On Wed, Dec 16, 2020 at 06:49:54PM +0100, Marek Vasut wrote: > On 12/14/20 5:08 PM, Lorenzo Pieralisi wrote: > > On Sat, Dec 12, 2020 at 08:13:54PM +0100, Marek Vasut wrote: > > > On 12/10/20 7:11 PM, Lorenzo Pieralisi wrote: > > > > > > [...] > > > > > > > > diff --git a/drivers/pci/controller/pcie-rcar-host.c b/drivers/pci/controller/pcie-rcar-host.c > > > > > index 1194d5f3341b..ac5c7d7573a6 100644 > > > > > --- a/drivers/pci/controller/pcie-rcar-host.c > > > > > +++ b/drivers/pci/controller/pcie-rcar-host.c > > > > > @@ -753,7 +753,7 @@ static int rcar_pcie_enable_msi(struct rcar_pcie_host *host) > > > > > } > > > > > /* setup MSI data target */ > > > > > - msi->pages = __get_free_pages(GFP_KERNEL, 0); > > > > > + msi->pages = __get_free_pages(GFP_KERNEL | GFP_DMA32, 0); > > > > > > > > This does not do what you want on !CONFIG_ZONE_DMA32 (ie arm LPAE). > > > > > > How come? I would expect GFP_DMA32 allocates a buffer below 4 GiB in any > > > case. > > > > For ARM LPAE allocation falls back to ZONE_NORMAL that happens to work > > because if there is memory > 4GB it ends up in ZONE_HIGHMEM, so this > > patch should still work on ARM LPAE too. > > > > Regardless, thoughts above the alternative approach (that saves you > > a page allocation) ? > > Since this is a bugfix, I would prefer it to be minimal. Yes, I agree with you on that. > Also, in case there was some yet undiscovered hardware bug which would > let the MSI write through, having unused memory as the MSI destination > address would only lead to write into that memory -- instead of a > write into some other address. > > Changing this to some hard-coded address (any suggestions?) can be a > subsequent patch. The idea was taking the address from the host controller inbound window (ie an address outside the dma-ranges ~(dma-ranges) and < 4GB), it should not matter which one. I agree though that this can be a subsequent patch even though usually we send for -rc* only fixes for patches that hit the previous merge window - this seems a quite longstanding (I traced it back to v3.16) one so it would wait till v5.12, there is time to refactor it. Thanks, Lorenzo
