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

Jason Gunthorpe
2020-09-17T11:38:07Z

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

Jason