[tip: irq/urgent] PCI/MSI: Mask MSI-X vectors only on success

["tip-bot2 for Stefan Roese" <tip-bot2@linutronix.de>]

The following commit has been merged into the irq/urgent branch of tip:

Commit-ID:     83dbf898a2d45289be875deb580e93050ba67529
Gitweb:        https://git.kernel.org/tip/83dbf898a2d45289be875deb580e93050ba67529
Author:        Stefan Roese <sr@denx.de>
AuthorDate:    Tue, 14 Dec 2021 12:49:32 +01:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Tue, 14 Dec 2021 13:23:32 +01:00

PCI/MSI: Mask MSI-X vectors only on success

Masking all unused MSI-X entries is done to ensure that a crash kernel
starts from a clean slate, which correponds to the reset state of the
device as defined in the PCI-E specificion 3.0 and later:

 Vector Control for MSI-X Table Entries
 --------------------------------------

 "00: Mask bit:  When this bit is set, the function is prohibited from
                 sending a message using this MSI-X Table entry.
                 ...
                 This bit’s state after reset is 1 (entry is masked)."

A Marvell NVME device fails to deliver MSI interrupts after trying to
enable MSI-X interrupts due to that masking. It seems to take the MSI-X
mask bits into account even when MSI-X is disabled.

While not specification compliant, this can be cured by moving the masking
into the success path, so that the MSI-X table entries stay in device reset
state when the MSI-X setup fails.

[ tglx: Move it into the success path, add comment and amend changelog ]

Fixes: aa8092c1d1f1 ("PCI/MSI: Mask all unused MSI-X entries")                                                                                                                                                                                                                 
Signed-off-by: Stefan Roese <sr@denx.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-pci@vger.kernel.org
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Michal Simek <michal.simek@xilinx.com>
Cc: Marek Vasut <marex@denx.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20211210161025.3287927-1-sr@denx.de
---
 drivers/pci/msi.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
index 48e3f4e..6748cf9 100644
--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c
@@ -722,9 +722,6 @@ static int msix_capability_init(struct pci_dev *dev, struct msix_entry *entries,
 		goto out_disable;
 	}
 
-	/* Ensure that all table entries are masked. */
-	msix_mask_all(base, tsize);
-
 	ret = msix_setup_entries(dev, base, entries, nvec, affd);
 	if (ret)
 		goto out_disable;
@@ -751,6 +748,16 @@ static int msix_capability_init(struct pci_dev *dev, struct msix_entry *entries,
 	/* Set MSI-X enabled bits and unmask the function */
 	pci_intx_for_msi(dev, 0);
 	dev->msix_enabled = 1;
+
+	/*
+	 * Ensure that all table entries are masked to prevent
+	 * stale entries from firing in a crash kernel.
+	 *
+	 * Done late to deal with a broken Marvell NVME device
+	 * which takes the MSI-X mask bits into account even
+	 * when MSI-X is disabled, which prevents MSI delivery.
+	 */
+	msix_mask_all(base, tsize);
 	pci_msix_clear_and_set_ctrl(dev, PCI_MSIX_FLAGS_MASKALL, 0);
 
 	pcibios_free_irq(dev);