linux-kernel - [PATCH v2 01/15] PCI/MSI: Forward MSI-X vector enable error code in pci_alloc_irq_vectors

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Date:   Wed,  3 Jun 2020 13:44:24 +0200
From:   Piotr Stankiewicz <piotr.stankiewicz@...el.com>
To:     Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org
Cc:     Piotr Stankiewicz <piotr.stankiewicz@...el.com>,
        Andy Shevchenko <andriy.shevchenko@...el.com>,
        Logan Gunthorpe <logang@...tatee.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Jian-Hong Pan <jian-hong@...lessm.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2 01/15] PCI/MSI: Forward MSI-X vector enable error code in pci_alloc_irq_vectors_affinity()

When debugging an issue where I was asking the PCI machinery to enable a
set of MSI-X vectors, without falling back on MSI, I ran across a
behaviour which seems odd. The pci_alloc_irq_vectors_affinity() will
always return -ENOSPC on failure, when allocating MSI-X vectors only,
whereas with MSI fallback it will forward any error returned by
__pci_enable_msi_range(). This is a confusing behaviour, so have the
pci_alloc_irq_vectors_affinity() forward the error code from
__pci_enable_msix_range() when appropriate.

Signed-off-by: Piotr Stankiewicz <piotr.stankiewicz@...el.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@...el.com>
---
 drivers/pci/msi.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
index 6b43a5455c7a..443cc324b196 100644
--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c
@@ -1231,8 +1231,9 @@ int pci_alloc_irq_vectors_affinity(struct pci_dev *dev, unsigned int min_vecs,
 		}
 	}
 
-	if (msix_vecs == -ENOSPC)
-		return -ENOSPC;
+	if (msix_vecs == -ENOSPC ||
+	    (flags & (PCI_IRQ_MSI | PCI_IRQ_MSIX)) == PCI_IRQ_MSIX)
+		return msix_vecs;
 	return msi_vecs;
 }
 EXPORT_SYMBOL(pci_alloc_irq_vectors_affinity);
-- 
2.17.2