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From:   Heiner Kallweit <hkallweit1@gmail.com>
To:     Marc Zyngier <maz@kernel.org>, Thomas Gleixner <tglx@linutronix.de>
Cc:     Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        "linux-nvme@lists.infradead.org" <linux-nvme@lists.infradead.org>,
        Christoph Hellwig <hch@lst.de>
Subject: linux-next: NVME using PCI legacy interrupts only
Message-ID: <52371274-20bc-a150-a3ed-ba3e1305ad3e@gmail.com>
Date:   Wed, 9 Jun 2021 20:43:57 +0200
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I found that on linux-next from June 8th my nvme disk is using legacy
interrupts only. Some debugging lead me to irq_find_mapping() in
msi_domain_alloc() returning -EEXIST.

The nvme core first allocates a MSI-X interrupt for setup purposes
and later frees it and allocates the final number of MSI-X interrupts.

The following experimental change brought back the MSI-X interrupts.
This makes me think that somehow freeing a MSI-X interrupt doesn't
free it completely. I didn't see this behavior a few days ago,
therefore I think it's related to the recent changes to
irqdomain/genirq.

Didn't do a bisect yet, maybe you have an idea already.

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index a29b17070..8cc600819 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -2381,7 +2381,7 @@ static int nvme_pci_enable(struct nvme_dev *dev)
         * interrupts. Pre-enable a single MSIX or MSI vec for setup. We'll
         * adjust this later.
         */
-       result = pci_alloc_irq_vectors(pdev, 1, 1, PCI_IRQ_ALL_TYPES);
+       result = pci_alloc_irq_vectors(pdev, 1, 1, PCI_IRQ_LEGACY);
        if (result < 0)
                return result;