get to do the masking operation more > or less for free, but guesses are notoriously unreliable when it > comes to performance :-) )
In case of the cirrus the first problem is finding an guest which is old enough that it actually uses the blitter ;) So, in 99% of the cases the difference is zero due to the blitter not being used by the guest. And, no, I don't have numbers for the remaining 1%. take care, Gerd
