Re: [PATCH] PCI/MSI: msix_setup_msi_descs: Restore logic for msi_attrib.can_mask

[Bjorn Helgaas <helgaas@kernel.org>]

[+cc Jason, since you reviewed the original commit]

On Sat, Jan 22, 2022 at 02:10:01AM +0100, Josef Johansson wrote:
> From: Josef Johansson <josef@oderland.se>
> 
> PCI/MSI: msix_setup_msi_descs: Restore logic for msi_attrib.can_mask

Please match the form and style of previous subject lines (in
particular, omit "msix_setup_msi_descs:").

> 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.

I agree, this looks like a typo in 71020a3c0dff4, but I might be
missing something, so Thomas should take a look, and I added Jason
since he reviewed it.

Since it was merged by Thomas, I'll let him take care of this, too.
If it *is* a typo, the fix looks like v5.17 material.

Before: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/pci/msi/msi.c?id=71020a3c0dff4%5E#n522
After:  https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/pci/msi/msi.c?id=71020a3c0dff4#n520

> Fixes: 71020a3c0dff4 ("PCI/MSI: Use msi_add_msi_desc()")
> Signed-off-by: Josef Johansson <josef@oderland.se>
> 
> ---
> 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, nor do I have the possibility
> to see if anything works with my patch or without, since the kernel crashes
> in other places.
> 
> As such this is still untested, but as far as I can tell it should restore
> functionality.
> 
> Re-sending since it was rejected by linux-pci@vger.kernel.org due to HTML contents.
> Sorry about that.
> 
> 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
>