[PATCH] arm64: Enable PCI write-combine resources under sysfs

Lorenzo Pieralisi lorenzo.pieralisi at arm.com
Thu Sep 17 10:01:16 EDT 2020


On Thu, Sep 17, 2020 at 08:32:21AM -0300, Jason Gunthorpe wrote:
> On Thu, Sep 17, 2020 at 11:28:19AM +0100, Lorenzo Pieralisi wrote:
> > Unfortunately if we merge this patch we _do_ know from this thread
> > that userspace will suffer from a perf regression on TX2.
> > 
> > Either we ignore it or we write some code to prevent it
> > (ie first step make arch_can_pci_mmap_wc() return 0 on TX2 -
> > possibly using the arm64 errata detection mechanism).
> 
> If anyone complains they can send the change to arch_can_pci_mmap_wc()
> - I'm pretty sure nobody will complain due to mlx5

If that's the case we can go ahead and merge this patch with a
reworded commit log - this thread was very useful nonetheless
for my own information (and others hopefully) so thank you.

For VFIO WC + "message push ioremap" - to be continued.

Clint, please reword the commit and resend, not sure we can hit
v5.10 but we shall try.

Thanks,
Lorenzo



More information about the linux-arm-kernel mailing list