Hi Oleksandr, > On 29 Jul 2022, at 5:28 pm, Oleksandr <olekst...@gmail.com> wrote: > > > Hello Rahul > > > On 19.07.22 20:42, Oleksandr Tyshchenko wrote: >> From: Oleksandr Andrushchenko <oleksandr_andrushche...@epam.com> >> >> Add a stub for is_memory_hole which is required for PCI passthrough >> on Arm. >> >> Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushche...@epam.com> >> --- >> OT: It looks like the discussion got stuck. As I understand this >> patch is not immediately needed in the context of current series >> as PCI passthrough is not enabled on Arm at the moment. So the patch >> could be added later on, but it is needed to allow PCI passthrough >> to be built on Arm for those who want to test it. >> >> Copy here some context provided by Julien: >> >> Here a summary of the discussion (+ some my follow-up thoughts): >> >> is_memory_hole() was recently introduced on x86 (see commit 75cc460a1b8c >> "xen/pci: detect when BARs are not suitably positioned") to check >> whether the BAR are positioned outside of a valid memory range. This was >> introduced to work-around quirky firmware. >> >> In theory, this could also happen on Arm. In practice, this may not >> happen but it sounds better to sanity check that the BAR contains >> "valid" I/O range. >> >> On x86, this is implemented by checking the region is not described is >> in the e820. IIUC, on Arm, the BARs have to be positioned in pre-defined >> ranges. So I think it would be possible to implement is_memory_hole() by >> going through the list of hostbridges and check the ranges. >> >> But first, I'd like to confirm my understanding with Rahul, and others. > > > May I please ask about your opinion on that?
I agree with Julien we can implement the something similar to is_memory_hole() for ARM that will check that the bar is within the bridge ranges. If you are okay you can discard this patch in next version of the series and I will push the patch for review. Regards, Rahul
