linux-kernel - revert bab65e48cb064 PCI/MSI Sanitize MSI-X checks

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Date:   Thu, 6 Apr 2023 11:05:14 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Thomas Gleixner" <tglx@...utronix.de>,
        Jason Gunthorpe <jgg@...dia.com>,
        "Bjorn Helgaas" <bhelgaas@...gle.com>
CC:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Christoph Hellwig <hch@...radead.org>
Subject: revert bab65e48cb064 PCI/MSI Sanitize MSI-X checks

The change in bab65e48cb064 breaks pci_enable_msix_range().
The intent is to optimise the sanity checks, but it is
somewhat overenthusiastic.

The interface allows you to ask for a lot of vectors and
returns the number that were allocated.
However, after the change, you can't request a vector
that is higher than the largest the hardware supports.
Which makes that rather pointless.

So code like:
	for (i = 0; i < 16; i++)
		msix_tbl[i].entry = i;
	nvec = pci_enable_msix_range(dev, msix_tbl, 1, 16);
Now returns -22 if the hardware only supports 8 interrupts.

Previously it returned 8.

I can fix my driver, but I suspect that any code that relies
on a smaller number of vectors being returned is now broken.

	David

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