On Tue, 26 Nov 2024 19:12:35 -0600 Mitchell Augustin <mitchell.augustin@xxxxxxxxxxxxx> wrote: > Thanks for the breakdown! > > > That alone calls __pci_read_base() three separate times, each time > > disabling and re-enabling decode on the bridge. [...] So we're > > really being bitten that we toggle decode-enable/memory enable > > around reading each BAR size > > That makes sense to me. Is this something that could theoretically be > done in a less redundant way, or is there some functional limitation > that would prevent that or make it inadvisable? (I'm still new to pci > subsystem debugging, so apologies if that's a bit vague.) The only requirement is that decode should be disabled while sizing BARs, the fact that we repeat it around each BAR is, I think, just the way the code is structured. It doesn't take into account that toggling the command register bit is not a trivial operation in a virtualized environment. IMO we should push the command register manipulation up a layer so that we only toggle it once per device rather than once per BAR. Thanks, Alex
