Re: [PATCH v2] PCI/MSI: Correct use of can_mask in msi_add_msi_desc()

[Bjorn Helgaas <helgaas@kernel.org>]

On Mon, Feb 14, 2022 at 11:07:47AM +0100, Josef Johansson wrote:
> From: Josef Johansson <josef@oderland.se>
> 
> PCI/MSI: Correct use of can_mask in msi_add_msi_desc()
>     
> Commit 71020a3c0dff4 ("PCI/MSI: Use msi_add_msi_desc()") modifies
> the logic of checking msi_attrib.can_mask, without any reason.
>     
> This commits restores that logic.
> 
> Fixes: 71020a3c0dff4 ("PCI/MSI: Use msi_add_msi_desc()")
> Signed-off-by: Josef Johansson <josef@oderland.se>

Applied to pci/misc for v6.1 with commit log below, thanks!

  PCI/MSI: Correct 'can_mask' test in msi_add_msi_desc()

  71020a3c0dff4 ("PCI/MSI: Use msi_add_msi_desc()") inadvertently reversed
  the sense of "msi_attrib.can_mask" in one use:

    - if (entry->pci.msi_attrib.can_mask) {
    -         addr = pci_msix_desc_addr(entry);
    -         entry->pci.msix_ctrl = readl(addr + PCI_MSIX_ENTRY_VECTOR_CTRL);
    + if (!desc.pci.msi_attrib.can_mask) {
    +         addr = pci_msix_desc_addr(&desc);
    +         desc.pci.msix_ctrl = readl(addr + PCI_MSIX_ENTRY_VECTOR_CTRL);

  Restore the original test.

> ---
> v2: Changing subject line to fit earlier commits.
> 
> Trying to fix a NULL BUG in the NVMe MSIX implementation I stumbled upon this code,
> which ironically was what my last MSI patch resulted into.
> 
> I don't see any reason why this logic was change, and it did not break anything
> correcting the logic.
> 
> CC xen-devel since it very much relates to Xen kernel (via pci_msi_ignore_mask).
> ---
> 
> diff --git a/drivers/pci/msi/msi.c b/drivers/pci/msi/msi.c
> index c19c7ca58186..146e7b9a01cc 100644
> --- a/drivers/pci/msi/msi.c
> +++ b/drivers/pci/msi/msi.c
> @@ -526,7 +526,7 @@ static int msix_setup_msi_descs(struct pci_dev *dev, void __iomem *base,
>  		desc.pci.msi_attrib.can_mask = !pci_msi_ignore_mask &&
>  					       !desc.pci.msi_attrib.is_virtual;
>  
> -		if (!desc.pci.msi_attrib.can_mask) {
> +		if (desc.pci.msi_attrib.can_mask) {
>  			addr = pci_msix_desc_addr(&desc);
>  			desc.pci.msix_ctrl = readl(addr + PCI_MSIX_ENTRY_VECTOR_CTRL);
>  		}
> 
> --
> 2.31.1
> 
>